The use of fuel economy data from the Federal Test Procedure (FTP) has provided a substantial amount of data on the fuel economy of passenger cars in urban driving conditions. Since the FTP does not represent the type of driving done in rural areas, especially on highways, a driving cycle to assess highway fuel economy was a desirable supplement to the FTP.
The new Environmental Protection Agency (EPA) “highway” cycle was constructed from actual speed-versus-time traces generated by an instrumented test car driven over a variety of nonurban roads and highways. This cycle reflects the correct proportion of operation on each of the four major types of nonurban roads and preserves the non-steady-state characteristics of real-world driving.
The average speed of the cycle is 48.2 mph and the cycle length is 10.2 miles, close to the average nonurban trip length.
Preliminary vehicle tests show that rotary and conventional engine-powered vehicles achieve approximately the same ratio of highway fuel economy to urban (FTP) fuel economy. Various unconventional engine-powered vehicles show different values for the ratio of highway to urban fuel economy. The continued use of the highway cycle will establish a data base which, when used in conjunction with FTP data, will allow better estimates of both fuel economy and exhaust emission trends.