Education

Jul 11 2015

BikeWalk NC Priority Recommendations for Bike Law Study

BikeWalk NC has developed the following priority recommendations for the Study/Update on Bicycle Safety Laws to be conducted by NCDOT according to HB 232. These summary recommendations can be downloaded as a printer-friendly .pdf file. A detailed support document for these recommendations, discussing existing law and best bicycling practices, is also provided in .pdf format.

BikeWalk NC Recommendations on North Carolina Traffic Laws

7/20/2015

Abstract

North Carolina’s existing traffic laws are among the best in the nation in terms of their alignment with best bicycling practices (see attachment) and their support for bicyclists’ travel objectives. BikeWalk NC supports better public education and law enforcement to promote public understanding of and compliance with best operating practices for all vehicles. BikeWalk NC opposes law changes that would interfere with the exercise of defensive bicycle driving techniques and put such bicyclists at risk of citations. This paper presents BikeWalk NC’s recommendations for minor changes to state traffic laws to enhance support for best bicycling practices and safe passing maneuvers by motorists, and specifies some of the existing laws that we recommend be left unchanged.

1. Relax the Solid Centerline Rule

Recommendation: Modify § 20-150 (e) to allow drivers to cross a solid centerline when passing a slow moving bicyclist only when safe and done in compliance with restrictions § 20-150 (a), (b), (c), and (d).

Justification: Most rural roads are too narrow for motorists to pass bicyclists safely within the bicyclist’s lane; unsafe same-lane passing is the leading cause of same-direction car/bike collisions in daylight. Prudent motorists routinely cross solid centerlines to pass bicyclists safely where there is clear sight distance to do this in compliance with § 20-150 (a), (b), (c), and (d). Sight distance required for passing a bicyclist safely is usually much shorter than that required for passing a motor vehicle, but dashed centerline placement policies assume passing of motor vehicles traveling just under the maximum posted limit. Strict enforcement of the solid centerline passing prohibition is grossly misaligned with routine passing of bicyclists and puts police in conflict with prudent motorists. Passing restrictions in § 20-150 (a), (b), (c), and (d) must continue to be enforced and public education about safe passing is recommended. Several other states allow crossing a solid centerline to pass bicyclists. See in-depth article at http://iamtraffic.org/engineering/crossing-double-yellow-line/

2. Add a Rear Lamp Requirement

Recommendation: Modify § 20-129 (e) to require bicyclists to use a red rear lamp, either blinking or steady, in addition to the already-required white front headlamp, when bicycling at night.

Justification: Over half of fatal car-bike collisions occur in darkness, mostly involving unlighted bicyclists. Typical rear bicycle reflectors provide marginal or insufficient visibility in common nighttime traffic conditions such as high speed roads and where vehicles are turning. Red LED bicycle tail lamps provide vastly superior rear visibility, and are generally less expensive than bicycle headlamps, which will continue to be required.

3. Allow use of the Right Arm for Right Hand Signals

Recommendation: Modify § 20-154 (b) to allow optional use of the right arm to signal a right turn or other rightward movement. This would mirror the existing left hand signal, i.e.

Left turn – hand and arm horizontal, forefinger pointing.

Right turn – hand and arm pointed upward. Optionally, if operating a bicycle or motor-driven cycle, right hand and arm horizontal, forefinger pointing.

Justification: The right arm is more visible than the left arm to other road users who are most affected by a right turn or rightward movement, i.e. users to the right of the bicyclist. A bicyclist must turn their head and torso to look backward on their right side before moving rightward safely on the road; a left-armed hand signal interferes with this body movement, but a right-armed hand signal assists it. About half of US states allow bicyclists to use the right arm for signaling rightward movements.

4. Penalize Careless Driving

Recommendation: Complement the Class 2 misdemeanor of reckless driving (§ 20-140) with a lesser offense of driving without due care and attention, aka careless driving. This would apply to careless and/or inattentive driving of any vehicle (including a bicycle) in a manner that endangers or would be likely to endanger any person or property, but does not meet the definition of reckless driving. Assign elevated penalties for injuring or killing other persons while engaged in careless driving.

