Study Details

Study Title: Examining Safety on Two-Lane and Multilane Highways in Consideration of Access Spacing

Authors: Hamzeie et al.

Publication Date:JAN, 2019

Abstract: Access management strategies, such as the introduction of minimum access point spacing criteria and turning movement restrictions have been shown to be important elements in optimizing the operational and safety performance of roadway segments. The relationship between safety and these types of access policies is a complex issue, and the impacts of such features on traffic crashes is critical to the development of appropriate access management strategies. The purpose of this study was to provide a quantitative evaluation of how crash risk on multi-lane and two-lane highways varies with respect to access spacing in support of the development of a revised access management policy. Data were obtained for approximately 1,247 miles and 5,795 miles of segments across multilane and two-lane highways, respectively. Crash data were obtained for a five-year period from 2012 to 2016 and a series of random effect negative binomial regression models were estimated for each facility to examine the association between crash frequency, access point spacing, and traffic volume. For both facility types, crashes were found to increase consistently as the average spacing of access points along road segments decreased. Crash rates were highest when consecutive accesses were within 150 ft of one another and the frequency of crashes decreased substantively as spacing was increased to 300 ft and, particularly, 600 ft. With spacing beyond 600 ft., crash rates continued to decrease, though these improvements were less pronounced than at the lower range of values. These findings were generally consistent on multilane and two-lane highways.

Study Citation: Hamzeie, R., M-U. Megat-Johari, I. Thompson, T. Barrette, T. Kirsch, and P. Savolainen. "Examining Safety on Two-Lane and Multilane Highways in Consideration of Access Spacing". Presented at the 98th Annual Meeting of the Transportation Research Board, Paper No. 19-05377, Washington, D.C., (2019).

CMFs Associated With This Study

Category: Access management

Countermeasure: Increase density of access points

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.368-36.83 StarsOtherAllNot specifiedNot specified
3.473-247.33 StarsOtherAllNot specifiedNot specified
1.172-17.23 StarsOtherAllNot specifiedNot specified
3.92-2923 StarsOtherAllNot specifiedNot specified