The goal of this work is to investigate driver car-following patterns on freeways, particularly as a function of traffic flow level, using a headway distribution model. A number of authors have developed “two-component” vehicular headway distribution models that assume vehicles on a road can be divided into two groups according to whether or not they are interacting with the vehicle ahead. A model of this type, the “semi-Poisson” model proposed by Buckley, is applied to a data base consisting of 42,000 observed headways from a single lane of an urban freeway over a range of flow from 900 to 2,000 vehicles per lane per hour. A previously developed computational method allows the distribution of followers headways to be calculated directly from the observed total headway distribution by numerically solving an integral equation without introducing a parametric form for the followers distribution. The resulting followers headway distribution is found to be independent of the flow with a mean of 1.32 s and a standard deviation of 0.52 s. No statistically significant discrepancies are found between the model results and the observed data. The theoretical basis for the semi-Poisson model is discussed and compared with those of other models in order to assess the plausibility of the interpretation with respect to car following.
The danger compensation principle contends that the use of such vehicle safety features as seat belts may induce drivers to take greater risks. To test for this hypothesized effect, observational data on seat belt usage and driver risk taking were collected on 4812 drivers in Ontario, Canada, where seat belt usage is required by law. The hypothesized effect would result in higher risks taken by drivers compelled to wear seat belts, as indicated by closer following in freeway driving. Such an effect was sought by observing the difference between user and nonuser following headways and comparing it with a corresponding difference previously reported for Michigan, which has no mandatory usage law. The comparison provided no evidence of danger compensation behavior in car following. It was therefore concluded that this study presents no evidence that the safety benefits of seat belts would be diminished or neutralized by greater driver risk taking.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.