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Emission Test Cycles

Heavy Heavy-Duty Diesel Truck (HHDDT) Schedule

Time-speed data points: Creep | Transient | Cruise

The Heavy Heavy-Duty Diesel Truck (HHDDT) schedule is a chassis dynamomter test developed by the California Air Resources Board with the cooperation of West Virginia University.

The test consists of four speed-time modes, including idle, creep (shown in Figure 1), transient (Figure 2) and (high speed) cruise (Figure 3).

Figure 1. HHDDT Creep Mode
Figure 2. HHDDT Transient Mode
Figure 3. HHDDT Cruise Mode

Selected statistics for the particular HHDDT modes are compared with those for the UDDS cycle in the following table.

Table 1
Statistics for HHDDT And UDDS Schedules
ParameterHHDDT CreepHHDDT TransientHHDDT CruiseUDDS
Duration, s25366820831063
Distance, mi0.1242.8523.15.55
Average Speed, mph1.7715.439.918.8
Max. Speed, mph8.2447.559.358
Max. Acceleration, mph/s2.
Max. Deceleration, mph/s-2.53-2.8-2.5-4.6
Total KE, mph23.66207.61036373.4
Percent Idle42.2916.38.033.4