Speed Sensitive Signals

Boulder, Colorado.

Some agencies have installed innovative traffic control measures, such as speed sensitive traffic signals, to reduce motor vehicle speeds. These devices involve using pavement loops to detect the speed of a motor vehicle. If the speed exceeds the speed limit, the traffic signal ahead will display a red light. Drivers learn that speeding on such streets will require them to stop at the traffic signal and be further delayed. This treatment is not applicable to local streets inside neighborhoods that do not have traffic signals, but can be applicable to collector and some arterial streets. Some communities are timing their traffic signals to a preset reasonable speed. Motorists who exceed the preset speed will be stopped at the next traffic signal. Signs with SIGNAL SET AT XX MPH can be installed along the street to alert drivers.

Putting It Into Practice: Speed Sensitive Signals

Boulder, CO; Arlington, VA; and Washington, D.C.

High-speed motor vehicles pose a serious threat to the safety of children who are crossing arterial streets near schools and are one of the largest challenges in providing safe routes to school. Innovative measures have been used to reduce motor vehicle speeds such as the speed sensitive signals used in Boulder, CO, Arlington, VA and Washington, D.C.

The signals use pavement loops to detect the speed of a motor vehicle. If the motor vehicle exceeds the speed limit, the traffic signal ahead displays a red light. Drivers learn that speeding on such streets will require them to stop at the light and be further delayed. The sign “speed sensitive signal” conveys that message to drivers.

Speed sensitive signals were added in as part of a traffic calming project done at Sunnyslope High School in Phoenix, Arizona. The signals monitored motorists speed and flashed their driving speed and a bright LED strobe light if a motorist exceeded the 35 mph speed limit by 5 mph or more.

Along with other traffic improvements, including a staggered crosswalk, the speed sensitive signals resulted in slower motorist speeds (on average cars went 6 mph under the speed limit) and a reduction in pedestrian crashes. The avenue averaged 32 pedestrian crashes per year during the previous three years, but only one crash in the six months following the project (PEDSAFE, 2013).