Ever hear of this speed detection system used by cops?

[HotRoddin]

Originally posted by 82 GT
It's still prone to human error. The officer has to manually push a button to start the timer and also to stop it which means human error is introduced twice.

You're right, and the closer the 2 points he's measuring are together, the bigger the error if he's not right on pushing the button. lets say his measured distance is 600 feet (2 football field lengths), and lets say you actually took 6 seconds to go that distance ... that would be 68 MPH ... now lets say he pushes his stopwatch button a half a second early and times you at 5.5 seconds instead of the 6 it actually took you ... that means when you were actually going 68 MPH, his gizmo will say you're going 74 MPH. Now if hes timing you over a distance of say a mile like 95mustanggt was talking about then that same half second error in him pushing his button would only mean a difference of about 1 MPH ... so if you were actually going that same 68 MPH he'd clock you at 69 MPH. The error does increase as your speed increases too.
Keep in mind thats exactally how they get your speed at the drag strip... they have 2 timing lights a known distance apart and they time how long it took you to go that known distance, and convert it to MPH, but keep in mind these are electronic timers that time down to about a thousandth of a sec acurately, so they are very close to on the money.
Bottom line is you better hope they are timing you over a long distance or they are paying very close attention to when they push the button on that stopwatch (as opposed to picking the krispy Kreme glaze off their shirt)
To all you coppers on the board, the krispy kreme crack was just a joke !!! i swear it was !!