Justification: Inattentive and careless driving is a major safety concern for all road users, by some analyses contributing to the majority of vehicle crashes. However, the decision to act inattentively or carelessly on the roadway is rarely penalized, even when it directly results in a crash. Police or courts may believe that some careless behavior does not rise to the level of “willful or wanton disregard of the rights or safety of others” per the reckless driving statute or that they may be unable to prove intent. Several states such as Pennsylvania and Oregon define careless driving separately from reckless driving in order to provide police and the courts more options for addressing negligent behavior that contributes to the injury of innocent people. A careless driving law can meet many of the desired objectives of a “vulnerable road user law” except that it applies equally (and justly) when the victim of a carelessness-induced crash was inside a motor vehicle. The law would also apply equally when a careless bicyclist injures a pedestrian.

5. Preserve Non-Discriminatory Treatment of Bicyclists

Recommendation: Preserve bicyclists’ existing roadway rights equal to other drivers of vehicles; do not enact new bicycle-specific restrictions on bicyclists’ use of roadways or portions of roadways.

Justification: Bicyclists’ ability to access their destinations of choice require that they be allowed use of all roadways except fully controlled access highways which feature no driveways or at-grade crossings (i.e. freeways, which are the only public roads prohibited to non-motorized vehicles, via NCAC 19A.2E.0409). Bicyclists’ ability to maximize their safety requires that they be able to negotiate traffic with the same rights and using the same basic rules of movement that apply to all other vehicles including other non-motorized vehicles. Successful defensive bicycle driving without the threat of harassment by motor vehicle drivers or police officers requires that bicyclists continue to have use of a full marked travel lane, as permitted by NC law like any other driver, when they deem it advantageous. Existing NC traffic law treats bicyclists’ use of a marked travel lane the same as other drivers. (See attachment for details on defensive bicycle driving techniques in marked travel lanes.)

6. Do Not Make Bikeways Mandatory-Use

Recommendation: Preserve bicyclists’ existing right to use general purpose travel lanes regardless of the installation of a nearby bikeway such as a multi-use path or bike lane.

Justification: Experienced bicyclists often find general purpose travel lanes to be better designed, maintained, and utilized for their bicycling purposes than are designated bicycle facilities, which can be popular with novices. Bicyclists using designated bicycle facilities routinely encounter hazards including conflicts with turning and entering traffic, car doors that might open, pedestrians, poor sight lines/distances, inadequate maneuvering space, poor pavement, and debris. Knowledgeable bicyclists avoid bicycle facilities in favor of the general purpose travel lanes where they are concerned about the potential of such hazards. Bicyclists must also leave typical bicycle-specific facilities when preparing for a left turn, when passing other bicyclists, and to make groups more compact in length (such as when maximizing throughput at a traffic signal). Laws that restrict bicyclists’ use of general purpose travel lanes when a bikeway is present interfere with defensive bicycle driving practices, create friction between bicyclists and police, and have a chilling effect on bicycling. (See attachment for details on defensive bicycle driving techniques. See also http://bikeleague.org/content/bike-law-university-mandatory-use-separated-facilities for the League of American Bicyclists’ position on mandatory use laws. )

May 25 2015

Elementary Students Promote Safer Bicycling Habits in Video

PSA created by students for their peers encourages better practices

Elementary School Kids Provide Bicycling Tips on Vimeo.

Bike Month has been busy for students and parents at Northwoods Elementary School in Cary. Shortly after a record turnout for Bike to School Day, the PTA learned that their proposed project to improve bicycle, wheelchair and stroller access to the school was a finalist in a national competition to win a $25,000 grant from State Farm. (To vote for their cause, go to http://tinyurl.com/rampvote.) Two recent tragedies involving child bicyclists in Cary and Wake Forest sparked increased interest in safety and skill development for child bicyclists, so the PTA elected to include bicycling education as part of their social media campaign. Their latest product is a video featuring children demonstrating and explaining a number of recommended bicycling techniques on the types of neighborhood streets where elementary age children most frequently ride. The video addresses the most common types of car-bike crashes for children, including “ride-out yielding” errors, wrong-way bicycling, and other unpredictable movements.

May 12 2015

School Bike Path Enters Finals in Grant Competition

Northwoods Elementary PTA Seeks the Public’s Votes

Accessibility at Northwoods Elementary: Our Story on Vimeo.

Construction of a wheelchair and bicycle facility designed by NCSU students for Northwoods Elementary School in Cary could be funded through a competitive philanthropy program of State Farm Insurance. PTA members entered the project, which addresses existing access issues, into State Farm’s Neighborhood Assist Program this year. On May 8th the school learned that they had been selected as one of 200 projects across the country to compete for 40 grants of $25,000 each. A public Facebook-based voting phase is being held from May 14 – June 3, 2015 to determine which 40 projects are funded.

