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Speed Conversion

Helpful for Vascar to check if the speed you are charged with is correct

Conversion: Time Distance Speed Miles Per Hour To Feet Per Second

Miles per hour can be changed to feet per second by multiplying the number of miles per hour by the feet in a mile (5,280) and dividing by the seconds in an hour (3,600). This is approximately equivalent to multiplying miles per hour by 1.47 (which is 5,280 / 3,600 to two decimal places).

Mathematical Formula

v = 1.47s
v = velocity (feet per second)
s - speed (miles per hour)

Example
60mph = 5,280 / 3,600 = 88 ft per sec exactly or
60mph = 60 x 1.47 = 88.2 feet per second approximately
Rough estimates: miles per hour can be multiplied by 1.5
Put another way, half the number is added to the number

Example
60mph = 60 x 1.5 = 90 ft per see, approximately or
60 mph plus 30 mph (half that amount) = 90 ft per sec, approximately

Conversion: Time Distance Speed Miles Per Hour To Feet Per Second

Example
60mph = 60 x 1.5 = 90 ft per see, approximately or
60 mph plus 30 mph (half that amount) = 90 ft per sec, approximately

Conversion: Velocity to Speed Feet Per Second To Miles Per Hour

Feet per second can be changed to miles per hour by multiplying by the seconds in an hour (3,600) and dividing by the feet in a mile (5,280). This is approximately equivalent to dividing by 1.47 or multiplying by 0.682 (3,600 / 5,280 to three decimal places)

Mathematical Formula

s = v / 1.47 or s = 0.682v
v = velocity (feet per second)
s - speed (miles per hour)

Example
66 ft per sec = 66 x 3,600 / 5,280 = 45 mph exactly or
66 feet per second = 66 x 0.682 = 45.0 mph approximately
Rough estimates: miles per hour is two thirds of feet per second

Example
two thirds of 66 feet per second is 44 miles per hour approximately or
66 feet per second = 66 x 2 = 132 / 3 = 44.0 mph approximately
66 feet per second = 66 x 0.682 = 45.0 mph approximately
Multiplying by 2/3 (0.6667) is roughly the same as dividing by 1.5

Example
66 feet per second = 66 / 1.5 44.0 mph approximately

VISUAL ESTIMATE

As a part of radar or vascar training in most States, officers must make visual estimates of speed. To become certified and receive a wallet certification card, each must accurately estimate speeds: (since this changes on occasion you should check with you highway department or in the State Statutes to see what your State requires)

On the sit" 10 estimates plus or minus 3 miles per hour
On the move" 5 estimates plus or minus 5 miles per hour

To quote the TV credit card commercial: "What's in your wallet?"
Hopefully, the officer doesn't possess the certification card. If he doesn't, ask for dismissal.