Lidar system aids local law enforcement in catching speeders

By Brett Wilkison • • June 18, 2009

Drivers beware.

Local law enforcement has a new tool to track down heavy-footed motorists. Hand-held units use a technology known as "lidar" short for Light Detection and Ranging — to measure vehicles — speed.
The device is similar to standard radar units used for decades to patrol roadways. But instead of sensing radio waves, lidar pronounced "lie-dar" picks up on light particles, allowing it not only to determine speed but to measure distance to a selected vehicle.
Think of it as "Smokey and the Bandit" meets NASA.
"I can pick out every single car in a bunch and tell you exactly what speed they're going," Visalia police Agent James Andrews said.
Such detection is not as feasible with radar, which sends out a broad, cone-like pulse of radio waves that is not as selective in heavy traffic situations, Andrews said. With lidar's more line-like pulse of light, officers aim the unit through an eyescope and pull a trigger.
Officers stress that they use lidar, like radar, to confirm the speed they estimate a vehicle to be traveling.
"It's just another tool in the tool box," Andrews said.
Lidar equipment has become popular among law-enforcement agencies over the last two years, though the technology itself has been around for decades and has been widely used in military, mapping, meteorology, physics and geology applications.
Local results

Through a federal grant program, the Visalia Police Department purchased 10 of the $2,000 lidar units, assigning them to motorcycle officers at the beginning of this year.
The Visalia office of the California Highway Patrol has used its four units for about a year.
Lidar has proved its value on the streets of Visalia, Andrews said. It's helpful in patrolling restricted-speed zones such as school areas and can assist in measuring distances involved at accident scenes.
Speeding tickets shoot up

The technology has contributed partially to the near-doubling of speeding citations given out by Visalia police in the first half of this year compared with the second half of last year, Andrews said. ‘™¯Because lidar can be more accurate picking a single speeder out of heavy traffic, Officer Brent Miller said, tickets are more likely to hold up in court.

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"There's a lot less room for error," he said.

Miller said he still prefers radar. It doesn't require a scope to aim, doesn't get blocked by garbage cans or other obstacles and is better at close range where visibility is limited, as where a road bends, he said.
It's up to officers to decide which tool to use, Andrews said.
At an intersection off Cameron Avenue west of Mooney Boulevard last week, Miller and Andrews put lidar and radar to a side-by-side test. The radar unit, held by Miller, produced a long squeal as it honed in on a group of cars. Andrews, meanwhile, aimed the lidar unit at specific vehicles, pulled the trigger and got a quick, single beep.
"That one's going 33 [mph]," he said, sitting on his motorcycle in a 45 mph zone. "Everybody's behaving right now."
Radar detectors

The introduction of lidar means bad news for drivers who've invested in radar detectors in an attempt to avoid tickets. Those detectors don't help with the new lidar units, Andrews said.
Of course, Laser Technology, the same company that makes the lidar units for law enforcement, also sells lidar detectors for drivers. But officers say those devices and the ubiquitous radar detectors are of little use.
Lidar units and newer radar units only give out signals when a vehicle has been targeted by an officer, they said.
"By the time [the detector] beeps," Miller said, "we've already got you."