• Two types of detection device are available for speed detection, radar and laser. Both have pros and cons and specific applications for different scenarios.
• Radar is a cheaper option, however because of a large 'cone' effect, will only effectively detect the speed of the lead vehicle in a line, whereas a laser, with a smaller 'cone' effect, can pin point a particular vehicle which may be gaining speed to join the rear of a line of moving traffic, effectively looking 'past' other moving traffic.
• Radar is useful in detecting the speed of a motorcycle as the large 'cone' effect encompasses the motorcycle, and there is not a need to be pin-point accurate.
• For most speed watch applications radar should suffice, mainly because of the cost implications, but also because the speed check performed by a Speed Watch will not form the main evidence of any court trial, there is not the requirement for pin point accuracy.

A typical radar device

A typical laser device

The Devon and Somerset Fire and Rescue service will visit various locations to support a Speed Watch, using mobile Speed Indication Displays. (SID). These displays monitor vehicle speeds and display the speed on a large screen for all to see. They display speeds under the speed limit as well as above.

A typical SID (Speed Indication Display)