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The Case for Requiring Rear Lighting at Night

The bicycle law study committee created by the enactment of HB232 had its first meeting August 7, when it identified priority safety issues to examine. One change to state traffic law that BikeWalk NC has recommended is that night lighting requirements for bicyclists be upgraded to require a rear lamp.

Cycling in darkness is important for commuting and other forms of utility cycling. Visibility is a concern, however. About 1/4 of car/bike collisions in North Carolina happen at night, including about one half of all bicyclist fatalities. Black and Hispanic bicyclists represent over half of night car-bike collisions in our state. Most bicyclists involved in crashes in darkness are not using lights.

Existing North Carolina law for night bicycling requires a headlamp in front and either a reflector or lamp in the rear, as follows:

20-129.(e) Lamps on Bicycles. – Every bicycle shall be equipped with a lighted lamp on the front thereof, visible under normal atmospheric conditions from a distance of at least 300 feet in front of such bicycle, and shall also be equipped with a reflex mirror or lamp on the rear, exhibiting a red light visible under like conditions from a distance of at least 200 feet to the rear of such bicycle, when used at night.

All US states require a white headlamp when bicycling at night. Currently five states require a red rear lamp: Alaska, Florida, New Jersey, New York, and Ohio. Three of these, Alaska, Florida, and Ohio, require a rear reflector in addition to a rear lamp. The other US states allow an option between a rear lamp or rear reflector.

State Rear Lamp Visibility Distance Reflector Also Required
Alaska 500 feet Yes
Florida 600 feet Yes
New Jersey 500 feet No
New York 300 feet No
Ohio 500 feet Yes

Most European countries require a white front lamp, a red rear lamp, AND a red rear reflector. Sweden specifies 300 meter (984 feet) visibility for front and rear lamps. Most LED bike lamps are visible at 1000 feet.

Night Crash Types

nightcollisionschart

Types and frequency of car-bike crashes at night in North Carolina

A headlamp is essential to avoiding many common types of car-bike collisions, which involve other drivers pulling out or turning left in front of the bicyclist at junctions. These drivers’ headlamps won’t illuminate the bicycle and its reflectors until it’s too late. Only the projected beam of the bicyclist’s own headlamp will make the bicyclist visible to drivers on intersecting paths.

driveoutleftcross

Visibility at junctions

Car-overtaking-bicycle collisions comprise 25% of night bicycling crashes, versus 11% of daytime crashes.  Most overtaking crashes occur on roads posted 40mph or higher. This means that drivers must be able to detect and recognize the reflector at a long distance away in order to have time to take appropriate actions such as braking or changing lanes to pass safely. Unfortunately, the stock reflectors sold with new bicycles (mandated by the Consumer Products Safety Commission, aka CPSC) are small and very dim when viewed under headlamps at long distances.

Distance Matters

How far away should a bicyclist be visible from behind? The AASHTO Policy on Geometric Design of Highways and Streets provides a useful concept of Decision Sight Distance, defined as follows: “the distance needed for a driver to detect an unexpected or otherwise difficult-to-perceive information sources or condition in a roadway environment that may be visually cluttered, recognize the condition or its potential threat, select an appropriate speed and path, and initiate and complete the maneuver safety and efficiently.”  A road posted with a 40 or 45 mph speed limit will typically have a design speed of 45 to 50 miles per hour. According to the AASHTO guide, the decision sight distances recommended for stopping or changing speeds or direction range from 800 to 1030 feet on urban and suburban roads, and from 395 to 750 feet on rural roads. This is far longer than the visibility distance of 200 feet currently required under state law. Note that the emergency stopping distance for a car driver traveling 45 mph is nearly 200 feet when including reaction time. This leaves no room for distraction or recognition lag.

decisionsightdistance

2004 AASHTO Policy on Geometric Design of Highways and Streets, page 115

An Experiment

So how far away is a typical bike reflector really visible, and how much better is a rear lamp? BikeWalk NC decided to put this to a test by setting up two LED bike lamps, a highway marker reflector, and a CPSC bike reflector on a white board and viewing it under car headlamps at different distances. Photos were taken from inside the vehicle, behind the windshield using a DSLR camera with a telephoto lens and set for a fixed speed that approximated human perception. At 50 feet, the CPSC bike reflector appeared roughly as bright as a bargain-priced LED bike lamp. At increasing distance, however, the bike reflector grew much dimmer than both of the LED lamps, as shown below.

lighttestcomparison

Rear visibility equipment test at various ranges. (a) Planet Bike Superflash in steady mode. (b) Bargain LED bike light. (c) Amber automotive/marker reflector. (d) CPSC bike reflector.

During the experiment, the bike reflector would virtually disappear even at short ranges with changes in headlamp orientation that resulted from minor changes in roadway grade (the street was not perfectly flat) or by turning the vehicle slightly. The height and position of the test devices were manually adjusted to compensate as much as possible, but the sensitivity to headlamp orientation was quite alarming.

The LED lamps were then switched to blinking mode, and video was recorded at 300 feet:

Lights versus Reflectors under Car Headlamps at 300 Feet

As shown, LED lamps are far more visible and conspicuous than reflectors at long distances. An LED lamp stands out better among other nearby vehicle lights (clutter) than does reflected power at long range. And given the video experiment, it’s no wonder why many cyclists think blinking LED lamps further increase distances for recognition as a bicyclist.

Optional: A Physics Lesson

At 500 feet, observed LED power can be 100x greater than observed reflector power.  This is because reflected light coming off a bike reflector declines in power with distance by a different exponent than light coming from an LED lamp. If the range between the bicyclist and driver is R, then the LED light power reaching the driver declines proportional to 1/R^2. But for a reflector, the light power declines proportional to 1/R^4.

physicslamp

physicsreflector

Reflectors have other weaknesses. Car headlights may not be on or working, and curves and hill crests affect beam orientation. As shown below, a bicyclist’s reflectors may not be illuminated until the last moment.

reflectorcurve

Disadvantages of Lights

Lights have their own issues as well. They require power, their batteries go dead, they are more expensive, and they can get stolen off of a parked bike. Bike lamps can also fail by breaking or popping open when hitting a pothole, or by shorting out in wet conditions. Unfortunately, failures are especially common with the least expensive, discount lamps that use brittle plastic for the housing or mount. Should a failure happen while you are riding, you may not even notice it, since the lamp is behind you. It’s important to use a rear reflector as an emergency backup just in case.

Bright LED tail lamps are available new for under $10. Unfortunately, some of these bargain lamps are of poor durability, and can snap off at the mounting bracket after one or two bumps. Others are cheap to buy but expensive to maintain because they use coin cell batteries. AAA batteries are more economical than coin cells over the life of the lamp, but rechargeable systems can be the best deal in the long run.

Bicycle headlamps are typically much brighter than tail lamps, because bike headlamps are normally used to illuminate the roadway itself, while tail lamps are just for visibility to others. The difference in power requirements means that tail lamps are usually less expensive than headlamps.

Enforcement and Education Concerns

BikeWalk NC does not take the idea of new bicycling regulations lightly. The cost and convenience of maintaining a rear lamp must be weighed against the safety benefits. Given the relative affordability of LED tail lamps and the high percentage of serious crashes involving unlighted cyclists hit from behind at night, it is the BikeWalk NC Board of Directors’ position that changing state law to require a rear lamp when bicycling at night will improve awareness of effective visibility equipment, increase bicyclist safety and save lives at a reasonable equipment cost.