The Northwoods Elementary community is turning to social media to ask for votes from anyone who supports biking and walking to school. Student demand for walking and cycling is high at the Title I school, which sits adjacent to a town greenway and is surrounded by homes, but the main route into the school grounds consists of a tall concrete stairway. Safety has been a concern as kids continually attempt to roll their bikes up or down the steep slope next to the stairs and parents attempt to carry strollers with infants in their arms. The only alternative route requires kids to take a detour onto a thoroughfare at rush hour to enter the busy school driveway, crossing the heavy flow of bus and car-pool traffic not once, but twice. On national Bike to School day 2015, 85 students rode to school on the greenway, but police traffic control was required to manage the school entrance safely. The community hopes that the proposed path and ramp connection will allow students to bike to and from school independently and facilitate access by users of wheelchairs and child strollers.

According to the State Farm Neighborhood Assist competition rules, any Facebook user can vote for a project up to ten times per day, and can vote every day of the voting period. To help these students with your vote, see the public voting site for the Northwoods Elementary Bike Ramp/Path. For more information, see the PTA’s Facebook note for the project.

May 05 2015

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.

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

multiplethreat — 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.

Apr 28 2015

Understanding Pedestrian Signals

At signalized intersections lacking pedestrian signals, crossing pedestrians are regulated by the vehicle traffic signals. Unfortunately, vehicle signals have a shorter clearance interval than pedestrians may need to finish crossing wide intersections. This can trap pedestrians in the middle of the intersection when the light turns red and conflicting movements begin. Some vehicular signals, such as green right turn arrows, create special conflicts for pedestrians at the crosswalk. When no vehicles are present, demand-actuated vehicle traffic signals may never change to allow a pedestrian to cross legally. Lastly, some mid-block locations are dangerous for pedestrians to cross without signal protection. Pedestrian signal heads and detectors were developed to address these problems. However, poor implementations and public confusion about ped signals can limit their effectiveness.

The Manual on Uniform Traffic Control Devices (MUTCD) defines the meanings for pedestrian signal head indications in the United States. These meanings appear below.

A steady WALKING PERSON (symbolizing WALK) signal indication means that a pedestrian facing the signal indication is permitted to start to cross the roadway in the direction of the signal indication, possibly in conflict with turning vehicles.

The pedestrian shall yield the right-of-way to vehicles lawfully within the intersection at the time that the WALKING PERSON (symbolizing WALK) signal indication is first shown.

A flashing UPRAISED HAND (symbolizing DONT WALK) signal indication means that a pedestrian shall not start to cross the roadway in the direction of the signal indication, but that any pedestrian who has already started to cross on a steady WALKING PERSON (symbolizing WALK) signal indication shall proceed to the far side of the traveled way of the street or highway, unless otherwise directed by a traffic control device to proceed only to the median of a divided highway or only to some other island or pedestrian refuge area.

A steady UPRAISED HAND (symbolizing DONT WALK) signal indication means that a pedestrian shall not enter the roadway in the direction of the signal indication.

Pedestrian Signal Duration

The duration of the flashing upraised hand indication (also known as the pedestrian change interval) is based on the time a pedestrian will require to walk across the street at a speed of 3.5 feet per second. Many people misinterpret the meaning of the flashing upraised hand indication, believing that pedestrians are not allowed to be in the intersection during its display. As a result some motorists harass or endanger pedestrians during the flashing hand phase, and some pedestrians express alarm when the flashing hand starts early in their crossing. At especially wide intersections, most of the crossing time will be spent with the flashing hand indication. This can lead many pedestrians to start crossing during the flashing hand whether they have time to finish or not.

To address these problems, the MUTCD now requires pedestrian countdown timers to be installed wherever the pedestrian change interval is over seven seconds long. This underscores the meaning of the flashing hand and informs pedestrians of exactly how much time they have to finish crossing. Studies have shown that countdown timers increase the percentage of pedestrians who complete crossing before steady upraised hand is displayed even though some faster pedestrians enter the crosswalk late.

