What Are Loop Detectors and Are They Worth Closing the 101 For?

Installing the gadgets means partial closures through Wednesday

Two nights down, two nights to go: Caltrans is instituting partial closures on the Hollywood Freeway for the next two evenings, between midnight and 5 a.m. from Glendale to Cahuenga boulevards.

Part of the closures stem from a $19 million repaving project between Hollywood and DTLA, but the transportation agency says the work is also necessary for the implementation of “loop detectors,” which calculate real-time traffic information. When cars travel over the “loops,” a current is sent to a sensor, and Caltrans and Metro receive updates every 30 seconds.

“A wire loop is activated by an electronic signal ranging from a 10 to 200 kilohertz frequency, which creates an electromagnetic field,” according to Caltrans. “When a vehicle passes over the loop or stops on top of it, the vehicle’s undercarriage acts as a conductor that interferes with the electromagnetic field. Electronic measurements, communication and various mathematical algorithms are used to generate data and information about traffic flow volumes and occupancy, speeds, travel times, and the approximate location of an incident.”

Loop detectors are far from new. They’ve been around for 40 years, with over 25,000 detectors embedded in California freeways. Having more information is hardly a salve for traffic anxieties, but as we’ve witnessed with Waze, simply having more information can go a long way to reducing road rage.