Rural two-lane highways constitute a majority of the mileage of public roads in the United States. Rural two-lane highways have 40% of the total travel but experience 60% of the highway fatalities. During the 1980's and 1990's, research was carried out in the United States to quantify the safety and operational effects of various key geometric design features including: lane and shoulder widths; roadside safety; horizontal and vertical alignment; sight distance; rural intersections. Aggregating this research has resulted in a compendium of the safety benefits of certain geometric design features for two-lane rural highways which links design standards and safety. This aggregated research information provides a basis for software analysis of proposed highway designs to assess their expected safety performance as well as the traditional capacity performance. Application of these benefits and effects achieves a numerical methodology for safety in a similar manner as is commonly carried out for capacity. This compendium of the safety and operational benefits of highway design features is being deployed in the United States to state highway departments in advance of the release of the software based analysis system. For the covering abstract of this conference see ITRD number E211395.

National statistics indicate that fatality rates on rural Federal-aid primary highways have been significantly higher compared to those for urban and rural Interstate highways and urban primary highways. Although this group of highways includes two-lane rural roads, an important component of the rural Federal-aid primary highways are multilane rural highways. More than 56 000 km of arterial highways in the United States are multilane, non-Interstate roads in rural areas. Many previous studies have been conducted regarding the safety effects of various traffic and geometric roadway features. The majority of these studies were concentrated on rural two-lane roads. There have also been a few notable studies that investigated roadway crosssection design elements for suburban highways and urban streets. However, there has been limited research on the safety effects of geometric design features on rural, multilane, nonfreeway highways. This study examined the effects of various cross-section-related design elements on accident frequency and developed an accident prediction model for rural, multilane, nonfreeway highways.