Radar speed sign

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Standar Radar Speed Sign with Block Letters. Pictured with solar panel.
Standar Radar Speed Sign with Block Letters. Pictured with solar panel.

A radar speed sign (also called a driver feedback sign, changeable message sign, or variable message 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 unsafe speeds. They are used as a traffic calming device in addition to or instead of physical devices such as speed humps, speed cushions, speed tables, and speed bumps.

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[edit] Usages

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.

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.

[edit] Features and Sign Types

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.

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 and battery packs.

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 in to the signs. Some signs offer a flashing light to warn motorists who exceed a designated speed.

[edit] Effectiveness

Studies conducted both in the UK and in the US have found radar speed signs to effectively slow traffic down. Although speed reductions are traditionally less than those resulting from physical measures, the signs are still an effective measure in slowing vehicle speed.

One sample study conducted in Bellevue, Washington found that radar speed signs resulted in speed reductions between 1-5 mph, although some locations resulted in changes upwards of 5.5 mph. The signs were most effective on streets where vehicles were driving more than 10 mph above the posted speed limit. In the Bellevue study, streets where signs were installed continued to experience speed reductions even four years after the signs were installed.

References?

[edit] Federal Standards

The MUTCD (Manual on Uniform Traffic Control Devices), a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT), has specified standards regarding sign size and letter height for radar speed signs. Many signs on the market do not meet these standards, although All Traffic Solutions, Information Display, Traffic Logix and Radarsign do conform to them.

[edit] Safety of Pedestrians

The use of radar to detect automobile speeds poses little concern of irradiating pedestrians. ["Commonwealth of Virginia RF Radiation Exposure Compliance Plan"]

[edit] See also

[edit] External links