Average speed indicates how fast a vehicle travels over a specific distance in a certain amount of time. This contrasts with instantaneous speed, which reveals how fast a vehicle is traveling at a particular moment.
Average speed is the ratio of distance traveled to time spent. To find average speed, divide the total number of miles traveled by the total elapsed time in hours. The answer is the average speed in miles per hour. For example, imagine a car traveled 90 miles in 1 1/2 hours. To determine the average speed, divide 90 by 1.5. The answer is 60 mph.