What is a Sensor Loop?

Sensor loops are copper wires that are installed in the pavement that trigger a light change when metal is near them.  You may have noticed these loops at some intersections – they are cuts in the pavement that are about 5’ or 6’ square.  Sometimes there are two to three of these “boxes” lined up just before the stop line.  They are all connected, and all of the wires run to the traffic control box at one of the corners. 

Lunalilo Home Road / Hawaii Kai intersection. All cuts are part of the sensors.

The way a bicyclist triggers the sensor is by putting the bike right on the sensor line.  According to a technician at the City Department of Transportation Services, 99% of bikes should be capable of triggering the sensors here – there is enough metal in the wheels, chain, chain ring, cranks, etc. to do so.  I recommend you ride right on the lines of the sensors and stop at the very top part.

Bicyclists approaching the stop line. There are two sensor loops here.

Bicycle wheel when it is right on the line, at the top of the loop.

Bicycle on the entire line.

Myths:  According to the city technician, magnets do not trigger the loop to change the signal.  In addition, weight has nothing to do with these loops.

Information Courtesy of Natalie Iwasa

For More Information :

Detection of Bicycles... Dr. Steven Goodridge

How to Turn Signals Green humantransport.org

Making Signal Systems Work for Cyclists USDOT Federal Highway