Bikewalk NC recommends that such a legal change be accompanied by a comprehensive education campaign on night visibility for bicyclists using a variety of media. Enforcement actions should be focused on empowering bicyclists to get home safely through the use of lighting giveaways or by providing assistance at finding alternative transportation home. Funding needs to be secured to persist lighting giveaway programs, especially in low income areas. Sensitivity to minority perceptions of police activity will be vitally important in the execution of a safety campaign. Historically, police enforcement of bicycle lighting laws in North Carolina has most often been performed as a pretext to stop, question, and potentially search people, usually minorities. Pretextual stops of bicyclists riding at night without lights or without city registration have inflamed racial tensions in Tampa and other cities such as Miami, Fort Lauderdale and Washington DC. A change in the state’s bicycle lighting law must serve to protect minority bicyclists, not provide another way to victimize them.

BikeWalk NC Recommended Statute Change

20-129.(e) Lamps on Bicycles. – Every bicycle shall be equipped with a lighted lamp on the front thereof, visible under normal atmospheric conditions from a distance of at least 1000 feet in front of such bicycle, and shall also be equipped with a reflex mirror and lamp on the rear, exhibiting a red light visible under like conditions from a distance of at least 1000 feet to the rear of such bicycle, when used at night.

See Also

Requirements on Lighting and Reflectors of Bicycles, ANEC, 2012. http://www.anec.eu/attachments/anec-r&t-2012-traf-002.pdf
Bicycle Reflector Project, CPSC, 1996. http://www.cpsc.gov//PageFiles/117813/BikeReport.pdf
About Bicycle Reflectors, John Allen, 2001, 2014. http://www.bikexprt.com/bicycle/reflectors/
Why Reflectors Don’t Work, John Schubert, http://www.sheldonbrown.com/reflectors.html

HB232 Bicycle Safety Law Study – Working Group Discusses Safety Benefits of Riding Two Abreast – No Legislation Recommended to Limit This Existing Right

doublfilephoto

 

The Working Group brought together by NCDOT pursuant to House Bill 232 to study bicycle safety laws held their final meeting November 18th. The group focused on the legislative directive to look at whether cyclists should be required to ride single file or allowed to ride two or more abreast. The committee unanimously approved a motion to recommend no new regulations on riding abreast and instead for NCDOT to develop an education and outreach program (with funding) to promote safe group riding practices, safe cycling, and safe motoring, including advice spelled out in the resolution drafted by NCDOT that the preferred method of passing bicyclists is a lane-change pass.

The consensus was that riding two abreast is often safer than single file.  Here are some points made during the discussion.

  • James Gallagher (UNC Highway Safety Research Center) and enforcement representative Chris Knox both scoured general statutes and reached out to experts and did not find anything that prohibits riding two or more abreast.
  • Absent law against, cyclists riding two or more abreast is legal.  Steve Goodridge (BWNC) pointed out that a few municipalities in NC have traffic laws that may conflict with state law as they place restrictions on riding abreast or require riding single file.
  • James Gallagher also searched research and found none that suggested riding single file is safer.
  • Each person on the committee was asked to share their view for the record on riding two abreast. No one thought it was safer or provided rationale to support requiring single file.  Virtually all shared thoughts that supported riding two abreast such as:
    • No recorded hits from behind when riding two abreast. Numerous single file riders have been hit from behind.
    • Riding two abreast makes the bicyclists more visible, appear “bigger”
    • Riding two abreast makes motorist pass in other lane, which is safer (most crashes are from same lane passing)
    • Riding two abreast tightens group and thus facilitates passing for motorists
    • Gallagher added that only 3 states restrict it (39 states specifically allow it)

The committee had previously taken action on some of the other legislative directives – here is a summary of actions taken from previous meetings.   Recommended legislation included:

  • Allowing crossing of solid yellow line to pass bicyclists when safe
  • Requiring rear lighting or reflective clothing

Thank you to our cycling supporters that attended the meeting; some came in from Charlotte.

NCDOT will now assemble the committee recommendations into a report document, and write its official legislative recommendations into that document. The draft report and recommendations will be made available for public comment and likely revisions before being provided to the legislature. BikeWalk NC and the cycling community will need to pay close attention to the report document, but even more important is what the legislature decides to do with it.

BikeWalk NC Presentations to the HB232 Study Committee

BikeWalk NC Board member Steven Goodridge is serving on the HB232 bike safety law study committee in order to support cyclists’ interests and present information on best bicycling practices to the committee. Below are materials BikeWalk NC has presented to the committee:

Background Papers:

Evolution of Stay-Right Laws (PDF)

Passing Laws (PDF)

Best Bicycle Driving Practices and North Carolina Law (PDF)

Slide Presentation: Safe Passing and Riding Abreast (Presented 9/11/2015)

PDF File

Blog Articles:

Night Visibility, Rear Lighting (Blog Article)

What is a Courteous Cyclist? (Blog Article)

 

Additional presentations are planned, should time allow.

Motoring: First Come, First Served

Assured Clear Distance Ahead

Faster drivers must yield to slower and stopped traffic ahead. All vehicle operators must travel no faster than is safe and will allow them to stop within their sight distance. This legal principle is known as assured clear distance ahead.

“The Assured Clear Distance Ahead (ACDA) is the distance ahead of a vehicle or craft which can be seen to be clear of hazards by the driver, within which they should be able to bring the vehicle to a halt. It is one of the most fundamental principles governing ordinary care and the duty of care and is frequently used to determine if a driver is in proper control and is a nearly universally implicit consideration in vehicular accident liability.”

The North Carolina Driver’s Handbook provides guidance on this:

“The faster you are moving, the farther ahead you must be able to see to allow enough distance for stopping.” (p. 46)

“Never drive at a speed at which you cannot stop within the distance you can see on the road ahead” (p. 62)

Slow or stopped traffic may be present on any road at any time. Drivers must always be prepared to encounter garbage trucks, school buses, farm tractors, construction equipment, police officers, pedestrians,  bicyclists and traffic congestion on most roads. Driving in a way that would endanger other road users who are stopped or traveling slowly is unlawful.

§ 20-141. Speed restrictions. (a) No person shall drive a vehicle on a highway or in a public vehicular area at a speed greater than is reasonable and prudent under the conditions then existing. … (m) The fact that the speed of a vehicle is lower than the foregoing limits shall not relieve the operator of a vehicle from the duty to decrease speed as may be necessary to avoid colliding with any person, vehicle or other conveyance on or entering the highway, and to avoid injury to any person or property.

§ 20-140. Reckless driving. (b) Any person who drives any vehicle upon a highway or any public vehicular area without due caution and circumspection and at a speed or in a manner so as to endanger or be likely to endanger any person or property shall be guilty of reckless driving.

Most drivers have no difficulty limiting their speed and seeing and slowing in time to avoid hitting vehicles traveling slowly ahead on the roadway. Impaired driving, reckless driving, distracted driving and bicycling at night without an adequate rear light or reflector are the primary contributing factors in car-bike collisions where motorists fail to slow in time to avoid rear-ending slower bicyclists.

Traffic Bicycling: 1. First Come, First Served

1. First Come, First Served

Faster drivers must yield to slower and stopped traffic ahead. All vehicle operators must travel no faster than is safe and will allow them to stop within their sight distance. This legal principle is known as assured clear distance ahead. As a bicyclist, you have a right to use the roadway, and other drivers are legally required to respect your right of way, but you must act visibly and predictably to allow them to do so.

