Roadside Fixed-Object Collisions, Barrier Performance, and Fatal Injuries in Single-Vehicle, Run-Off-Road Crashes

Abstract

Objectives: To quantify the odds of fatal injuries associated with drivers involved in single-vehicle, run-off-road (SVROR), injury crashes. Methods: An in-service safety evaluation was carried out using multivariate logistic regression models. Results: The odds of motorist death was lower for w-beam guardrail crashes as compared to tree, pole, and concrete barrier crashes. On the other hand, there was no statistically significant difference between the odds of motorist death in concrete barrier crashes as compared to tree or pole crashes. The odds of motorist death were lower for curbs and collision-free crashes as compared to tree, pole, and barrier crashes. Thus, obstacles should be removed whenever possible and barriers installed only whenever absolutely necessary. The lack of vehicle containment (in barrier crashes) was found: (i) to tend to occur on higher-posted-speed-limit roads and result in a higher percentage of fatal crashes, (ii) to be more prevalent with the less rigid barrier type, and (iii) to result in a consistently higher percentage of fatal crashes under the concrete barrier category. Conclusions: Findings not only support state-of-the-art roadside design guidelines and crash-testing criteria, but they may also be useful in evaluating proposed roadside safety improvements.

Impact of Roadside Design Compliance and Hazard Offset on the Risk of Single-Vehicle, Run-Off-Road Crash Fatalities

“…The first model included all SVROR-injury crashes, the second model excluded free-collision events, and the last model excluded not only free-collision events but also curb crashes. The findings from a previous study, based on the same dataset used in the present research, found that collision-free events and curb crashes tend to be less severe than tree/pole/barrier crashes (Albuquerque & Awadalla, 2020a). Thus, excluding collision-free events and curb crashes is important in order to more accurately quantify the impact that HLO may have on crash severity.…”

“…Thus, excluding collision-free events and curb crashes is important in order to more accurately quantify the impact that HLO may have on crash severity. Furthermore, barrier crashes were also excluded from the data used in the models shown in Table 5, as previous research using the same dataset used in the present research showed that w-guardrail crashes are less severe than tree/ pole crashes (Albuquerque & Awadalla, 2020a). This is also relevant because CZ width policy aims at addressing locations with hazards such as trees and poles instead of barriers.…”

“…Hence, the logit model was used (Agresti, 2018). The logit model has been adopted in similar road-safety-related studies in the past (Albuquerque & Awadalla, 2020a;Russo & Savolainen, 2018;Zou et al, 2014) and the fact that its outputs may be easily interpreted in terms of odds ratio was a deciding factor for using this model in this study. The binary logistic regression model can be expressed as shown in Equation 1, which gives the logit mean of the probability of the response variable as a function of a k number of explanatory variables.…”

“…Thus, it may be relevant to investigate the impact of some of these specific reasons on fatality risk. The impact of hazard shielding on the odds of fatal injury occurrence were investigated by a previously conducted study based on the same dataset used in the present study (Albuquerque & Awadalla, 2020a). The impact of HLO, TLHLO, and TLBLO on fatality risk is described in the following sections.…”

Benchmark Compliance Evaluation of the Roadside Design in an Urban, High-Density Area

“…This study found that 65% of the crash sites investigated warranted a barrier but one was not installed, while 80% (see Table 5) of all crash sites investigated did not meet roadside design guidelines for barrier placement. This is relevant considering that past research has shown that the odds of fatal injuries occurring in pole and tree crashes are significantly higher than the odds of fatal injuries occurring in guardrail crashes [36].…”