The objectives of this research were (1) to identify the key geometric characteristics and combinations of characteristics of road and street designs that affect accident frequencies and severity; (2) to quantify the effects of varying the key characteristics and combinations of characteristics on accident frequencies and severity; and (3) to develop a methodology that can be used by engineers in measuring the cost effectiveness of the various levels of each design element. Because only a limited number of design elements could be studied in-depth during this research, the features of pavement width, shoulder width, and shoulder surface type for rural two-lane highways were selected for quantifying their relationship to accident frequencies and severity. No significant difference was found in the accident rate between 22-ft and 24-ft pavement widths. There was a measurable difference between the 18-, 20-, and 22-ft pavements, with the wider pavements having lower accident rates. Wider shoulders and paved shoulders were also found to have lower accident rates. A cost-safety-effectiveness methodology was developed to incorporate the quantified relationships into a practical design procedure. (Author/publisher)
Samenvatting