CHP vehicle radars/sensors?

[FiveSeven]

Question to CHP or if someone who knows.

If CHP Patrol car is practically tailgating another car and someone passes by, How does patrol officer knows exactly the speed of passing incoming vehicle? Even though passing vehicle is not in the line of sight.

Does side mirrors have radars in them, vehicle is equipped with some sensor/radar that detects incoming traffic when it's passing a patrol car?

As far as I observed, I only see two radars under the windshield and one in the back. I could be wrong.

[infamous1979]

super duper ninja sensors....

[Dannicus]

Those radar sets are not spot beams. They have a bit of a spread. If he's matching the speed of the car in front of him it could pick up an oncoming car and display it's speed as it would have the largest Doppler shift out of any other signal returns. The officer would have to pick out the most logical speed of the oncoming car out of the random erroneous speeds displayed on the unit due to noise.

They don't work very well if multiple vehicles are present. They are meant for a single contact situation and work best when the vehicle the unit is in is stationary.

[FiveSeven]

^

Still, radars need some line of sight, even if it's not pinpoint like a laser..... If the outgoing/incoming signal is blocked by a large van or similar vehicle.....How does it get any reading? Unless those radars have large/wide side angles and are really fast.

[hitman13]

Rear radar

[Dannicus]

^

Still, radars need some line of sight, even if it's not pinpoint like a laser..... If the outgoing/incoming signal is blocked by a large van or similar vehicle.....How does it get any reading? Unless those radars have large/wide side angles and are really fast.

Didn't say the car in front was blocking LOS.

Rear radar

^ Good one!

[FiveSeven]

I did.
Anyway, if it's the rear radar then I"m impressed on quick reaction of some CHP officers.
I guess it takes a lot of practice to hone those skills, a predator-game move in a way (to tailgate someone in order to avid of being spotted).

[TrailerparkTrash]

The radar units in the patrol cars are easy. There is a radar "antenna" both pointing forward and rearward. The officer has a little "mouse" like controller he can keep in his hand and with the simple push of a button, he goes from "FWD" to "Rear" antenna.

So, if the officer is going north on the road and an opposite car goes south, the officer can see his speed both oncomming and when the vehicle passes him to the rear.

And yes, they work great, contrary to popular belief. Not only do they give a visual display of the fastes moving target, but an audio dopler warning as well. So, if a large semi truck is doing 40mph and a little porsche is going 80 down the road but behind the semi, it's hard for the radar to pick it up. However, usually within seconds, the faster moving car is detected either far enough behind the semi, or they pass the semi.

As one poster said earlier, the beam is not like a tight laser beam. It fans out like a shotgun. It tends to pick up the fastest moving target our of a large group of vehicle, so long as that target is closer to the "lead" of the pack or not being blocked by a larger vehicle.

Officer's are not trained just to point the radar and look at the display. They must also use the audio doppler tone, then they must visually verify the faster target by confirming the display, tone and visual speed estimate of that particular vehicle. It's easier to explain in person, rather than typing it here on this thread.

Believe it or not, officers in Cali must go through a POST certified course to be a radar operator. Part of that training is to visually estimate speeds of motor vehicle. All estimates are then recorded and documented in the training packet. That's why an officer can testify in court as to the use of radar, that part of their training and experience was visual speed estimations. Many of the good traffic cops out there can honestly estimate a vehicle's speed and be off by only 2-3 mph! ....and the courts accept that training and that's part of what makes a cop an "expert witness" on the matter in court.

Hope that helps a bit and doesn't confuse any.