do radar detectors work in motion?

[Maverick2002]

So, here's my Friday night. Mom just called, saying she got a ticket. She claims she was certain the cop was DRIVING towards her on the other side of the street. When she saw him, she slowed down. He turned around and followed her for a while before activating his lights. He then gave her a speeding ticket; she asked if he used a radar and he said yes.

My question is: can radars work when the cop car is in motion? How does it account for the car's speed???

 

[Pepsi90919]

...it subtracts the cop's speed........

 

[MercenaryForHire]

She probably got paced by him during that "followed her" period.

- M4H

 

[Kalvin00]

Originally posted by: Pepsi90919
...it subtracts the cop's speed........

 

[Maverick2002]

Well, she claims she slowed down to the legal speed as she saw him turning around and following her, so I'm assuming she was going legal speed then.

 

[jpeyton]

Radars can typically track the fastest object and they do account for the motion of the cop's car.

Fight it in court.

 

[acemcmac]

why wouldn't you take evasive action the second you think you're about to have an issue?

 

[Ulfwald]

Basically, the radar works on a closure rate. Lets say your mom is doing 80, and the cop is doing 60, your moms speed would register at 140. Also, he may have followed her until he got confirmation back that the car was not stolen, or registered to a known felon.

 

[Pepsi90919]

the last time i was pulled over was when a cop nailed me coming in my direction, he got my speed about half a kilometre down the road. using the newest technology they can 'lock on' to your speed (that is, it's 100% sure) and also give you a "maximum" speed (for me, i was 'locked on' at 108 km/h and a maximum of 113 km/h)

 

[wischeez]

Cosine Effect on Moving Radar: Moving Radar measures closing speed between the radar and target. The radar also measures patrol car speed (from the ground echo) to calculate the target speed. (Target speed=closing-patrol car). This introduces additional sources of cosine error. In most situations the angle between the radar and target is the major error source and favours the target (measure too low). However if the antenna is misaligned (off patrol car direction) the patrol car speed may measure low resulting in target speed measured too high.

Moving Radar Variables: Target speed will only measure higher than true speed when the target is approaching the patrol car AND the cosine angle between radar and target are small, (typically less than 5%) AND the angle between the patrol car and the ground is large, (typically greater than 5%). Patrol car and target speeds are significant, patrol car speed greater than target speed increases the error. (The greater the difference the larger the error and the higher the measured speed).

 

[Zorro]

Your mom knew she was speeding thats why she slowed down. Pay up now..

 

[Zenmervolt]

Originally posted by: jpeyton
Radars can typically track the fastest object and they do account for the motion of the cop's car.

Fight it in court.

Modern radar systems used by most police departments will display all readings, not just the strongest.

It used to be that staying next to a semi would mask your car's radar signature since the semi's signature was so much larger, but now radar can display multiple returns.

ZV

 

[OulOat]

Originally posted by: Maverick2002
When she saw him, she slowed down.

So she was speeding?

 

[spidey07]

Originally posted by: Maverick2002
So, here's my Friday night. Mom just called, saying she got a ticket. She claims she was certain the cop was DRIVING towards her on the other side of the street. When she saw him, she slowed down. He turned around and followed her for a while before activating his lights. He then gave her a speeding ticket; she asked if he used a radar and he said yes.

My question is: can radars work when the cop car is in motion? How does it account for the car's speed???

yes, it measures the difference between her and the surroundings.

 

[thomsbrain]

yes, they work in motion, they are built into the front and backs of many police cruisers. they just subtract or add the cops speed to their own readings.

 

[Chompman]

You have to remember also that radar detectors are illegal in some states so she is lucky that wasn't one of them.

 

[lobadobadingdong]

Originally posted by: Zenmervolt

Originally posted by: jpeyton
Radars can typically track the fastest object and they do account for the motion of the cop's car.

Fight it in court.

Modern radar systems used by most police departments will display all readings, not just the strongest.

It used to be that staying next to a semi would mask your car's radar signature since the semi's signature was so much larger, but now radar can display multiple returns.

ZV

The only problem is they are still often wrong as to which one was speeding, I dont' know how many times I've gone wizzing past someone (to pass them, I actually drive the speed limit most of the time), and the person I just passed got pulled over (when it was me speeding in the first place.

 

[Iron Woode]

Originally posted by: MercenaryForHire
She probably got paced by him during that "followed her" period.

