Technical Resources

Signal Detection for Bicycles

Traffic Signals

Traffic signals are used to assign and manage right-of-way at intersections. Signals promote the orderly movement of traffic and prevent excessive delay. As technology have improved, traffic signals have moved from simple timers, where all movements can be given a specific amount of time, to on-demand systems that keep the main traffic moving until a vehicle needed to turn. Then, the signal is notified of the waiting vehicle by a detection device. Similar ssystems exist for pedestrians, but are usually accommodated with a push button detector or in recall. However, the detection device that was commonly used for heavy motor vehicles did not always detect bicycles and the cyclist was faced with the following three choices:

  • Wait for a motorist or pedestrian to actuate the signal
  • Get off the bike to push the pedestrian button
  • Treat the signal as “inoperative” and proceed when it is safe to do so

More recently, new advances in bicycle signal detection and an increased awareness of the benefits of bicycle signal detection have created a need for more information on this topic.

 

Detection Devices

There are several detection methods appropriate for bicycles, including inductive loops, video, microwave radar, and push buttons. A brief description of each method is described as follows:

  • Inductive is the most common detection device for vehicles. It consists of insulated loop wire placed in a slot cut in the pavement. Inductive loops can be placed in various configurations and used for detection, counting, or speed measurements. Certain design techniques and loop patterns are often used to increase the loop’s ability to effectively detect bicycles. Pavement markings can also be provided in conjunction with the loop detectors to denote the optimal location for a cyclist to position their bicycle in order to be detected.
  • Video detection systems use cameras—typically mounted overhead—to detect vehicles, including bicycles. Video is a good option when there is a need to avoid cutting the pavement to install inductive loops or when right-of-way limitations make loops impractical. Video detection can be used in conjunction with other types of detection at intersections. A negative regarding video detection is that it can be affected by inclement weather, glare, or day-to-night transitions.
  • Microwave radar devices are a viable detection option for bicycles, especially when there is a need to avoid pavement cuts or when other options such as video are determined to be not as effective. These devices emit waves that are then reflected back to the receiver where the detection is made. Many microwave detectors can be used to also measure volume, speed, and vehicle classification. Microwave radar functions well in inclement weather, glare, and low-light conditions and can be set to detect multiple traffic lanes.
  • Push buttons, which are typically used for pedestrian detection at signalized intersections, can also be employed for bicycle detection. Push buttons are mechanical user-activated devices typically used at signalized intersections to provide actuation for pedestrian movements. These devices can also be used in certain circumstances to provide detection for bicycles. While push buttons are usually a low-cost solution and are reliable, they are not suitable in certain situations, such as when a bike lane is not adjacent to the curb line. To be effective for cyclists, push buttons should be easy for cyclists to reach without dismounting.

For a detailed description of detectors, refer to the U.S. Department of Transportation Traffic Control Systems Handbook, Chapter 6. https://ops.fhwa.dot.gov/publications/fhwahop06006/chapter_6.htm.

Phasing

Figure 4. Near side and far side bicycle signals showing in red phasing at busy multimodal intersection in Santa Monica, California, USA. Source: PBIC/Toole Design Group.

 

Bicycle Signal Detection Guidance

It is imperative that a detection device be included on a bicycle facility to detect waiting bicyclists and provide right-of-way indications on separated bicycle signal heads unless the bicycle signals are incorporated into a fixed time operation and automatically displayed each signal cycle. The following links provide information related to bicycle detection:

ALTA Bicycle Detection White Paper
Provides a review and analysis of available technologies and practical experience related to bicycle detection, including detection types and possible enhancements. https://altago.com/wp-content/uploads/ALTA_Bike_Detection_White_Paper_July2021.pdf 

NACTO Urban Bikeway Design Guide
The Urban Bikeway Design Guide includes descriptions of four primary types of bicycle signal detection, their applications, and benefits. It includes a list of required and recommended elements to make bicycle detection work properly.
https://nacto.org/publication/urban-bikeway-design-guide/bicycle-signals/signal-detection-and-actuation/

U.S. Department of Transportation, Federal Highway Administration (FHWA)
Bicycle Safety Guide and Countermeasure Selection System
The Bicycle Safety Guide and Countermeasure Selection System provides practitioners with information to improve the safety and mobility of bicyclists. The online tools offer lists of possible engineering, education, or enforcement treatments, including bicycle signals. The first link is to the program. The second link is to Bike-Activated Signal Detection. The online tools include considerations and estimated costs for bicycle signal detection.
http://www.pedbikesafe.org/BIKESAFE/

Pedbikesafe.org
Optimizing Signal Timing for Bicycles
http://pedbikesafe.org/bikesafe/countermeasures_detail.cfm?CM_NUM=35
Bike-Activated Signal Detection
http://pedbikesafe.org/BIKESAFE/countermeasures_detail.cfm?CM_NUM=36

City of Seattle
Seattle Right-of-Way Improvements Manual
Bike Intersection Design: Supporting Intersection Treatments for Bicycle Facilities
This manual serves as a source for design standards regarding the installation of various actuation systems, signal locations, and other features associated with bicycle signals.
https://streetsillustrated.seattle.gov/design-standards/bicycle/bike-intersection-design/

City of San Diego
City of San Diego Traffic Signal Bicycle Detection Study
This 1985 study provides specific detail on placement, configuration, and frequency of loop detectors to achieve optimum performance for cyclists. The technologies evaluated included inductive loop, magnetic loop, and push button.
http://www.cyclelicio.us/files/sandiegobicycledetection1985.pdf