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]](images/hhddt-creep.png)
Figure 1. HHDDT Creep Mode
![[chart]](images/hhddt-trans.png)
Figure 2. HHDDT Transient Mode
![[chart]](images/hhddt-cruz.png)
Figure 3. HHDDT Cruise Mode
Selected statistics for the particular HHDDT modes are compared with those for the UDDS cycle in the following table.
| 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 |