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Highlights • We modeled the distance traveled by an errant vehicle in a ROR crash. • Two Cox mixed-effects regression models were developed. • Results confirmed the contribution of roadside obstacles to the distance travelled. • Results suggest that clear-zone distances proposed in guidelines should be evaluated. • This study can facilitate the appropriate planning and design of forgiving roadsides. Abstract Roadway departure (RwD) crashes, comprising run-off-road (ROR) and cross-median/centerline head-on collisions, are one of the most lethal crash types. Nationwide, from 2014 to 2016, annual RwD crashes accounted for 53% of all motor vehicle traffic fatalities. Several factors may cause a driver leave the travel lane, including an avoidance maneuver and inattention or fatigue. Roadway and roadside geometric design features (e.g., lane widths and clear zones) play a significant role in whether human error results in a crash. In this paper, we present a hazard-based duration model to investigate the distance traveled by an errant vehicle in a run-off-road crash, the stopping hazard rates, and associated risk factors. For this study, we obtained five years' (2010–2014) of crash data related to roadway departures (i.e., overturn and fixed-object crashes) from the Federal Highway Administration's Highway Safety Information System Database. The results indicate that over 50% of the observed vehicles traveled no more than 36 ft. in a ROR crash and 25% of the observed vehicles traveled at least 78 ft. We also found that seasonal, roadway, and crash variables, along with vehicle information and driver characteristics significantly contributed to the distances traveled by errant vehicles in ROR crashes. This paper presents methodological empirical evidence that the Cox proportional-hazards model is appropriate for investigating the distances traveled by errant vehicles in ROR crashes. In addition, it also provides valuable information for traffic design and management agencies to improve roadside design policies and implementing appropriately forgiving roadsides for errant vehicles. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study the contributors influencing ran-off-road (ROR) crash severities in a setting that has not been analysed in the literature, namely on freeways not designed according to the “ forgiving roadside ” concept. To accomplish the analysis, ROR crash data were collected on freeway road sections in Portugal and multinomial and mixed logit models were estimated using the driver injury and the most severely injured occupant as outcome variables. Our results are in line with previous findings reported in the literature on ROR crash severity in a number of distinct settings. Most importantly, this study shows the contribution of critical slopes and vehicle rollover towards fatal injuries and highlights the importance of introducing the “ forgiving roadside ” concept to mitigate ROR crash severity in Portuguese freeways. The study also indicates the importance of protecting errant vehicles particularly in horizontal curves, as these are linked with fatalities. Finally, the empirical findings from the developed models revealed problems in current Portuguese roadside design, especially with regards to criteria for forgiving slopes provision and warrants for safety barrier installation. [ABSTRACT FROM AUTHOR]

Collisions with dangerous roadside obstacles and rollovers are responsible for many injuries and deaths in highways worldwide. International crash data indicate that roadside characteristics contribute to more than half of all run-off-road injury crashes (RORIC) involving serious injury or death. Furthermore, roadside geometric characteristics are believed to be the leading cause of rollover in single-vehicle RORIC. Differences in each country’s road network features, car vehicle stock, driving behavior, characteristics of roadside obstacles and economical aspects justify the need for evaluating the merit of specific approaches to roadside safety issues. Results from recent studies carried out at the Laboratório Nacional de Engenharia Civil – LNEC have shown that important differences exist between RORIC in Portuguese roads, when they are compared with RORIC in roads from other countries. A framework was developed for assisting in cost-effective decisions as regards roadside safety interventions, which is based on results from the analysis of registered data and the observation of inservice performance of installed equipments on Portuguese roads. A brief description is provided of cost–benefit analysis software tools for safety evaluation and simulation of roadside scenarios, which were developed at LNEC under a dedicated research project – SAFESIDE-roadside safety. The software contains a list of roadside safety measures (including the present value of their implementation costs and their safety effects) and an accident categorization (based on predictive models for crash frequencies and crash costs). The software is being disseminated by road authorities and relevant technical stakeholders, within the current revision of Portuguese road design standards. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model crash frequency in run-off-the-road injury crashes. [•] Different functional forms relating crash frequency and traffic flow are analyzed. [•] Run-off-the-road crashes should be modelled with a modified Ricker model. [ABSTRACT FROM AUTHOR]