The vehicle signal for traffic parallel to the pedestrian’s path will usually turn red after the end of the pedestrian change interval, but at some demand-actuated signals the green may be extended depending on the detected traffic pattern. A pedestrian signal that is programmed to persist the WALK plus pedestrian change interval to last the full duration of the vehicular green signal is referred to as operating in “rest in walk” mode. This is the preferred mode for pedestrians because it maximizes pedestrians’ opportunity to begin crossing the street. Conversely, a signal that is programmed to end the pedestrian change interval before the end of the vehicular green is undesirable for pedestrians, and is associated with lower pedestrian compliance rates. This mode is sometimes used in areas where pedestrian volumes are so high that traffic engineers want to stop the pedestrian flow in order to facilitate motorists’ turning movements.

Pedestrian Detectors

In the ideal case, pedestrians would receive a WALK signal without having to do anything. The signal would change on its own in a reasonable time and display the WALK signal. This is the case in many downtown areas, where traffic signals operate entirely on timers, and a WALK phase is included for each leg of the intersection on every signal cycle. In areas where signals are activated by the detection of traffic, things are more complicated. If no vehicles arrive at the intersection headed in the pedestrian’s direction, the signal will never change unless it detects the pedestrian waiting. This detection is most commonly done with a pushbutton. Passive pedestrian detection systems also exist, but are uncommon due to their expense.

Sometimes a detected vehicle will activate a green vehicle signal, but the corresponding WALK signal doesn’t appear. This is common where traffic engineers seek to optimize signals for drivers on wide intersections with infrequent pedestrian traffic. Including a seven second WALK light plus a long pedestrian change interval in every signal cycle could increase delay for motorists, so traffic engineers often program the signal to only include pedestrian phases if a pedestrian has been detected. As a result, pedestrians often encounter signal cycles lacking a pedestrian phase, because they did not see the pushbutton, did not realize the requirement to push it, or did not reach it in time. This is especially frustrating when pushbuttons are poorly located. A signal that is programmed to provide a pedestrian phase with every cycle is referred to as programmed for “pedestrian recall;” this mode is preferable for pedestrians and results in improved pedestrian compliance rates. Note that by keeping crossing distances short at intersections, such as through road diets or avoiding road widening, pedestrian change intervals can be kept short enough that traffic engineers will be more likely to program the signals for pedestrian recall.

Leading Pedestrian Interval

When a green vehicle signal phase and pedestrian WALK phase start at the same time, this can create a race between drivers and pedestrians to get to the corner first, where pedestrians can find themselves cut off by right turning drivers. A signal programmed with a leading pedestrian interval will illuminate the WALK signal a few seconds before the vehicle green. This gives waiting pedestrians a head start across the intersection and puts them in a location that is more conspicuous to turning drivers prior to the green light.

Accessible Pedestrian Signals

To accommodate visually impaired pedestrians, pedestrian signals may include audio cues such as recorded speech instructions or tones. These acoustic features of accessible pedestrian signals are still the subject of ongoing standards development and are not yet required at all pedestrian signal locations at the time of this writing, but the ADA Public Right-of-Way Accessibility Guidelines (PROWAG) are headed in that direction.

HAWK Beacons

Another type of pedestrian signal, used at mid-block locations, is the HAWK beacon (High-Intensity Activated crossWalK beacon), officially called Pedestrian Hybrid Beacon. A HAWK beacon looks like any other pedestrian signal to the pedestrian facing the crosswalk, but the vehicle driver sees no signal illumination until a pedestrian wants to cross the road. When the HAWK beacon is activated, the vehicle signal displays a succession of flashing and steady yellow then red indications prior to beginning the pedestrian phase. The vehicle signal returns to a flashing red (equivalent of a stop sign) during the pedestrian changeover and goes dark at the end of the pedestrian phase. HAWK beacons can be useful for improving the safety of pedestrian crossings at locations where pedestrian volumes do not meet MUTCD warrants for conventional traffic signals.

Rectangular Rapid Flash Beacons

Another type of signal used to augment mid-block crosswalks is the Rectangular Rapid Flash Beacon, or RRFB. RRFBs are flashing yellow lights that alert drivers when a pedestrian is crossing at an uncontrolled crosswalk, i.e. where a normal traffic signal is not in operation. RRFBs do not regulate when pedestrians may cross, but increase the safety of their crossing. RRFBs are co-located with crosswalk signs, typically on both sides of the roadway and in the median. Activation of the beacons is accomplished by pedestrian pushbuttons or passive pedestrian sensors. Studies have shown that RRFBs increase motorist yielding rates, in one experiment from a baseline of 28% to an average of 93%.