A radar speed sign is an interactive sign, generally constructed of a series of LEDs, that displays vehicle speed as motorists approach. The purpose of radar speed signs is to slow cars down by making drivers aware when they are driving at speeds above the posted limits. They are used as a traffic calming device in addition to or instead of physical devices such as speed bumps and rumble strips.
The devices have been referred to by a wide variety of names, a partial list of which follows: driver feedback sign, radar signs, Vehicle Activated Sign (UK), changeable message sign, Your Speed sign, radar feedback sign, speed radar sign, radar speed display, speed feedback sign, traffic calming sign, speed display board, dynamic speed display (DSDS) or variable message sign.
Radar speed signs are often used in school zones, sometimes in conjunction with Safe Routes to School programs, in construction zones, or on busy residential roads. Some college and corporate campuses use radar speed signs to slow traffic as well. Many plants are using these signs to monitor forklifts and other type trucks. There are steps to placing a radar speed sign.
Speed display signs are sometimes used in conjunction with physical traffic calming solutions. They are also used on streets that cities do not want to put physical measures on either because of snow concerns or traffic volume. Often, cities will use these signs to test streets to determine the need for further traffic calming.
Signs are available in a range of costs with a variety of different features. Manufacturers of radar speed signs abound, ranging in style and features from a basic inexpensive sign to more sophisticated signs with myriad features to help analyze data and improve results. Pole mounted signs that combine speed display with variable message capability are often used in school zones, eliminating the trailer's "footprint".
Standard signs have stationary block letters that display the words "your speed". More advanced models include variable messages such as Your Speed, Speed Limit, and Slow Down, which can be programmed based on motorist speed.
Many manufacturers offer optional solar power, which allows the signs to be powered via solar energy with rechargeable batteries included for nighttime operation. Many users (especially in Northern climates) have reported problems with solar powered signs failing to work during winter months, and with their internal batteries failing prematurely. However, newer proprietary power efficient methods are available as well as cold weather batteries.
Some of the features offered on the higher end signs include focused viewing systems to avoid distractions for motorists in other lanes, vehicle data collection, programmable software that allows you to determine sign behavior, and/or access via portable devices such as Bluetooth or PDAs. Many signs offer tampering and vandalism prevention measures built into the signs. Some signs offer a flashing light to warn motorists who exceed a designated speed. However, many state, county and city traffic engineers in the USA specify only signs that meet the federal guidelines called MUTCD (Manual on Uniform Traffic Control Devices) which, due to safety reasons, eliminate certain distracting features like strobe lights and certain color messages. A Vermont state guideline is very specific and eliminates many features.