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Difficulties with Quasi-Induced Exposrue when Speed Varies Systematically by Vehicle Type

Product Type

Journal Article

Author

Jiang, X. and R.W. Lyles

Date

Jul-07

Full citation

Jiang, X. and R.W. Lyles. Difficulties with Quasi-Induced Exposrue when Speed Varies Systematically by Vehicle Type. In Accident Analysis and Prevention, Vol. 39, No. 4, Pergamon Press, Oxford, NY, July 2007, pp. 649-656

Abstract

The attractiveness of quasi-induced exposure lies in the simplistic nature of its theory and application. As opposed to vehicle miles of travel, quasi-induced exposure is developed solely from the accident data themselves. Involvement ratios (IRs) are used to describe the relative over- or under-involvement of different drivervehicle combinations in traffic accidents. The issue of systematic bias in the involvement ratios is explored, and it is shown both theoretically and empirically that the variation in average speeds between vehicle types can affect relative accident involvement ratios. For vehicle types that routinely travel faster, the IRs will likely be underestimated; while for slower-moving vehicle types, the IRs will be overestimated. In the case of speed, the magnitude of the effect on the IRs is dependent both on the magnitude of the speed differential and the percentage of slower vehicles in the traffic stream. Conclusions can be extended to whenever there are speed or other behavior disparities associated with the drivervehicle combinations in the traffic stream. Other examples include the speed discrepancy caused by different drivers (e.g., younger versus older drivers). Caution must be used in interpreting results from applications of the quasi-induced technique whenever such biases might be encountered.

Available From

Accident Analysis and Prevention

Link To Journal Article

Difficulties with Quasi-Induced Exposrue when Speed Varies Systematically by Vehicle Type

Keywords

Accident analysis
Accident data
Accident exposure
Accident rates
Motor vehicles
Speed
Traffic accidents
Vehicle characteristics
Vehicles by speed


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