Each driver who is already on the road is entitled to the space their vehicle occupies, plus reasonable clearance behind and to each side, and reasonable stopping distance in front of them. Drivers must yield to other drivers already on the road in front of them, which requires them to limit their speed and be prepared to slow or stop for other traffic ahead.

§ 20-141. Speed restrictions. (a) No person shall drive a vehicle on a highway or in a public vehicular area at a speed greater than is reasonable and prudent under the conditions then existing. … (m) The fact that the speed of a vehicle is lower than the foregoing limits shall not relieve the operator of a vehicle from the duty to decrease speed as may be necessary to avoid colliding with any person, vehicle or other conveyance on or entering the highway, and to avoid injury to any person or property.

§ 20-140. Reckless driving. (b) Any person who drives any vehicle upon a highway or any public vehicular area without due caution and circumspection and at a speed or in a manner so as to endanger or be likely to endanger any person or property shall be guilty of reckless driving.

Most drivers have no difficulty limiting their speed and seeing and slowing in time to avoid hitting vehicles traveling slowly ahead on the roadway. Impaired driving, reckless driving, distracted driving and bicycling at night without an adequate rear light or reflector are the primary contributing factors in car-bike collisions where motorists fail to slow in time to avoid rear-ending slower bicyclists. Fortunately, there’s a lot you can do to improve the reliability with which drivers see and yield to you. Always use front and rear lights when cycling at night, and be sure to take advantage of the conspicuous lane positioning techniques described later in this guide.

trafficlightsatnight

BikeWalk NC Feedback on NCDOT’s H232 Study Report

BikeWalk NC submitted the following feedback to NCDOT on December 29, 2015 in response to NCDOT’s draft report on the H232 study. The feedback document was accompanied by a cover letter that can be read here.

BikeWalk NC Feedback on NCDOT’s H232 Study Report

12/29/2015

Abstract

BikeWalk NC is greatly concerned by multiple NCDOT recommendations in the H 232 Bicycle Safety Laws Study Report that contradict unanimous votes by the Study Committee and will make bicycling in North Carolina more dangerous and more difficult. We oppose NCDOT’s recommendations that

(1) bicyclists be required to operate in the right half of a marked lane, that

(2) municipalities be allowed to require permits for informal bicycling groups passing through their jurisdictions, and that

(3) restrictions be placed on bicyclists riding side-by-side within a single marked travel lane.

We are also concerned that the recommended night cycling requirements are insufficient. BikeWalk NC supports other recommendations in the report, particularly the provision for passing bicyclists in a no-passing zone when conditions make it safe to do so and the requirements for safer passing.

Operating Position in Roadway

BikeWalk NC is gravely concerned by NCDOT’s issue #7 recommendation that a bicyclist operate in the right half of a marked lane, because this conflicts with effective defensive bicycling techniques employed by knowledgeable bicyclists to improve their safety:

Where a cyclist is riding independently or single abreast, the cyclist shall ride in the right half of the right most travel lane with exceptions described in § 20-146 or except when the cyclist is travelling within 15 miles per hour of the posted speed limit.

The H232 Study Committee voted unanimously in recommendation against changing existing state law applicable to bicyclist operating position on the roadway. NCDOT’s recommendation to restrict this positioning to the right half of the lane conflicts with best practices for safe cycling as taught by all of the major adult bicycling education programs throughout North America and Britain, and conflicts with engineering guidance on placement of Shared Lane Markings (aka sharrows) and Bicycles May Use Full Lane markings as discussed in Chapter 14 of the 2013 ITE Traffic Control Devices Handbook. Conditions where a bicyclist’s safety is enhanced by operating in the center or left hand side of a marked travel lane include

  • To deter same-lane passing when the travel lane is too narrow for a bicyclist and a motor vehicle to operate side-by-side safely in the same lane
  • To improve conspicuity, sight lines and maneuvering space when approaching a location where another driver may pull out into the roadway from a side street, driveway or parking space
  • To improve visibility to oncoming drivers preparing to turn left across the path of the bicyclist
  • To stay a safe distance outside of the door zone of on-street parallel parking

NCDOT’s recommended legal restriction on a bicyclist’s ability to choose their preferred operating position within a marked travel lane will discourage safe bicycling practices and promote conflicts between knowledgeable bicyclists and police. Cycling safety experts have strong scientific theories and compelling evidence to support their claim that a centered or leftward lane position can reduce crash rates at intersections and on narrow-laned roads. NCDOT has offered no operational justification or evidence in favor of restricting bicyclists to the right half of a marked lane. BikeWalk NC recommends against changing the existing law and instead encourages NCDOT to promote public education of effective defensive bicycling practices.

Riding Two or More Abreast

BikeWalk NC objects to NCDOT’s issue #2 recommendation that new legal restrictions be placed on how bicyclists may operate side by side within a single marked lane.

NCDOT recommends that the legislature consider adopting language similar to the following: Bicyclists shall not operate more than two abreast in a single marked travel lane on public roadways except when overtaking another bicyclist.

The H232 Study Committee voted unanimously to recommend that no new regulation of riding abreast within a single lane be enacted, and that an educational program be developed and deployed by NCDOT to promote best practices for group cycling. The Committee believed that existing state laws, such as the requirement for any driver to operate within a single marked lane and for slower traffic to operate within the right hand marked lane, are sufficient to regulate group formation.  NCDOT’s recommended law has no operational justification, and will increase friction between police and bicycling groups, who occasionally appear more than two abreast when rotating or when stopping and restarting at intersections.

Informal Group Rides

BikeWalk NC objects to NCDOT’s issue #8 recommendation that municipalities be enabled to require permitting for informal group rides that pass through their jurisdictions:

The General Assembly may consider enabling legislation for local governments to register informal group rides. Any such legislation should apply to groups of more than 30 cyclists riding for recreational purposes, in a continuous formation, and causing significant delay to traffic flow or preventing safe passing. A group ride that routinely creates queues of vehicles waiting to pass on higher speed roadways should adhere to existing bicycle racing laws, acquiring the necessary permits issued by local or state agencies.

No proposal for municipal regulation of group rides was ever presented or discussed at the H232 Study Committee meetings. The committee recommended that NCDOT examine the state level special event permit process to address complaints about excessive road closure times, public communication and other issues that were raised about special events during the Committee meetings. The Committee recommended that educational programs be developed and deployed to address public concerns with informal group rides.

Enabling local regulation of through traffic would pose serious problems for intra-state travel. Travelers would be required to research the local laws of every municipality through which they would travel, instead of relying on the uniformity of state-wide regulations. NCGS § 20-169, Powers of local authorities, places strict limitations on how local authorities may regulate traffic in order to ensure uniformity of statewide traffic laws for normal vehicle operation and to facilitate practical travel through multiple jurisdictions.  Informal group bicycle rides are very popular due to the increased safety, comfort and support they provide to participants. These rides routinely pass through multiple jurisdictions on a single trip. If municipalities were allowed to require local permits for informal bicycling groups, those groups would need to research the ordinances of multiple jurisdictions and obtain multiple permits in order to meet their travel objectives. Such an onerous burden would severely impact and deter bicycling – an effect with conflicts with the state’s adopted Complete Streets Policy.

Before undertaking any drastic change to the road environment or traffic laws, the responsible course of action is to study actual traffic conditions and the potential effects of proposed changes. In its report, NCDOT admits that it has no data to quantify motoring delays related to informal groups and is simply responding to motorist complaints about bicycle traffic:

It is unknown the extent to which group rides without special event permits have prevented safe passing or caused unreasonable traffic delay. […] While the number of crashes and injuries associated with group rides appear to be rare; this issue appears to be the one that creates the most angst among motorists and cyclists. Establishing clearer expectations and informing both motorists and cyclists should help ease the angst.

