How do traffic cameras catch the right vehicle

Factual Questions
1

About a month ago I was driving on a highway late at night and there were road work signs reducing the speed limit and saying the usual - fines are doubled and that the speed limit is photo enforced.

I was driving in the middle lane obeying the speed limit when a small clump of 3-4 cars passed me. One had to be doing at least 70, he passed me on the left, the others passed me on the right. As they all got just in front of me I saw the flashes from the traffic camera.

I’ve been worried about getting a ticket, but I guess I am safe.

How do they know which of us was speeding when we were all in a clump?

2

If the sensor is in the pavement, it will record in which lane and when the speeding car went over it.

3

“flashes”

From a sequence of still photos, how can you tell which vehicle is moving faster? Have I got the question right? :wink:

4

I have seen systems that overlay the vehicle speed on the image, so you would have an image of the vehicle tagged with its speed at that moment.

5

There’s that, and some cameras record video as well.

6

These are EVERYWHERE in MD. My guess is that that combine photographic evidence with radar data. Here, you’re OK if you’re not going more than 13 mph over the speed limit (of course, in work zones, they like to reduce the speed limit without actually posting it).

I’ll grant that it’s actually a pretty good solution that spares LEO time. As a driver, though, it just feels unfair… it takes the fun out of the game of avoiding speed traps.

7

You can tell which one is moving faster but 4 of the 5 were speeding. For that matter we all could have been speeding, I could have been the slowest speeder. I saw two flashes, do they take pics of all the cars or just an individual car?

When a speeding clump over takes you how do you know you won’t be included in with the ones speeding.

8

I was in MD. I had just paid a photo speeding ticket from a few weeks before.

I can’t remember if I had just gotten onto 29 off of 70, or onto 100 off of 29. It was late and normally I wouldn’t worry about speeding in a work zone, nobody is out working that late. Now when I see photo enforced I slow down.
I didn’t know if we would all get tickets, or if they can pick out the speeders.

9

I got a speed-camera ticket in DC. The ticket said that a ticket would be issued only if there were no cars within 100 feet of the subject car. The ticket showed two photos of my car with no other cars in the photo.

I do not know if this is due to a technical limitation of the equipment or whether it is to avoid challenges to the tickets. I also don’t know if this is typical of speed cameras. Or how it measures the speed.