Evaluating the Effects of Road Geometry, Environment, and Traffic Volume on Rollover Crashes

Abstract

There are a number of factors that cause motor vehicles to rollover. However, the impacts of roadway characteristics on rollover crashes have rarely been addressed in the literature. This study aims to apply a set of crash prediction models in order to estimate the number of rollovers as a function of road geometry, the environment, and traffic conditions. To this end, seven count-data models, including Poisson (PM), negative binomial (NB), heterogeneous negative binomial (HTNB), zero-inflated Poisson (ZIP), zero-inflated negative binomial (ZINB), hurdle Poisson (HP), and hurdle negative binomial (HNB) models, were developed and compared using crash data collected on 448 segments of Malaysian federal roads. The results showed that the HTNB was the best-fit model among the others to model the frequency of rollovers. The variables Light-Vehicle Traffic (LVT), horizontal curvature, access points, speed limit, and centreline median were positively associated with the crash frequency, while UnPaved Shoulder Width (UPSW) and Heavy-Vehicle Traffic (HVT) were found to have the opposite effect. The findings of this study suggest that rollovers could potentially be reduced by developing road safety countermeasures, such as access management of driveways, straightening sharp horizontal curves, widening shoulder width, better design of centreline medians, and posting lower speed limits and warning signs in areas with higher rollover tendency.

Crash Frequency Analysis Using Hurdle Models with Random Effects Considering Short-Term Panel Data

“…These results indicate that the presence of over-dispersion in the short-term crash data is due to both excess zeroes and unobserved heterogeneity. Without considering the random effect, most of the research [29,30,31,32] about crash frequency modeling using hurdle models found that hurdle negative binomial models are not convergent or not preferred. For example, Hosseinpour et al [30] have found that the hurdle Poisson model instead of the hurdle negative binomial model was the best one among different models being considered in terms of comparative measures.…”

“…As an alternative to zero-inflated models, hurdle models have some inherent advantages on model assumptions. By relaxing the structural zero assumption, hurdle models assume that all zeroes in the crash data are sampling zeroes [29,30,31,32]. In contrast to the structural zero assumption presuming an inherently safe condition with no crashes, sampling zero assumption implies that all segments have crash potential and the zero state does not remain permanently on any road segment [29,30,31,32].…”

“…By relaxing the structural zero assumption, hurdle models assume that all zeroes in the crash data are sampling zeroes [29,30,31,32]. In contrast to the structural zero assumption presuming an inherently safe condition with no crashes, sampling zero assumption implies that all segments have crash potential and the zero state does not remain permanently on any road segment [29,30,31,32]. Existing crash studies using hurdle models [29,30,31,32,33] were primarily developed based on cross-sectional data (as opposed to panel data) and did not consider random effects.…”

“…In contrast to the structural zero assumption presuming an inherently safe condition with no crashes, sampling zero assumption implies that all segments have crash potential and the zero state does not remain permanently on any road segment [29,30,31,32]. Existing crash studies using hurdle models [29,30,31,32,33] were primarily developed based on cross-sectional data (as opposed to panel data) and did not consider random effects. These studies ignore temporal and spatial correlations, which, however, are critical to short-term panel data.…”

Use of Remotely Piloted Aircraft Systems to Evaluate the Effects of Transport Collision

“…The most dangerous branch of transport is land transportation, including road and rail traffic [13]. It is this area of transportation where inter-vehicle collisions or collisions with fixed obstacles are the most frequent.…”