NCDOT provides no justification for treating congestion delays from high volumes of bicycle traffic differently from that caused by high volumes of motor traffic, and provides no description of how the proposed restrictions on informal group rides would be enforced. What is an unreasonable delay? Would police be required to count bicyclists? If the number exceeds a threshold, who is to blame? Would all of the cyclists in the group be ticketed? The law enforcement officers on the Study Committee testified that group ride size regulations would be difficult and unpopular to enforce.

Participants in informal group rides point out that motorists are usually able to pass them after just a few seconds of waiting for a safe opportunity, and rarely does the delay last more than a minute. BikeWalk NC suggests that the burdensome regulatory approach recommended by NCDOT is highly disproportionate to the minor convenience impacts of group bicycling.

Visibility and Lighting Requirements

BikeWalk NC is concerned that the Study Report recommendations for night visibility do not increase the minimum visibility distance from the rear of the bicycle compared to the existing law. Given the high speed of traffic on many roads that utilitarian bicyclists need to use to reach their destinations, BikeWalk NC recommends that bicyclists operating at night be required to use rear lights visible from 1,000 feet away, equivalent to the standard required of bicyclists in Sweden, and which is easily met by most commercially available bicycle LED tail-lamps.   Using the 200-foot standard in the law is inadequate considering stopping distances and given that most inexpensive ($10 to $20) lights are typically visible for a quarter mile (over 1,000 feet).

Other Provisions

BikeWalk NC supports the other Study Report recommendations, most of which are aligned with the Committee recommendations.

  • How faster-moving vehicles may safely overtake bicycles: The report recommendation to allow drivers to pass bicyclists in no-passing zones when safe, under clearly limited conditions, brings state law into alignment with existing safe passing behavior employed by prudent drivers on narrow rural roads. Most motorists move across a solid centerline to pass bicyclists at safe distance after waiting until sight distances are adequate and no conflicting traffic is present. Motorists recognize that the sight distance required to pass a bicyclist safely is usually far shorter than that required for passing a motor vehicle traveling near the maximum posted speed limit, and that a solid centerline is an unreasonable restriction against passing a bicyclist when it can be done safely.
  • Whether bicyclists should be required to carry a form of identification: BikeWalk NC encourages bicyclists to carry identification as a best practice but strongly supports the report recommendation against requiring ID as this would pose a burden for some cyclists who do not possess official IDs.
  • Options for hand signals for turning: BikeWalk NC supports the recommendation to allow use of the right hand to signal right turns.
  • 2-foot or other passing distance requirements: BikeWalk NC supports the recommendation to increase the minimum distance for passing a bicyclist; the existing two foot distance is inadequate when passing a bicyclist who must maintain balance and is not protected by a safety cage.
  • Use of headphones or texting while cycling: BikeWalk NC agrees with the report recommendation.
  • Aggressive driving, harassment, and distracted driving laws: BikeWalk NC agrees with the report recommendation.
  • Vulnerable road user protection: BikeWalk NC supports the report recommendation to extend the legal protection of motorcyclists to bicyclists.
  • Formal group event permitting and regulations: BikeWalk NC agrees with the report recommendation to study and improve how special event road closures are implemented.

Defanging the Automobile

Sensor-assisted cars that can avoid injuring pedestrians and cyclists are here, and will become the standard in a few years

by Steven Goodridge

“A robot may not injure a human being or, through inaction, allow a human being to come to harm.” 

– Isaac Asimov’s First Law of Robotics

An interesting thing happened on the way to the self-driving vehicle: Smart collision prevention technology such as automatic emergency braking became practical for regular cars. After premiering in high-end vehicles with adaptive cruise control and lane departure warning systems, radar and camera systems have become commodity products now available in about a quarter of 2015 model year cars. As volumes have increased and the technology refined with custom silicon, prices have plummeted, with the typical cost of a smart camera or radar sensor now around $150 for an automaker to add to a car. And increasingly, the use of the such smart-car sensors has become focused on preventing collisions and saving lives, including those of pedestrians and bicyclists, who make up about half of fatal road crash victims worldwide.

Raising the Bar

Beginning in January 2016, any automaker hoping to earn the Euro NCAP 5-star safety rating for their product will be required to equip the car with automatic emergency braking capabilities that include pedestrian detection.  The  National Highway Transportation Safety Agency (NHTSA) recently announced a similar plan for its own five-star safety rating, as has the Insurance Institute for Highway Safety (IIHS) . Volvo, not surprisingly, now includes its pedestrian and bicyclist detection system with full-automatic braking as standard equipment on all of their new cars.  Lotta Jakobsson, a Senior Technical Specialist at Volvo, describes the motivation for the technology: “Statistics show that about 90 percent of all accidents are caused by distracted drivers. Since City Safety remains alert even if the driver is distracted or tired, it helps to bring collision figures down considerably.” Although driver training and vigorous enforcement of traffic laws are essential to preventing crashes, mistakes will always be made by human drivers, bicyclists and pedestrians. Automated systems can reduce the human cost of those errors. For instance, a March 2015 analysis of car-bike crashes conducted by IIHS concluded that equipping traditional cars with automatic crash avoidance systems programmed to address the five most common car-bike crash types could prevent or mitigate up to 47 percent of car-bike crashes.

Consumer Interest

Do Americans really want R2-D2 riding along as back-seat driver? According to an April 2015 study by the Boston Consulting Group, drivers will demand automatic crash avoidance features to get lower insurance premiums.  The insurance industry has measured reduced crashes and claim costs for cars with the technology. An IIHS Highway Loss Data Institute (HLDI) study revealed that Honda Accord models featuring a new forward collision warning system reduced claims for injuries to occupants of the equipped vehicles by 27 percent and claims for injuries to other road users by 40 percent. Insurers are now passing a portion of these savings on as reduced premiums for such cars. As Americans replace their aging vehicles and automatic collision systems become standard features, the majority of registered cars on US roads are likely to be equipped with the technology sometime between 2025 and 2030.

Entry Level Technology

The first bicyclist-and-pedestrian-friendly crash avoidance features to reach the car market are forward collision warning (FCW) systems and automatic emergency braking (AEB) systems. FCW systems detect when the driver is on a collision course with a motor vehicle, bicycle, or pedestrian ahead and alert the driver with a visible and audible warning if they have not begun braking in time to avoid a potential crash. AEB systems go one step further by applying the brakes to slow or stop the car and thereby prevent or mitigate the collision if the driver fails to brake effectively, or at all. Most current FCW and AEB systems combine a forward-looking radar unit in the grill and a camera behind the windshield to determine the range and position of objects ahead and identify which ones require a response. These are the same or similar sensors as those used for adaptive cruise control and lane departure warning. First generation FCW and AEB systems should be well suited to prevent car-bike rear-ending crashes, where the car approaches a bicyclist from behind traveling in the same lane ahead in the same direction. Junction and crossing type collisions involving pedestrians and cyclists coming from the sides of the vehicle’s path require wider angle sensing and pose more complex recognition challenges.

