Citation

Himes S, Porter RJ, Eccles K. Transp. Res. Rec. 2018; 2672(39): 11-19.

Copyright

(Copyright © 2018, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.1177/0361198118783162

PMID

unavailable

Abstract

A Policy on Geometric Design of Highways and Streets, 6thEdition, (publisher: AASHTO), provides design criteria for minimum sight distances, including intersection sight distance (ISD). An understanding of the relationship between ISD and safety at stop-controlled intersections is needed, with potential applications of this knowledge to both performance-based design and substantive road safety management practices. To establish this relationship, crash, traffic, and geometric data were collected from 832 two-lane minor unsignalized intersection approaches in Ohio, and Washington. The data were analyzed using a cross-sectional study design to quantify the relationship between safety and ISD. The analyses indicated that the expected number of target crashes are associated with available ISD. Target crash frequencies increase as available ISD decreases.

RESULTS suggest that ISD is associated with expected crash frequency in a non-linear fashion. The sensitivity of the expected number of target crashes to changes in ISD is highest when ISD is shorter, and decreases as ISD increases (i.e., the safety benefit of increasing ISD from 300 to 600 ft is substantially larger than the safety benefit of increasing ISD from 1,000 to 1,300 ft). The results also suggest that the impacts of ISD on crash frequencies vary as a function of the major road two-way annual average daily traffic and the major road speed limit. The sensitivity of the expected number of crashes to changes in ISD increases as both traffic volume and speed limit increase. Crash modification functions for each of the target crash types were estimated using the regression models.

Language: en