Safety Effects of Cross-Section Design for Two-Lane Roads. Volume 2. Appendixes

摘要

The study was intended to quantify the benefits and costs resulting from lane widening, shoulder widening, shoulder surfacing, sideslope flattening, and roadside improvements. Detailed traffic, accident, and roadway data were collected on 4,951 miles of two-lane roads in seven States. An accident predictive model and statistical tests were used to determine expected accident reductions related to various geometric improvements. Factors found to be most related to reduced accidents were wider lanes and shoulders, improved roadside conditions, and flatter sideslopes. Paved shoulders were found to have a marginal safety benefit compared to unpaved shoulders. Detailed accident analyses were also conducted for roadside features. The volume contains appendixes to the final report. Appendixes are included on the development of the scale used to rate the roadside hazard, the statistical breakdown of key variables, the severity of different types of run-off-road accidents and the development of the cost estimates for cross-section improvements.