Automotive Radar

Radar sensors operate regardless of lighting conditions and in practically all weather except dense fog. Electronically steered radar units operating at 77 GHz provide detection and ranging of multiple vehicles and other objects simultaneously at ranges of up to 200 meters within a narrow (15-20 degrees) field of view. Such systems can detect pedestrians, bicyclists and motorcycle users in the roadway at ranges of up to 40-100 meters depending on their size. For shorter range sensing over a wide (120 degree) angle at high angular resolution, 24 GHz radar has been used, but only on a temporary basis due to evolving regulation of this frequency band. This wider angle is particularly important for detection and recognition of pedestrians and bicyclists who may be crossing or about to cross in front of the vehicle in urban situations. A disadvantage of 77 GHz radars for pedestrian recognition and tracking is their limited angular resolution, resulting from the limited bandwidth allowed by the FCC for those frequencies. One strategy to increase angular resolution for pedestrian sensing is to use a more sophisticated ultra-wide-band radar system operating at 79 GHz, which will allow much wider bandwidth for automotive radar.  The FCC is currently in the process of opening up the 79 GHz band for automotive radar, as has been already done in Europe. The solution employed by US car manufacturers today, however, is to complement limited-resolution radar with camera-based and/or LIDAR sensing.

Computer Vision

Camera systems provide high resolution sensing for shape recognition and position estimation.  A variety of algorithms exist for detection and recognition of pedestrians in video. Some collision prevention systems depend entirely on monocular video analysis for detection of hazards; others, such as Subaru’s EyeSight system, use stereo vision for range perception without radar.  Visible light cameras can be affected easily by darkness, glare and weather, making them less robust than radar. Infrared cameras address some of these limitations, but are more expensive than visible light cameras. Sensor fusion of video and radar data can leverage the complementary strengths of each mode for more robust operation.

LIDAR

The ultimate sensor for automated situational awareness may be laser radar, aka LIDAR. The sweeping beam of LIDAR provides a very high resolution range image, which is favored by developers of fully autonomous cars for its value in self-localization and object tracking. LIDAR is its own light source, operating under all types of ambient outdoor illumination, but has a shorter range than radar. Increasing the power and range of LIDAR usually requires a bulkier form factor, such as the large cannisters seen atop many prototype autonomous cars. Inconspicuously packaged short-range LIDAR is being used by a number of car companies (including Volvo in their City Safety product) to complement radar and camera sensing for improved resolution of range data.

Sonar

At very short ranges, ultrasonic sensors outperform other technologies. Sonar sensors have been used in back-up safety systems on trucks for decades, and are now used in the parking-assist systems on many new cars. These sensors have the potential to prevent thousands of tragic backover collisions involving children.

360degreesensing

Radar, vision and sonar sensors for 360 degree awareness. [Image provided courtesy of Analog Devices]

360 Degree Awareness

Comprehensive crash avoidance technology will require 360 degree sensing around the vehicle. Automakers envision a combination of multiple radar, sonar, camera and/or LIDAR units to provide the type of traffic detection required in each direction. These include close-range sonar for parking assist and backover prevention, medium range radar for blind spot sensing, lane change and cross traffic detection, video for lane departure warning and object recognition, and long range radar for same and opposite direction vehicle detection. As hardware costs continue to decline with electronics integration and simplified packaging, the number of sensors that appear on new cars will quickly multiply in the next few years.

Limitations

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Multiple threat collision mode involving sight obstruction. [FWHA image]

Despite distraction-free, continuous operation, even the best modern vehicle sensors cannot prevent all crashes. Many crashes involving bicyclists and pedestrians involve occlusion of sight lines between the motor vehicle and the other party until just before collision. One example is the multiple-threat pedestrian crash, where the view between a motor vehicle and a pedestrian crossing the roadway is blocked by another vehicle that has stopped in the adjacent lane. A similar situation exists when traffic screens the view between a left turning driver and a thru bicyclist.  Existing left turn assist systems cannot see through cars and operate only at low speed. Research into improved left turn assist and occluded view collision prevention systems has focused on using vehicle-to-vehicle (V2V) and infrastructure-to-vehicle communication to supplement the sensors on a single vehicle. This strategy provides measurement of pedestrian and bicyclist activity by sensors at one or more locations and transmitting it to multiple vehicles that may encounter movement conflicts. However, due to a variety of liability, privacy, security and safety challenges,  initial V2V communications deployment is still a few years away.

Unlike human beings, modern vehicle sensors cannot infer the intent of human beings near the roadway or predict dangerous behavior. Existing technology cannot tell the difference between a waiting adult and a confused person or child who might dart suddenly into traffic; just discriminating between humans, animals, and mailboxes can be difficult enough. Crash avoidance systems on the market today cannot compensate for reckless or drunk driving, or persistent distracted driving. Although technology is in development to deter and detect such behaviors, there is less consumer enthusiasm and market demand for technology that watches drivers directly than for technology that looks outside the car.

The current crop of forward collision warning and automatic braking systems are optimized for relatively low vehicle speeds where sensing and stopping distances can be kept short. This may work well enough in European nations where streets through most built-up areas feature speed limits of 30 mph or even just 20 mph. But in the US, most US pedestrian and bicyclist fatalities occur on roads posted 40 mph or higher. Much of our urbanization developed around high speed thoroughfares, so pedestrians and bicyclists commonly travel upon and across roads with speed limits of 35 to 55 mph. This requires reliable detection and tracking of bicyclists and pedestrians at longer distances, where the resolution of today’s narrowband automotive radar systems can become a limiting factor. Moving forward, it will be critical for regulatory authorities such as NHTSA to develop meaningful performance metrics for bicycle and pedestrian detection by collision avoidance systems operated under realistic US thoroughfare conditions.

The limitations of automated crash avoidance systems mean that all of the proven engineering, education and enforcement safety measures used to support pedestrian and bicyclist safety (such as lower speeds) will continue to be important. Street environments that improve human drivers’ ability to see and yield to pedestrians and cyclists will also improve the reliability of automated systems. Engineering that rewards safe pedestrian and bicyclist behavior by making it convenient and easy will continue to reduce hazardous conflicts as automation increases.

Risk Compensation

One concern that has been expressed about automated crash avoidance systems is the possibility that drivers will compensate by being less vigilant, relying on the technology to save them during distractions. Efficacy studies performed to date show real reductions in crash rates, but more data will be required to rule out the possibility of risk compensation. The worst case scenario would be for drivers’ risk compensation to cancel out the technology’s reduction in car-car crash risk, but for the technology to fail to detect bicycles and pedestrians reliably, resulting in an increase in car-bike and car-pedestrian crashes.

Alternatively, if smart car technology does reduce the crash risk to pedestrians and bicyclists, and these road users become more confident and travel more, this would be a very good thing. Traffic safety concerns are a common reason people give when asked what factors limit their bicycling and walking. The health and societal benefits of increasing walking and cycling generally outweigh the risks today, and this will be only more true in the future. One of the most commonly cited fears given by potential utility bicyclists – the fear being struck from behind by a careless, drunk or drowsy driver – depicts a relatively uncommon crash type in urban areas, but is one of the easiest types of collision that can be prevented by automatic braking systems. Elimination of this risk could make many bicyclists to feel more empowered on normal streets, and shift the focus of bicycle traffic safety to the more common intersection conflicts. And if parents knew that they could count on motor traffic to stop and yield at crosswalks, stop signs and red lights, rather than just barreling through them, many more would allow their children to walk independently to school and other destinations. Vehicle automation may be a limited but critical part of a holistic approach to improving the walkability and bikeability of our communities.

