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5.3.3 Roadway Characteristics

Compared to roads with speed limits <50km/h, occupants in two-vehicle angle crashes

involving heavy vehicles on roads with higher speed limits are more likely to experience
severe injury. This result was expected and is consistent with the findings of previous studies

(Chang & Mannering, 1999; Cerwick et al., 2014). Highways, freeways and main roads are
associated with less severe injury in two-vehicle angle crashes involving heavy vehicles.

These results were not surprising, because the reference case (Others) included tourist roads,
forest roads, and interchange ramps, which are more hazardous locations.

5.3.4 Temporal

Occupants are more likely to suffer severe injury if they are involved in crashes that occur at

night, but suffer less severe injury if the crashes occur during the morning peak hours. The

former result may be due to drivers’ fatigue and drowsiness, as well as higher vehicle speed,
which might contribute to severe injury at night, while less severe injury during the morning

peak may be due to the high traffic volume on the roads and vehicles being driven at lower
speed (Pahukula et al., 2015).

5.3.5 Other Collision Characteristics

In relation to police not attending crash sites, police presence at crash sites is more likely to

be associated with severe injury. Although police attendance at crash scenes would reduce

the likelihood of secondary collisions and provide basic emergency medical services, which
should reduce injury severity, police are also more likely to attend a crash scene if they

suspect that the crash may be severe.

5.4 Conclusions

The safety of occupants in crashes involving heavy vehicles has drawn considerable attention
from government agencies and the general public. Heavy vehicles have many unique

operating characteristics, such as poor deceleration and stopping capabilities, high rigidity,

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