- M4H

A great thing to do in Ontario if you get pulled over for speeding:

ask the officer to show you the radar displaying your speed. He is required by law to show you. If he does not have radar or didn't turn it on (ie: he paced your speed) he cannot write you up a ticket because he will be required to show proof. Radar is the only proof traffic court accepts.

 

[The Stigenator]

ya radar can be read while in motion. A friend got a 60 in a 35 in LA once and the cop was on the other side of the street, i mean the guy turned on ihs light right when he blew by him, he knew he was dead by then.. the cop pulled a U turn and pulled him over. He got a reckless endgaerment.


Radar detectors, even teh el cheapo ones will save your butt. Last weekend I was coming back from LA, and right when i entered sacramento city limits i was going around a turn and about 5 seconds before i entered the curve on the freeway the dettector went off saying "Ka alert", i quickly braked and came to a regular speed. I was doing 85/65.

Prior to that incident, on the way to sacramento, i found it give off a Ka Alert about 1/2 mile before i saw the cop on the freeway. He was on the other side. That is probably the furtherst i have seen on my POS detector.

Mine is from 1999, its an Cobra 9000 series, not sure of the model #. I like it, it works.

 

[simms]

"A great thing to do in Ontario if you get pulled over for speeding:

ask the officer to show you the radar displaying your speed. He is required by law to show you. If he does not have radar or didn't turn it on (ie: he paced your speed) he cannot write you up a ticket because he will be required to show proof. Radar is the only proof traffic court accepts. "

Thank you for this tip! Unfortunately what backing do you have behind this.. is this in legistlature or anything? A document I could print out perhaps?

 

[jagec]

Originally posted by: TheGoodGuy
Radar detectors, even teh el cheapo ones will save your butt. Last weekend I was coming back from LA, and right when i entered sacramento city limits i was going around a turn and about 5 seconds before i entered the curve on the freeway the dettector went off saying "Ka alert", i quickly braked and came to a regular speed. I was doing 85/65.

They'll catch you eventually, by hiding near supermarket doors/speed indicator signs, or by using laser.

The best defense is free: Just keep it to 10 over, and make sure you're not the fastest car on the road.

 

[TheLonelyPhoenix]

Originally posted by: jagec

Originally posted by: TheGoodGuy
Radar detectors, even teh el cheapo ones will save your butt. Last weekend I was coming back from LA, and right when i entered sacramento city limits i was going around a turn and about 5 seconds before i entered the curve on the freeway the dettector went off saying "Ka alert", i quickly braked and came to a regular speed. I was doing 85/65.

They'll catch you eventually, by hiding near supermarket doors/speed indicator signs, or by using laser.

The best defense is free: Just keep it to 10 over, and make sure you're not the fastest car on the road.

:thumbsup: :beer:

 

[phonemonkey]

Originally posted by: jagec

Originally posted by: TheGoodGuy
Radar detectors, even teh el cheapo ones will save your butt. Last weekend I was coming back from LA, and right when i entered sacramento city limits i was going around a turn and about 5 seconds before i entered the curve on the freeway the dettector went off saying "Ka alert", i quickly braked and came to a regular speed. I was doing 85/65.

They'll catch you eventually, by hiding near supermarket doors/speed indicator signs, or by using laser.

The best defense is free: Just keep it to 10 over, and make sure you're not the fastest car on the road.

Some police depts also use instant-on for radar, or just hide the gun behind their car door to deflect the radar energy (I got caught this way for my first ticket).

 

[dman]

Bummer for your mom. Hopefully she hasn't had a ticket in a long time and it won't make her insurance jump. If she got a ticket for doing more than 10-15 over, well, probably worth it to go to court and see if the judge will lower it at least.

 

[Iron Woode]

Originally posted by: simms
"A great thing to do in Ontario if you get pulled over for speeding:

ask the officer to show you the radar displaying your speed. He is required by law to show you. If he does not have radar or didn't turn it on (ie: he paced your speed) he cannot write you up a ticket because he will be required to show proof. Radar is the only proof traffic court accepts. "

Thank you for this tip! Unfortunately what backing do you have behind this.. is this in legistlature or anything? A document I could print out perhaps?

I asked the cop that pulled me over and accused me of doing 65 km/h in a 50 km/h zone. I was doing 48-50 km/h when he paced me. Before that I talked to another officer about radar and he told me always to ask for the radar speed.

In Ontario you can call Points. They deal with traffic violations and are made up of former traffic cops and judges.

http://www.pointts.ca/