The term “photo radar” is frequently only half right. Yes, the system always snaps a photo of a vehicle it considers to be speeding, but it doesn’t always measure that speed with radar.

Back in the eighties when it began appearing in a few U.S. municipalities, “photo radar” was the name applied to a mobile system using European equipment such as the Swiss-made Multanova. These devices were, and still are, packaged in vans. The enforcer drives to a location, at which point he makes a quick set-up that includes positioning a radar gun on a tripod along the road and aiming his cameras. The radar beam, almost always Ka band, is angled across the road, thereby weakening the signal available to approaching radar detectors.

After an hour or two in one location, these photo-radar units usually move on to a new ambush.

Camera enforcement of traffic speed doesn’t always use radar, however. In fact, non-radar systems are on a fast growth track now. There are four types you should know about:

1. Speed On Green. Red light cameras are used in more than 100 U.S. communities, according to the Insurance Institute for Highway Safety. Many of these systems use wires buried in the pavement to sense when cars enter the intersection. With a software change, many of these systems can be updated to do a time-distance calculation between the buried sensors, thereby indicating vehicle speed. If a violation is detected, the cameras already in place for red-light monitoring will picture the accused speeder. And the ticket will be issued by the same system in place for red-light violations. Adding this speed-on-green feature brings automated speed enforcement on the cheap.

V1 warning on this threat: None; it’s neither radar nor laser.

Speed On Green

2. Permanent Speed Cameras. Early in 2006, camera enforcement began along the 101 freeway in Scottsdale, AZ, with three cameras monitoring each direction over a 7.8-mile stretch. This is the first photo-speed enforcement on a U.S. freeway. The equipment is owned and operated by Redflex Traffic Systems, Inc., a wholly owned subsidiary of an Australian company, Redflex Holdings Ltd.

These cameras are triggered by piezo loops buried in the pavement, a separate loop for each of three lanes. This allows the system to know which vehicle to accuse. Photos are taken by two cameras mounted on posts along the right side of the road, one shooting a front view to capture the driver’s face, the other aimed at the rear license plate.

V1 warning on this threat: None; it’s neither radar nor laser.

Speed Camera

3. Photo Laser. Redflex says it has one fixed-in-place camera-enforcement system using laser to measure speed, now operating in a mid-western U.S. city. It also offers a version of the van-based mobile system that substitutes laser for the radar. We can’t predict the growth rate of these laser systems. For sure, they will present a challenge to the idea of early warning from a laser detector, but they certainly will not be immune to detection.

V1 warning on this threat: Maybe, depends upon the situation.

4. Point-to-point speed systems. These systems are intended for limited-access highways where they would measure time intervals for each vehicle between points several miles apart or even farther. Imagine an automated VASCAR on a giant scale. Such a system would have beginning and end points, each consisting of an overhead structure with vehicle-recognition sensors covering each lane. One sensor array records each vehicle entering the monitored stretch, another watches the exit. If a vehicle traverses the distance faster than allowed, its picture is taken by cameras along the road.

No systems of this sort are operating in the U.S.

V1 warning on this threat: No; this is a vehicle-recognition system not capable of measuring instantaneous speeds.

Automated speed enforcement is sure to grow. Cities have found the promise of revenues to be irresistible. Redflex is now the largest of the contractors supplying photo-enforcement services within the U.S. Its primary business has been red-light cameras, but it’s telling investors that community support is emerging for speed cameras and it expects the U.S. market will grow to $4-10 billion dollars, even larger than the red-light business which, it says, has the potential to reach $1-3 billion.