Browsing by Author "Davuluri, Sujay"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item A Case Control Study of Speed and Crash Risk, Technical Report 3: Speed as a Risk Factor in Run-off Road Crashes(2006-04-01) Davis, Gary A.; Davuluri, Sujay; Pei, Jian PingIn the U.S.A., the imposition and subsequent repeal of the 55 mph speed limit has led to an increasingly energetic debate concerning the relationship between speed and the risk of being in a (fatal) crash. In addition, research done in the 1960s and 1970s suggested that crash risk is a U-shaped function of speed, with risk increasing as one travels both faster and slower than what is average on a road. Debate continues as to the causes of this relationship, and there is reason to suspect that it may be an artifact of measurement error and/or mixing of different crash types. This report first describes two case-control analyses of run-off road crashes, one using data collected in Adelaide, Australia and the other using data from Minnesota. In both analyses the speeds of the case vehicles were estimated using accident reconstruction techniques while the speeds of the controls were measured for vehicles traveling the crash site under similar conditions. Bayesian relative risk regression was used to relate speed to crash risk, and uncertainty in the case speeds was accounted for by treating these as additional unknowns with informative priors. Neither data set supported the existence of a U-shaped relationship, although crash risk clearly tended to increase as speed increased. The resulting logit model was then used to estimate the probability that a given speed could be considered a casual factor for each of the 10 Minnesota crashes.Item Development and Testing of a Vehicle/Pedestrian Collision Model for Neighborhood Traffic Control(2002-02-01) Davis, Gary A.; Sanderson, Kate; Davuluri, SujayThis report presents an approach to assess the effect of vehicle traffic volumes and speeds on pedestrian safety. It shows that the probability of standardized pedestrian conflict resulting in a collision can be computed given data on the distribution of vehicle speeds and headways on a residential street. Researchers applied this method to data collected on a sample of 25 residential streets in the Twin Cities and found that collision rates varied between four and 64 collisions per 1,000 pedestrian conflicts, depending primarily on the street's traffic volume. Using a model that relates the impact speed of a vehicle to the severity of pedestrian injury, they computed the probabilities of a severe collision. Sensitive to both traffic volume and traffic speed, the severe collision rate varied between one and 25 collisions between 1,000 conflicts. Using the same data, researchers also computed the crash reduction factor, used to assess the potential safety effect of a 25 miles per hour speed limit on the sample of residential streets. The estimated crash reductions ranged between .2 and 45 percent, depending primarily on the degree to which the vehicle speeds currently exceeded 25 miles per hour. Researchers also showed how this computation assists with the reconstruction of actual vehicle/pedestrian collisions.