How do police officers "clock" vehicle speed?

Question

Without pacing, the use of radar, Vascar etc. can an officer "accurately" judge the speed of a vehicle. If you know the formula please explain.

Member since: March 06, 2006
Total points: 889 (Level 2)
Points earned this week:
--% Best answer

Beej
S How do police officers "clock" vehicle speed?
Without pacing, the use of radar, Vascar etc. can an officer "accurately" judge the speed of a vehicle. If you know the formula please explain but remember:

a) 1000 ft. is NOT 1/4 mile.
b) in most areas speeding is a misdemeanor and a trial is not an entitlement.

Answer 1

It's called "point to point". We still did this when I first started on our department. Involves the time it takes for a vehicle to travel from point A to point B. Done with very accurate stop watch. It's actually pretty accurate but much more time consuming so everyone has gone to the more modern modes. Plus, as others have said, it's not hard to see a car flying by and deduce he is speeding. Many states have laws for " speeding over the posted limit" without proving actual speed or " too fast for conditions" which does not require a speed.

Will it "fly" in court? Who knows.

Answer 2

Yes - an officer can accurately judge the speed of vehicles witouty radar, etc...

As part of the radar certification (at least, in California), I was required to estimate the speeds of 100 vehicles within 5 mph of their actual speed. This is necessary as radar is used only to confirm the officer's estimate of speed.

It's not that difficult - it just takes practice.

Also, in many states, it's illegal for an officer to time a vehicle between two stationary points. That will give only an average speed over that distance - not an accurate definitive speed at a point in time. For those states where it is allowed, you just divide the distance traveled by the amount of time it took to travel that distance (also allowing for conversions of feet to miles and seconds to hours).

Calif Deputy

Answer 3

a white line is painted across the highway
at the moment you pass that line a stop watch is put into motion. another white line is ahead.as soon as you pass by it, the stop watch is halted. a comparison is made between the time you took to pass between the lines with a predetermined chart in the officers cruiser. If it is determined you are over the speed limit the officer has 2 options...you can be stopped immediately or trailed for a while to verify your speed. Then the officer can either give out a verbal or written warning,OR write out a citation,OR write a court summons,depending on the seriousness of the offense and the driver attitude/sobriety. Drivers in excess of 100 miles per hour can be arrested for reckless driving.

Answer 4

Here's a way to very roughly estimate speed: if you know the distance between two landmarks (say two street signs) you count the seconds it takes to get from one to the other. If it's 1000ft, it'll take roughly 15 seconds at 60mph. This is just an estimate, but it's a method of "clocking". If an officer didn't use pacing or radar, it will not hold up in court.

Answer 5

The formula is "wow, that vehicle is hauling". That is enough to stop a car. A reasonable person to can tell if a vehicle is going much much faster then the pack.

As for accurately judge, you can use a stop watch, distance divided by time. But it's a hassle and takes too long

Answer 6

They drive up near you, cruise at your same speed, make a note of it 'clock you' and then tell you when stopped. There's also other methods such as starting a special timer when you cross a road tick mark, then stop it when you cross the next one. The 'clock' then calculates it for them automatically. Spiffy!