Next Steps

As the NHTSA moves ahead with its AEB recommendations, it will be important for pedestrians, bicyclists, and related stakeholders and advocacy organizations to give the government and car manufacturers a clear message that approved AEB systems must detect pedestrians and bicyclists reliably under road conditions that are realistic in the USA.  Similar attention to this issue is needed at IIHS. While pedestrian and bicyclist detection performance in AEB systems has been a key interest in Europe and Asia, it does not yet appear to be on American institutions’ radar.

About the Author

Steven Goodridge is a board member of BikeWalk NC and holds a Ph.D. and MS in electrical engineering from NC State University, where he studied autonomous robotic vehicle systems, computer vision and sensor fusion. Dr. Goodridge enjoys teaching traffic bicycling classes and commuting to work by bike in Cary.

Important NC Traffic Laws Applicable to Bicyclists

Like other states, North Carolina traffic laws treat bicycles as vehicles and treat bicyclists as drivers of vehicles. This article lists some of the most important traffic laws applicable to bicycle operation in North Carolina. For more detail and a list of all state traffic laws, consult the resources listed at the bottom of this article.

NC Bicycle Laws on Vimeo.

Bicyclists are Drivers of Vehicles

§ 20-4.01(49) Vehicle. – …for the purposes of this Chapter bicycles shall be deemed vehicles and every rider of a bicycle upon a highway shall be subject to the provisions of this Chapter applicable to the driver of a vehicle except those which by their nature can have no application.

As drivers of vehicles, bicyclists are allowed to travel on all public roadways except fully controlled access highways (freeways) such as interstates. NCAC 19A.2E.0409 OPERATING NONMOTORIZED VEHICLES: It is unlawful for any person to ride any animal, or to operate a bicycle or horse drawn wagon or any nonmotorized vehicle or moped on any interstate or other fully controlled access highway.

Bicycles are not Motor Vehicles

§ 20-4.01(23) Motor Vehicle. – Every vehicle which is self-propelled ….

Night Equipment

§ 20-129.  Required lighting equipment of vehicles. (e) Lamps on Bicycles. – Every bicycle shall be equipped with a reflex mirror on the rear and both of the following when operated at night on any public street, public vehicular area, or public greenway:
(1) A lighted lamp on the front thereof, visible under normal atmospheric conditions from a distance of at least 300 feet in front of such bicycle.
(2) A lamp on the rear, exhibiting a red light visible under like conditions from a distance of at least 300 feet to the rear of such bicycle, or the operator must wear clothing or a vest that is bright and visible from a distance of at least 300 feet to the rear of the bicycle.

First Come, First Served: Duty to Limit Speed and Slow for Slower Traffic Ahead

§ 20-141.  Speed restrictions. (a) No person shall drive a vehicle on a highway or in a public vehicular area at a speed greater than is reasonable and prudent under the conditions then existing. … (m) The fact that the speed of a vehicle is lower than the foregoing limits shall not relieve the operator of a vehicle from the duty to decrease speed as may be necessary to avoid colliding with any person, vehicle or other conveyance on or entering the highway, and to avoid injury to any person or property. § 20-140.  Reckless driving. (b) Any person who drives any vehicle upon a highway or any public vehicular area without due caution and circumspection and at a speed or in a manner so as to endanger or be likely to endanger any person or property shall be guilty of reckless driving.

Drive on Right Side of the Road

§ 20-146.  Drive on right side of highway; exceptions. (a) Upon all highways of sufficient width a vehicle shall be driven upon the right half of the highway except as follows: (1) When overtaking and passing another vehicle proceeding in the same direction under the rules governing such movement; (2) When an obstruction exists making it necessary to drive to the left of the center of the highway; provided, any person so doing shall yield the right-of-way to all vehicles traveling in the proper direction upon the unobstructed portion of the highway within such distance as to constitute an immediate hazard; (3) Upon a highway divided into three marked lanes for traffic under the rules applicable thereon; or (4) Upon a highway designated and signposted for one-way traffic.

Stop/Yield Before Entering a More Important Roadway

§ 20-158.  Vehicle control signs and signals. (b) Control of Vehicles at Intersections. – (1) When a stop sign has been erected or installed at an intersection, it shall be unlawful for the driver of any vehicle to fail to stop in obedience thereto and yield the right-of-way to vehicles operating on the designated main-traveled or through highway. When stop signs have been erected at three or more entrances to an intersection, the driver, after stopping in obedience thereto, may proceed with caution. (2) a. When a traffic signal is emitting a steady red circular light controlling traffic approaching an intersection, an approaching vehicle facing the red light shall come to a stop and shall not enter the intersection. After coming to a complete stop and unless prohibited by an appropriate sign, that approaching vehicle may make a right turn. b. Any vehicle that turns right under this subdivision shall yield the right-of-way to: 1. Other traffic and pedestrians using the intersection; and 2. Pedestrians who are moving towards the intersection, who are in reasonably close proximity to the intersection, and who are preparing to cross in front of the traffic that is required to stop at the red light.

Yield before Moving Laterally

§ 20-146.  (d) (1) A vehicle shall be driven as nearly as practicable entirely within a single lane and shall not be moved from such lane until the driver has first ascertained that such movement can be made with safety.

Destination Positioning at Intersections

§ 20-153.  Turning at intersections. (a) Right Turns. – Both the approach for a right turn and a right turn shall be made as close as practicable to the right-hand curb or edge of the roadway. (b) Left Turns. – The driver of a vehicle intending to turn left at any intersection shall approach the intersection in the extreme left-hand lane lawfully available to traffic moving in the direction of travel of that vehicle, and, after entering the intersection, the left turn shall be made so as to leave the intersection in a lane lawfully available to traffic moving in the direction upon the roadway being entered.

Speed Positioning: Overtaking on Left

§ 20-149.  Overtaking a vehicle. (a) The driver of any such vehicle overtaking another vehicle proceeding in the same direction shall pass at least two feet to the left thereof, and shall not again drive to the right side of the highway until safely clear of such overtaken vehicle. This subsection shall not apply when the overtaking and passing is done pursuant to the provisions of G.S. 20-150.1.

Speed Positioning: Limitations on Overtaking on Right

Bicyclists may not overtake other traffic on the right except when in a separate marked travel lane. § 20-150.1.  When passing on the right is permitted. The driver of a vehicle may overtake and pass upon the right of another vehicle only under the following conditions: (1) When the vehicle overtaken is in a lane designated for left turns; (2) Upon a street or highway with unobstructed pavement of sufficient width which have been marked for two or more lanes of moving vehicles in each direction and are not occupied by parked vehicles; (3) Upon a one-way street, or upon a highway on which traffic is restricted to one direction of movement when such street or highway is free from obstructions and is of sufficient width and is marked for two or more lanes of moving vehicles which are not occupied by parked vehicles; (4)        When driving in a lane designating a right turn on a red traffic signal light. (1953, c. 679.)

Speed Positioning: Slower Traffic Use Right Thru Lane

 20-146.  Drive on right side of highway; exceptions. (b) Upon all highways any vehicle proceeding at less than the legal maximum speed limit shall be driven in the right-hand lane then available for thru traffic, or as close as practicable to the right-hand curb or edge of the highway, except when overtaking and passing another vehicle proceeding in the same direction or when preparing for a left turn.

BMUFL

R4-11 sign (MUTCD)

A bicyclist may use a full marked lane. “Bicyclists usually ride on the right side of the lane, but are entitled to use the full lane…. Drivers wishing to pass a bicyclist may do so only when there is abundant clearance and no oncoming traffic is in the opposing lane. When passing a bicyclist, always remember the bicyclist is entitled to use of the full lane.”   – North Carolina Driver’s Handbook, p.95.  

