Tire rolling resistance information is generally obtained in the laboratory by use of the rotating drum technique. Coast-down tests of road vehicles, when properly carried out, will relate laboratory-measured tire rolling resistance to the rolling resistance that exists under actual operating conditions. Also, these road tests can be used to compare the rolling resistances of several sets of tires. This paper describes the procedures that must be followed and the limitations that exist in the determination of tire rolling resistance from coast-down tests. The results of one such test are used as an example of the method.