Roadway Departure Safety: A Manual for Local Rural Road Owners

7. Summary

Roadway departure crashes account for 53 percent of national fatalities, many of which occur in rural, local areas. Local administrators, township managers, and public works officials who maintain and operate local rural roads need to be engaged in roadway safety by reviewing understandable literature to guide their identification of roadway segments with safety issues and the countermeasures to address them.

To date, several States have completed Roadway Departure Safety Implementation Plans with assistance from FHWA. These plans were developed to guide roadway departure safety implementation activities on State and local roads arising from the State Strategic Highway Safety Plans. The implementation plans include the activities, countermeasures, strategies, deployment levels, implementation steps, and estimate of funds necessary to achieve the State's roadway departure safety goals. The local road practitioners should consult their State's Roadway Departure Safety Implementation Plan, if available, before embarking on an improvement strategy.

When seeking to address local rural road safety, the local practitioners should consider which implementation approach to institute. The three main approaches are – Systematic, Spot location, and Comprehensive. Availability and quality of crash and roadway data, number of locations to be addressed, and funding are factors that may play a role in the selection of an implementation approach.

Determining the nature of the problems and their locations will assist in making the most informed decisions for countermeasure selection and implementation in addressing roadway departure safety issues. When conducting a safety analysis, a minimum of 3 years of data is desired to obtain an accurate picture of the crash history within a jurisdiction, since crashes are relatively rare events and are not universally distributed across the system. Due to the possibility of changes in traffic patterns and the roadway itself, data more than 5 years old are typically not desirable for assessing the safety issues.

Analysis can range from simple "push pin" maps for identifying crash clusters to statistical analyses of crash rates, depending on the crash history and other available data. There are a number of information sources that can be used to identify crashes – State and local crash databases, law enforcement crash reports and citations, observational information from road maintenance crews and law enforcement, and public notification of safety concerns. Other variables to be considered when conducting analysis include crash location, date and time, crash type, crash severity, weather conditions, sequence of events, and contributing circumstances. In addition, roadway data and traffic volumes are factors to be considered when determining the roadway departure safety issues.

Regardless of the implementation approach chosen, a field review should be conducted at identified locations. Field reviews have the potential to identify safety issues and solutions that cannot be determined by data analysis alone. These reviews can be conducted as informal field reviews or as formal Road Safety Audits (RSAs).

Decisions regarding which countermeasures to install to address a safety issue can be challenging. When appropriate, the local practitioner should seek engineering expertise from a State or local engineer or through the State Local Technical Assistance Program (LTAP). For conventional rural roadway segments, warning signs, curve delineation, rumble strips, and fixed object removal should be considered. In addition, a large number of supplemental countermeasures are available for deployment based on crash history, location, and level of effectiveness.

Countermeasure assessment after implementation is important to the roadway departure safety program. This will inform the practitioner of the effectiveness of the strategy and if it should be applied to other locations. The most common methodology for the evaluation of a given countermeasure is the analysis of crash data before and after its installation. Three years of data after the installation is ideal for evaluation; however, changes in traffic volume and roadway information can also affect the outcome, so they should be taken into account during assessment.

While the challenge to decrease the number of roadway crashes on local rural roads may seem overwhelming due to limited resources, there are a number of low cost proven countermeasures that can be installed; many can be installed relatively quickly.

Local highway agencies have unique responsibilities and challenges related to the safety of their roadway system. By beginning any traffic safety effort using a data-supported approach, those agencies will be in a better position to address their highway safety needs.