Quantifying the contribution of low-level speeding to trauma in Victoria

Low-level speeding (driving at up to 10 km/h above the limit) is deemed to be the major contributor to speeding-related casualty crashes in Victoria. Understanding the size of the trauma problem that could be attributed to low level speeding is important for honing speed enforcement and public education strategies. In this study, we attempted to estimate the proportion of casualty crashes occurring on Victorian roads that could be attributed to low-level speeding. Almost 350,000 vehicle traveling speed recordings collected by covert mobile speed cameras across Melbourne Metro and regional Victoria, and within 40, 50, 60, 70, 80, 90, 100 and 110 km/h zones were compiled. The casualty crash risk formulae developed by Kloeden et al. (1997; 2001; 2002) were used to estimate the casualty risks associated with various levels of speeding. These risk levels were then combined with the survey speed data to estimate the size of the casualty problem due to low-level speeding. Vehicle traveling speeds showed that 9.5% of Victorian drivers violated the speed limit. Among these speeders, 94.9% were low-level speeders. Our analyses showed that 79% of speeding-related casualty crashes in Victoria could be ascribed to low-level speeding, while excessive speeding (21+ km/h above the limit) is likely to contribute to only 4.3% of speeding-related casualty crashes in Victoria. The results of this study justify the emphasis placed on low level speeding by the enforcement regime and public education campaigns. They also highlight the need to continue to raise the public awareness of the dramatic, cumulative consequences of low-level speeding in the community.