Non-Motorized Vehicles Exempt from Impeding Traffic

§ 20-141. (h) No person shall operate a motor vehicle on the highway at such a slow speed as to impede the normal and reasonable movement of traffic except when reduced speed is necessary for safe operation or in compliance with law; provided, this provision shall not apply to farm tractors and other motor vehicles operating at reasonable speeds for the type and nature of such vehicles.

Impaired Driving Law Applicable to Bicyclists

§ 20-138.1.  Impaired driving. (a) Offense. – A person commits the offense of impaired driving if he drives any vehicle upon any highway, any street, or any public vehicular area within this State: (1) While under the influence of an impairing substance; or (2) After having consumed sufficient alcohol that he has, at any relevant time after the driving, an alcohol concentration of 0.08 or more. The results of a chemical analysis shall be deemed sufficient evidence to prove a person’s alcohol concentration; or (3) With any amount of a Schedule I controlled substance, as listed in G.S. 90-89, or its metabolites in his blood or urine.

Children under 16 Must Wear Helmets

§ 20-171.9.  Requirements for helmet and restraining seat use. With regard to any bicycle used on a public roadway, public bicycle path, or other public right-of-way: (a) It shall be unlawful for any parent or legal guardian of a person below the age of 16 to knowingly permit that person to operate or be a passenger on a bicycle unless at all times when the person is so engaged he or she wears a protective bicycle helmet of good fit fastened securely upon the head with the straps of the helmet. (b) It shall be unlawful for any parent or legal guardian of a person below the age of 16 to knowingly permit that person to be a passenger on a bicycle unless all of the following conditions are met: (1) The person is able to maintain an erect, seated position on the bicycle. (2) Except as provided in subdivision (3) of this subsection, the person is properly seated alone on a saddle seat (as on a tandem bicycle). (3) With respect to any person who weighs less than 40 pounds, or is less than 40 inches in height, the person can be and is properly seated in and adequately secured to a restraining seat.

For more information:
RIDE-GUIDE

Bike Law lawyer Ann Groninger’s guide to North Carolina bicycle laws

Ride Guide – Detailed discussion of NC Bicycle Laws by NC Lawyer and Bike Law founder Ann Groninger

North Carolina Vehicle Code (NCGS Chapter 20)

NC Driver Handbook

Education Resources for Police

Bicycling at Night

For good reason, North Carolina state law (§ 20-129.e) requires bicycles operated at night to be equipped with a white headlamp in front and rear reflector plus red lamp or reflective garment in back. Never ride at night without a headlamp and a rear lamp. Although most bicycles are sold with small “toy” reflectors, these are terribly inadequate for safe night cycling. The car-bike collision rate is several times higher at night than during daylight, but the vast majority of these crashes involve cyclists operating without proper nighttime equipment and can be easily prevented. Proper equipment makes cyclists visible to other road users and can make cycling at night much safer than statistics suggest that it is.

Proper bicycle lighting is important for two reasons:

  1. It makes you visible and predictable to other road users
  2. It can help you see well enough to avoid hazards and navigate your way

Being Visible and Predictable

Many cyclists ride in urban environments where they feel that they can see well enough to navigate, so they don’t bother with headlamps. This can be very dangerous, because without a headlamp other drivers often do not see them, even under street lamps. Reflectors can provide good visibility for overtaking traffic under some circumstances, but most dangers of car-bike collisions come from the front or side of the cyclist. The headlamp beams of vehicles on intersecting paths with cyclists often do not shine upon the reflectors of a bicycle until it is too late for the motorist to yield right of way or avoid collision. The figure below shows the positions of two vehicles that might be about to drive out or turn across the cyclist’s path

nightcycling_img20

Vehicle headlamps often do not illuminate the cyclist’s reflectors, creating a danger at intersections.

The photos below show the difference in visibility of a cyclist with and without a front headlamp.

nightcycling2
An approaching cyclist in the roadway under a street lamp, with no front light.

nightcycling3

A cyclist approaching in the same position as above, this time with a headlamp on the bicycle plus a helmet lamp.

Bicycle headlamps should emit a steady white (or nearly white) light because this indicates the direction that the vehicle is traveling. Most vehicles, including aircraft and boats, exploit a color convention to indicate orientation or direction of travel. For road vehicles, red lights belong in back, amber lights on the side, and white lights in front. The fact that reverse-gear lights of a motor vehicle are white provides an important cue as to what the motorist is about to do. It’s important for cyclists to comply with this convention in order for other road users to predict their actions. For instance, using a red lamp on the front of a bicycle is likely to cause opposite-direction divers to underestimate the closing speed between vehicles because they will expect the red-lighted object to be either stationary or moving in the same direction.

A red rear lamp or reflector makes a bicycle visible to overtaking traffic. It’s important to make this reflector or lamp large enough and bright enough to be seen by motorists at enough distance to slow or stop in time when traveling at high speeds. Color is generally less important on the rear of the vehicle, since overtaking motorists will not be any less cautious when viewing another color, but red is the convention and is a universally understood warning indicator. A variety of red LED (Light Emitting Diode) tail lamps available for bicycles; these lamps are visible at longer distances and a wider angles than are most reflectors, and don’t depend on vehicle headlights to be effective.

Note that side reflectors don’t hurt, but they are rarely of much use because if a vehicle’s headlamps are shining on them, you will either be riding ahead and out of the way before the vehicle arrives or it is already too late for the driver to avoid you. Pedal reflectors are more useful; some drivers report that pedal reflectors are even more conspicuous than tail lamps when approaching a bicyclist from behind. Reflective dots on shoe heels are an alternative for clipless pedal users.

Seeing What’s Ahead

The amount of light your headlamp needs to shine on the roadway in order to see your way depends on where and how fast you ride. A cyclist riding at high speed on a dark rural road needs a long, relatively narrow beam of light to see surface conditions and obstacles far enough ahead. A mountain biker riding over challenging off-road terrain needs a wide, bright beam to find suitable paths over obstacles and around turns. By contrast, an urban cyclist operating under street lamps may require just enough beam strength to allow navigation of the occasional dark stretch at reduced speed.

The faster you ride, the longer your effective headlamp beam needs to be; if you double your speed, you need to see twice as far. Note that since the perceived power of reflected light decreases in proportion to the square of distance from the lamp, doubling the range for a given reflection power requires four times as much light power from the lamp.  The light provided by a bicycle headlamp may be focused into a narrow beam for maximum range, or may be spread out for better peripheral vision. A low powered lamp can be focused into a beam suitable for high speed cycling on the darkest roads, but such a pattern will not give much illumination of turns. Any headlamp, even the cheapest clip-on battery kind, is much safer than none at all – you just need to ride slower to compensate for reduced range.

On totally dark roads, our eyes adapt to the darkness and allow us to see surprisingly well with a low-power headlamp. However, street lamps and the headlamps of oncoming cars can inhibit or reverse the adaptation of our eyes. This makes cycling on partially-lit roads or with oncoming traffic on rural roads more challenging with low-power headlamps. It’s a good idea to use the most powerful headlamp available for your cycling needs and your price range.

Special Hazards to See

Remember that motor vehicle traffic isn’t the only hazard at night. Don’t be surprised to find animals, unlit pedestrians dressed in black, and unlit wrong-way cyclists in your path at night. Look for them carefully, and give them wide berth when you see them. Also remember that it’s harder to see potholes and gravel. Also, wet road surfaces do not reflect as much light as dry roads, making driving lights (head and frame mounted white lights) less effective.

