The Urban Dynamometer Driving Schedule is a mandated dynamometer test on tailpipe emissions of a car that represents city driving conditions. It is defined in 40 C.F.R. 86

It is also known as FTP-72 or LA-4, and it is also used in Sweden as the A10 or CVS (Constant Volume Sampler) cycle and in Australia as the ADR 27 (Australian Design Rules) cycle.
The cycle simulates an urban route of 12.07 km (7.5 mi) with frequent stops. The maximum speed is 91.2 km/h (56.7 mi/h) and the average speed is 31.5 km/h (19.6 mi/h).

The cycle has two phases: a "cold start" phase of 505 seconds over a projected distance of 5.78 km at 41.2 km/h average speed, and a "transient phase" of 864 seconds, for a total duration of 1369 seconds. The first two phases are run together as one large phase and followed by stopping the engine for 10 minutes, then restarting the engine to test warm restart, and re-running the first phase again (505 seconds) to make the complete 3 phase FTP-75 {July 2014}. In the U.S., weighting factors are applied to the emissions constituent numbers to add a correction for the frequency of how often a typical cycle would be performed in the real world. The first phase (cold start, 505 seconds) has a correction of 0.43 as cold starting is encountered less often. Phase 2 (864 seconds of city drive) has a weighting of 1.0, meaning the constituents in this area are counted full to stress the need for cleanliness in normal warmed-up drive, and the 0.57 is applied to the third phase (warm start, 505 seconds, repeat of phase one only with a warm engine start, which indicates that the real-world effect of warm starts happen more often than cold starts.

The "city" driving program of the EPA Federal Test Procedure is identical to the UDDS plus the first 505 seconds of an additional UDDS cycle
EPA FTP-75 driving cycle

Then the characteristics of the cycle are:

Distance travelled: 17.77 km (11.04 miles)
Duration: 1874 seconds
Average speed: 34.1 km/h (21.2 mph)

The procedure is updated by adding the "hot start" cycle that repeats the "cold start" cycle of the beginning. The average speed is thus different but the maximum speed remains the same as in the UDDS. The 10 minute pause is put at the end of transient phase before the hot start.[clarification needed] The weighting factors are 0.43 for the cold start, 1.0 for the transient phase and 0.57 for the hot start phase.[clarification needed]

Though it was originally created as a reference point for fossil fuelled vehicles, the UDDS and thus the FTP-75, are also used to estimate the range in distance travelled by an electric vehicle in a single charge.
Highway driving[edit]

EPA HWFET driving cycle

The "highway" program or Highway Fuel Economy Driving Schedule (HWFET) is defined in 40 C.F.R. 600 Appendix I.
It uses a warmed-up engine and makes no stops, averaging 48 mph (77 km/h) with a top speed of 60 mph (97 km/h) over a 10-mile (16 km) distance.

The following are some characteristic parameters of the cycle:

Duration: 765 seconds
Total distance: 10.26 miles (16.45 km)
Average Speed: 48.3 mi/h (77.7 km/h)

The measurements are adjusted downward by 10% (city) and 22% (highway) to more accurately reflect real-world results.[9]

Supplemental tests
In 2007, the EPA added three new Supplemental Federal Test Procedure (SFTP) tests[10] that combine the current city and highway cycles to reflect real world fuel economy more accurately,. Estimates are available for vehicles back to the 1985 model year.[5][11]

EPA US06 supplemental driving cycle

The US06 Supplemental Federal Test Procedure (SFTP) was developed to address the shortcomings with the FTP-75 test cycle in the representation of aggressive, high speed and/or high acceleration driving behavior, rapid speed fluctuations, and driving behavior following startup.

SFTP US06 is a high speed/quick acceleration loop that lasts 10 minutes, covers 8 miles (13 km), averages 48 mph (77 km/h) and reaches a top speed of 80 mph (130 km/h). Four stops are included, and brisk acceleration maximizes at a rate of 8.46 mph (13.62 km/h) per second. The engine begins warm and air conditioning is not used. Ambient temperature varies between 68 °F (20 °C) to 86 °F (30 °C).

The cycle represents an 8.01 mile (12.8 km) route with an average speed of 48.4 miles/h (77.9 km/h), maximum speed 80.3 miles/h (129.2 km/h), and a duration of 596 seconds.

Cold cycle
A cold temperature cycle uses the same parameters as the current city loop, except that ambient temperature is set to 20 °F (−7 °C).

EPA tests for fuel economy do not include electrical load tests beyond climate control, which may account for some of the discrepancy between EPA and real world fuel-efficiency. A 200 W electrical load can produce a 0.4 km/L (0.94 mpg) reduction in efficiency on the FTP 75 cycle test.[12]