How are the white strips on the road used to determine speed?

Question

i know they time it from one point to another but what apparatus is used to do this? and/or what device is used?

Answer 1

A spotter with binoculars in an airplane or helicopter times how long it takes you to drive from one line to the other using either a stopwatch or a computer. Since the lines are a known distance apart, & since all speed means is "distance over time", you can calculate the speed.

For example-

X feet in Y seconds -> X/Y = Z ft/sec = __ miles/hr.

950 feet in 10 seconds -> 950/10 = 95 ft/sec = 65 miles/hr.

- David

Answer 2

By a system known as VASCAR, or a speed computer.  They are fairly uncommon since same direction radar is now more widely available.

Answer 3

They are not used to determine speed.  Speed is determined my radar - not white lines.

Answer 4

They are probably a known distance apart.  By timing how long it takes to drive between them you can calculate speed.

Answer 5

The lines that run perpindicular to the road are set at certain intervals and are used by helicopter patrols to determine speed. In theory satellites could also be used.

Answer 6

the lines are placed at a certain distance apart. Your vehicle is timed the moment your car crosses the first line until your car passes the second line. Your time is then calculated at that distance to result in your exact MPH. Some say this method is actually slightly more accurate and reliable then radar.

Answer 7

Those lines are used by aerial planes/choppers to time you between those 2 lines. . . distance/time == velocity, so if they see you going over the speed limit, they can radio ahead to a cruiser to pull you over, even though that cruiser never actually tagged you with radar.