Bicycle Signals and Countdown Timers Galore!

A bicycle signal countdown timer in the Netherlands. The partial white ring around the "WACHT" progressively de-illuminates to show the time until the bicycle signal will turn green.

Someone asked me recently what the coolest piece of transportation infrastructure I've seen in the Netherlands is. The first specific design to come to mind is the bicycle signal countdown timer, devices which employ various types of counters to show the bicyclist the time remaining before a phase change. Broadly, bicycle signal countdown timers are traffic signal countdown timers. These devices count down the time remaining on a signal phase, which, depending on the local jurisdiction's goal for that location, can include green, red, or even yellow signal countdown timers. 

Green signal countdown timers show the time remaining until the signal will turn yellow. Their purpose is typically safety: they give road users more time to make a stopping decision at the onset of yellow. One would expect this to reduce two common types of crashes at intersections: rear end, due to abrupt stops, and red light running, due to misjudging the yellow interval. However, while some studies show that these timers yield actual safety benefits, others show that the signals encourage drivers to behave more aggressively [1]. Red signal countdown timers show the time remaining until the signal turns green. Their purpose is typically efficiency, the idea being that road users will know how long they have to wait on red and be ready to proceed through the intersection when the light turns green, thus improving what is called "queue discharge" [2]. With the exception of pedestrian countdown signals at intersections, signal countdown timers are currently not used for bikes or vehicles in the US. They are, however, used in various forms in other countries. 

Bicycle signals themselves are rare to see in the US, yet commonplace across the Netherlands. These signals typically consist of a near side traffic light displaying a red, yellow, or green bicycle indication. The signal controls bicycle traffic separately from vehicle traffic, separating bicycles in time from potential conflicts with vehicles. One bicycle-vehicle conflict type that transportation designers spend a lot of thought trying to mitigate is the right-hook conflict. This conflict occurs when a right-turning vehicle fails to yield to a through-moving bicyclist and turns across their path. Bicycle signals can prevent this conflict by giving bicyclists and vehicles separate green indications, instead of letting both users go at the same time. These signals work similar to how signalized intersections protect, say, left-turning traffic from through-moving traffic by using different phases for each. A protected left phase (green left arrow) will stop through-moving traffic so the left-turning vehicles can make their left unencumbered. 

The two bicycle signal countdown timers I've seen here have counted down the time until the bicyclist will receive a green signal indication. One used a numeric countdown, with the time in seconds displayed over the bicycle signal. The second used a symbolic representation, where dots in a circle above the bicycle signal disappeared in a clockwise fashion to show the time remaining on the phase. Using a timer can help improve the efficiency of the bicycle phase by informing bicyclists when they need to be ready to go. When the last dot disappears and the "one" turns to "zero" the bicyclists are prepared to go.

[1] Islam, M. R., Wyman, A. A., & Hurwitz, D. S. (2017). Safer driver responses at intersections with green signal countdown timers. Transportation Research Part F: Traffic Psychology and Behaviour, 51, 1-13. https://doi.org/10.1016/j.trf.2017.08.010.

[2] Islam, M. R., Hurwitz, D. S., & Macuga, K. L. (2016). Improved driver responses at intersections with red signal countdown timers. Transportation Research Part C, 63, 207-221. http://dx.doi.org/10.1016/j.trc.2015.12.008.