Effects of Phi and View Angle Geometric Principles on Safety of Multi-Lane Roundabouts

Abstract

Conventional intersections that have been replaced by multi-lane roundabouts have experienced a substantial reduction in both injuries and fatal crashes. Property-damage-only (PDO) crashes have also been reduced at some of these roundabouts. However, some multi-lane roundabouts have experienced a significant increase in PDO crashes. The question arises as to why some U.S. multi-lane roundabouts have substantially higher numbers of PDO crashes while other outwardly similar roundabouts do not. In this paper, we examine the hypothesis that the cause of the higher numbers of PDO crashes at some U.S. multi-lane roundabouts is driver confusion, owing to the lack of adherence to horizontal geometric safety design principles related to entry angles. We review research and explore three case studies where adherence to the safety principles related to entry angles—Phi and left view angle—contributed to improved safety.

Keywords

infrastructure roadway design roundabouts and other intersection design and control strategies multi-lane roundabouts roundabout safety and operations

Get full access to this article

View all access options for this article.

References

Kansas State University Roundabout Listserv. Discussion on Problem Roundabouts. Kansas State University, Manhattan, listserv.ksu.edu, January 2018.

Chiu

Zhixia

Bill

Noyce

Roundabout Performance Functions of Wisconsin and Comparison with National Models. 94th Annual TRB Meeting Compendium, Transportation Research Board, Washington, D.C., 2015.

Qin

Bill

Chitturi

Noyce

, Evaluation of Roundabout Safety. Paper No. 13-2060. 92nd Annual TRB Meeting Compendium, Transportation Research Board, Washington, D.C., 2013.

Roundabout User Questionnaire. Washtenaw County Road Commission. Ann Arbor, MI, 2016.

National Cooperative Highway Research Program. NCHRP Report 600: Human Factors Guidelines for Road Systems. 2nd ed. Transportation Research Board of the National Academies, Washington, D.C., 2012.

Brown

The Design of Roundabouts. Transport and Road Research Laboratory, HMSO, London, England, 1995.

National Cooperative Highway Research Program. NCHRP Report 672: Roundabouts: An Informational Guide. 2nd ed. Transportation Research Board of the National Academies, Washington, D.C., 2010.

Maycock

Hall

R. D.

Accidents at 4-arm Roundabouts. TRRL Report No. LR 1120. Transport and Road Research Laboratory, Department of Transport, Crowthorne, England, 1984.

National Cooperative Highway Research Program. NCHRP Report 572: Roundabouts in the United States. Transportation Research Board of the National Academies, Washington, D.C., 2007.

10.

Highway Safety Manual (HSM), American Association of State Highway Transportation Officials (AASHTO), Washington, D.C., 2010.

11.

Pulvirenti

Distefano

Leonardi

Tollazzi

Are Double-Lane Roundabouts Safe Enough? A CHAID Analysis of Unsafe Driving Behaviors. MDPI-Safety Journal, Vol. 7, No. 1, 2021, p. 20.

12.

Riccardi

M. R.

Augeri

M. G.

Galante

Mauriello

Nicolosi

Montella

Safety Index for Evaluation of Urban Roundabouts. Accident Analysis & Prevention, Vol. 178, 2022, p. 106858. https://doi.org/10.1016/j.aap.2022.106858.

13.

Montella

Identifying Crash Contributory Factors at Urban Roundabouts and Using Association Rules to Explore Their Relationships to Different Crash Types. Accident Analysis and Prevention, Vol. 43, No. 4, 2011, 1451–1463.

14.

Johnson

Safety Impacts of Signing and Pavement Markings on Property-Damage-Only Crashes at Multi-lane Roundabouts. Transportation Research Record: Journal of the Transportation Research Board, 2019. 2673: 477–488.