Back to Annual Meeting Page		American Public Health Association 133rd Annual Meeting & Exposition December 10-14, 2005 Philadelphia, PA

Abstract #117334

Kavi Bhalla, PhD, Majid Ezzati, PhD, Ajay Mahal, PhD, Joshua Salomon, PhD, and Michael R. Reich, PhD. Harvard School of Public Health, Harvard University, 9 Bow Street, Harvard Center for Population and Development Studies, Cambridge, MA 02138, 6172337700, kavi_bhalla@harvard.edu

Purpose: We examine the relative roles of vehicle-prevalence and vehicle-type on traffic safety outcome as the number of motorized trips in a society increase.

Methods: We develop a risk-assessment based methodology that estimates traffic fatalities by computing the likelihood of a crash and the likelihood of a fatality in the event of a crash. Proportion of motorized trips and vehicle-type are the primary variables that determine crash and fatality risk. We use the methodology to predict the safety outcome (fatalities broken down by road-user type) with increasing motorization under the following scenarios of transportation growth: high bus usage, high car usage, high scooter usage, and a business-as-usual scenario.

Results: With increasing number of motorized trips, the model predicts that in every transportation scenario:

- Traffic fatalities first rise and then fall. However, traffic fatalities remain lowest for the bus-use dominated scenario and are highest for the scenario dominated by scooter use.

- Fatalities per vehicle always fall. However, the fall is steepest for the car-use dominated scenario and is least rapid for the scenario dominated by car use.

Conclusions: A rise in the use of motorized vehicles decreases the crash risk of an individual but increases the risk to others. The aggregate outcome of this effect is that as societies motorizes, the threat to non-occupants increases, causing traffic fatalities to rise. However, eventually the total number of non-occupants begins to fall resulting in a decrease in total fatalities. Since increasing motorization decreases the non-occupant population, fatalities per vehicle always fall.

Learning Objectives: At the conclusion of the session, the participant in this session will be able to

(
• Recognize the natural base-line trends in safety indicators and their relationship with historic data; and (
• Understand the role of motorization and vehicle-type in traffic safety trends. In addition, the participant will learn about an application of risk-assessment methodologies to road safety in developing countries.

Keywords: Injury Risk, Motor Vehicles

Presenting author's disclosure statement:

I wish to disclose that I have NO financial interests or other relationship with the manufactures of commercial products, suppliers of commercial services or commercial supporters.