Mark the intended route out on a road map. Pay particular attention to the parts of the highway where the speed limit changes or places where traffic can become congested. Designate each of these stretches of the highway as a separate segment.
Write down the posted speed limits and number of miles for each segment of your trip. If you are unsure of the speed limit on a particular portion of a highway, estimate it as 65 mph. Most highway speeds are between 55 mph and 70 mph, depending on the highway and what state you are driving in.
Calculate the number of minutes that it will take you to traverse each segment of your trip by using the following formula: Travel Time=Speed Limit x Distance / 60. In our example, the first segment would yield 55 x 20 / 60 = 18.3 minutes, and the second segment would calculate to 70 x 10 / 60 = 11.7 minutes.
Add the travel times of all segments together. The total time for our sample trip would be 18.3 + 11.7 = 30 minutes. Assuming that you never drive faster than the speed limit, this would be the shortest amount of time that your highway trip will require.
