Developing a database of rockfall-vehicle impacts to evaluate human vulnerability along transportation routes

Abstract

Rockfall poses a widespread hazard along roads below steep slopes and affects the safety of roadway users. When vehicles are impacted by falling rock, occupants may sustain major injuries or be killed. However, low- or no-consequence rockfall impacts also occur and these are particularly important when evaluating the statistical vulnerability of people in vehicles struck by falling rock. Here, we examine more than 50 case studies from publicly available data sources (e.g., published literature, news reports) that document rockfalls with a confirmed vehicle impact. Using these resources, we record detailed site conditions (e.g., sourced from a roadcut or cliff, cause), rockfall metrics (e.g., volume, fall height), and vehicle characteristics (e.g., type, occupancy, travel direction) and compile that information into a database. These data provide a mechanism to evaluate relationships between hazard and risk through testing and development of vulnerability metrics. For example, from the site-specific event rockfall geometry characteristics (block size and fall height), the calculation of the potential energy of impacting blocks can be determined and compared with reported vulnerability outcomes. Additional statistical analysis can then be used to quantify the risk to people travelling along roadways and assess the likelihood of outcomes given site and vehicle characteristics. To develop statistically rigorous relationships, additional case studies are needed to develop an expanded database. Thus, this work highlights the benefit of preserving both the source area characteristics and the resultant human vulnerability outcomes in the wake of rockfall incidents to inform future risk assessments. These data and associated analyses can be used to assist transportation and land management agencies with risk assessment and decision making along rockfall-prone transportation corridors.