How do traffic department personnel detect a car going over speed limit ? [I Obey the Speed Limit]

What sensors do they use ?

And if anybody knows what data the sensors gather and how they calculate instantaneous speed, that would be great too ?

Or do they use a pair of sensor located close to each other ? That would make it easier. IDK

This is NOT a homework question, BTW

And most importantly, can bluetooth sensors be used to do that?

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Roadsterrider · 56-60, M

It depends on the agency, some use radar, some use lasers. Some use time, ever drive across a white line painted on the road and then there would be another line a few 100 meters down the road? An officer in an aircraft will start a stopwatch when a car crosses the first line and again when it goes across the 2nd line. Doing the speed limit, it takes 4 seconds to travel between the lines, if you travel between them in 3 seconds, you are exceeding the speed limit. Laser and radar both work the same way, a beam of radar or light, at a certain frequency, goes out and bounces back from the target, the changing frequency tell how fast the target is approaching.

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Roadsterrider · 56-60, M

@MasterofNone No, I have no idea how that would be used to determine speed with the exception of some kind of GPS input or calculation.

MasterofNone · 26-30, M

@Roadsterrider What I know about bluetooth sensors is that they take in data from the bluetooth devices inside a car to identify it or the person inside it. Then another bluetooth sensor on another location will do that again. The time it took the car to travel from one bluetooth sensor to another could be used to calculate average speed. But calculating average speed instead of instantaneous doesn't sound very useful.

Roadsterrider · 56-60, M

@MasterofNone I don't care if they monitor speed or not, my biggest problem with blue tooth is that it is basically a surveillance system we are almost forced to use. Some states have talked about a "use tax" for highways based on how much you drive. The data is there, it just has to be sorted. The government doesn't need to know where I am 24-7 and they have no right to collect that data. Please excuse me while I go put my tinfoil hat back on.

Elevatorpitches · F

electronic sensors on the traffic light apparatus, and many other places.

MasterofNone · 26-30, M

@Elevatorpitches Yes! But which electronic sensors ?

Elevatorpitches · F

@MasterofNone I don't know, I just know they are there and they do catch speeders and on the lights everyone is stopped so who knows how they work... I think they are all over the place on the roads...

Pfuzylogic · M

They don’t need sensors.
It is Doppler principles used in radar.

MasterofNone · 26-30, M

@Pfuzylogic Ah good. Makes sense.

I actually had data on vehicles from bluetooth sensors and was wondering if there was a way to find out instantaneous speeds of various vehicles from it.

Pfuzylogic · M

@MasterofNone
Doppler has a shift in frequency dependent on speed.

iamnikki · 31-35, F

It's not important if one simply obeys speed limit

MasterofNone · 26-30, M

@iamnikki It is, if you want to catch those who are not.

iamnikki · 31-35, F

@MasterofNone if this is a part of your job, shouldn't you already be informed of the workings? Seems like a weird question 🤷‍♀️ hope you find your answer

MasterofNone · 26-30, M

@iamnikki It is not a part of my [i]job[/i]. Should you only do that which is your job ?🤦‍♂️

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