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).

[chart] — **Figure 1**. HHDDT Creep 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
Parameter	HHDDT Creep	HHDDT Transient	HHDDT Cruise	UDDS
Duration, s	253	668	2083	1063
Distance, mi	0.124	2.85	23.1	5.55
Average Speed, mph	1.77	15.4	39.9	18.8
Stops/Mile	24.17	1.8	0.26	2.52
Max. Speed, mph	8.24	47.5	59.3	58
Max. Acceleration, mph/s	2.3	3.0	2.3	4.4
Max. Deceleration, mph/s	-2.53	-2.8	-2.5	-4.6
Total KE, mph²	3.66	207.6	1036	373.4
Percent Idle	42.29	16.3	8.0	33.4