# Thread: Question: COP(LEO??) in motion....

1. ## Question: COP(LEO??) in motion....

Just wondering, as one of my "old" (tickets 3+ years back) was this way...

how accurate is radar and/or laser , while the officer is MOBILE (let's say 30+mph), and traveling in the other direction? I was alwasy under te impression, that to correctly gauge the speed of an object, the unit/gun itself had to be immobile.....true? not true?

this instance in particular, I was driving back to work, after lunch. Headed down one of our "country" roads, I wasn't really looking at my speed. As I approached a small upgrade, a cop came over the top heading in the opposite direction. As I crested the top, I could see in my mirror he was turning around. I got pulled over, and he told me he got me at 40mph, and it's 25. (small, country road.....NO ONE, and I mean NO ONE drive 25...at least 35, 24-7. )

Anyway, just curious......

2. It's def. legal, and possible, but the question is how accurate is it. Basically, he has two "speed measuring devices", one measuring other cars, and another measuring his own speed. Then his unit just adds, or subtracts his speed to the speed he is getting from you.
For example, you are coming at him at 50 mph. He is going 50 mph. Together, that is 100 mph closing speed, but his unit is supposed to subtract his speed, there fore resulting in your speed.

But it has been shown that this meathod is rather error prone.

3. I always thought this is one I SHOULD have argued in court.....oh well, what's past is past. Good to know though!

4. yep moving radar works well. There is the possiblity for error, but the readings will normally be way off.

Also, no such thing as moving laser...well that actually works to clock other vehicles speeds.

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