Increased Hazards from Motorists

On average, the percentage of highway users who are impaired by fatigue, poor night vision and alcohol increases at night. Drunk, drowsy, and severely distracted drivers are the greatest threat to lawfully operating cyclists at any time of day. Fortunately, the total number of motorists on the roads usually decreases at night. Many experienced night cyclists who use proper lighting report that overtaking motorists give them wider berth after dark. With reduced traffic and strong lights, it is arguable that the properly equipped night cyclist may actually be more visible and easier for motorists to avoid than the daytime cyclist.

Riding into the Sun

One situation which cannot be helped much by night equipment is poor cyclist visibility when riding directly into sunrise or sunset. Motorists are often blinded to the point that they can barely see more than the outlines of motor vehicles ahead of them. Under such conditions, the law requires drivers to slow down to a speed at which they will be able to respond safely, yet in too many cases they continue to drive at full speed. If possible, a cyclist may wait for the sun to set (you have your lights, right?) or to rise higher before riding. If you do ride into the sun, leave drivers a longer buffer of response time and distance when entering the lane in front of them.

Choosing the Right Equipment

Headlamps

A variety of bicycle headlamps are available depending on the user’s preference for range, light output, mounting style, and cost. Helmet mounted lights put the light where you’re looking. Bike mounted lights put the light near where your bike is going to be very soon. For maximum effectiveness, you can use both. Note that it’s also good to have a back-up light source or spare batteries.

The cheapest, shortest-range lights suitable for emergencies or occasional urban use are low-wattage clip-on lamps powered by disposable batteries stored inside the lamp housing. These lamps can get you home safely when you’re out after dark, and are good as a back-up, but most don’t have enough light output for high speed cycling on dark roads, they usually have limited range, and most of them eat batteries. Recent advancements in LED-based headlamps have greatly improved the range and light power of inexpensive battery-powered clip-on lamps.

nightcycling4

LED headlamps powered by AA batteries are now available in a variety of light powers and run times.

Rechargeable battery-powered lighting systems provide the highest light output (starting at around 250 lumens; most good ones are now well above 400 lumens), making them especially popular for mountain biking, and can offer operating times of over two hours between charges. Some even have fuel gauges and multiple power settings so you can control your range. The high power availability allows wide beam width which also maximizes visibility to other road users. Recent advances in battery and lamp technology provide increased power efficiency, lower battery weight, and easier charging, than previous battery-powered headlamp systems. However, these lamp systems usually cost over $50, often well over $100.

nightcycling5

This NiteRider LED headlamp with an internal Li-Ion rechargeable battery provides higher light lumens than disposable-battery lamps.

For unlimited range without the worry of battery maintenance, generators are the ideal choice. Many randonneurs swear by them, since their rides can exceed the operating time of a single battery lamp. Generators may be built into the front hub or attach to the tire. Early-generation generators would not provide any light with the bicycle stopped, would glow dimly at low speed, and could potentially burn out the lamp at high speed. Some modern generator systems use smart electronics to regulate power production such that the lamp is bright even at slow cycling speeds, and ensure there is no danger of burnout at high speeds. Some are even combined with power storage to provide illumination when stopped; the power storage recharges while the cyclist is moving. Generator powered lights reduce your speed capability somewhat because of the extra drag, which may be 10% of your pedaling effort. The most attractive and convenient generators, such as the Shimano DH-3N70 and the Schmidt Dyno Hub, are built into the front wheel hub. Bottle generators, such as the Dynosys LightSpin, rub against the tire.

Front strobes or flashers may also add to the cyclist’s conspicuity. However, these should not be used as a substitute for a normal headlamp.

Rear Reflectors

At close distance, when conditions are right, reflectors can be as visible as rear lamps – but conditions are not always right. Bicycle and automotive reflectors use the cube-corner reflection principle to reflect light back along the same path from which it came. This means that the observer’s eye must be very close to the light source – less than a two degree arc, in fact – to see a strong reflection. If the driver’s side headlamp is not turned on or working, the reflector may not be visible to the driver. The reflector must also be close to perpendicular to the observation angle.

Most bicycles come with small toy reflectors required by the Consumer Products Safety Commission (CPSC). These reflectors are too small to provide adequate visibility under many realistic road conditions, such as high-speed thoroughfares. A typical CPSC reflector provides only 1.7 square inches of directly exposed surface area and 1 square inch of surface angled to one side under optimum viewing conditions. The cyclist is better off replacing this rear reflector with a larger one from an automotive store. A 3? diameter round automotive reflector provides 7 square inches of reflector area. An oblong “trailer” reflector provides six square inches.

Note that an amber reflector is 2.5 times as bright as a red reflector under the same headlight illumination. By law, a red reflector is required, but adding an amber reflector to the red one is a good idea. With this combination, you’ll be over ten times brighter than with just one toy CPSC reflector.

Reflectors are very sensitive to mounting location and orientation. Reflectors on the frame should be mounted low to reflect the lights of other vehicles sooner. The face of the reflector should be perpendicular to the ground. If the rear reflector is where it may be sprayed by mud from the tire, clean it often.

Tail Lamps

Inexpensive tail lamps, typically employing red, energy-efficient light emitting diodes (LEDs), don’t rely on a motorist’s headlamps to be visible, are visible from farther away, and can be seen clearly from the side as well.

 

nightcycling6

The Planet Bike Superflash Turbo is a 1 Watt LED tail lamp that is daylight visible and will get you noticed at night from a mile away.

These lamps will last many hours on a pair of disposable batteries. However, they often glow dimly long before they fail; it’s important to inspect them before each ride and change the batteries regularly. Above all, use a reflector in addition to the tail lamp so you have a backup. Note that many of the clamp-on mounts for tail lamps and reflectors are easily knocked out of alignment. Be sure to inspect them often, and consider using more than one retro-reflective device on separate mounts in case one gets misaligned without you noticing it. (Once, after hitting a pothole, the author discovered that the shock had caused the cover of his VistaLite tail lamp to pop off and dump its batteries with it. Were it not for a secondary reflector, the bicycle would have had no rear-facing visibility equipment for the remainder of the trip. A band of electrical tape around the perimeter of the lens can keep this from happening and also seal out water.)

Steady versus Pulsating versus Flash

There is some controversy over whether pulsating tail lamps are better than steady tail lamps. A rapid pulse is better than a slow flash, because it is easier to track visually. (Remember the difficulty of catching fireflies between flashes?) The rapid pulse also grabs attention more readily at long distances than does a solid lamp. Proponents of steady lamps say steady lamps are just as visible at short distances, which they say is what counts, that steady lamps are potentially less annoying or distracting, and that there is little use in looking different from other traffic.  Proponents of flashing lamps believe that it is useful to alert motorists to the presence of a special road user (a bicyclist) farther ahead so the motorist can better prepare in advance to overtake with caution.  Also, flashing lamps use much less average power to achieve the same maximum instantaneous brightness.

Reflective Clothing

Lights are essential for visibility under all conditions. However, retro-reflective clothing may help approaching drivers estimate your size and distance more easily and accurately than can just a single lamp or reflector. Ankle or pedal reflectors move and attract attention. Reflective material on a jacket or glove also help you convey hand signals at night. Remember that retro-reflective clothing supplements, but never replaces, good lights and bike-mounted reflectors.