Study Details

Study Title: Effect of Clear Zone Widths on Run-off-road Crash Outcomes

Authors: Jurewicz and Pyta

Publication Date: 2010

Abstract: Current guidelines on clear zone selection and roadside hazard management adopt the US approach based on the likelihood of roadside encroachment by drivers. This approach is based on the available research conducted in the 1960s and 70s. Over time, questions have been raised regarding the robustness and applicability of this research in Australasia in 2010 and in the Safe System context. This paper presents a review of the fundamental research relating to selection of clear zones. Results of extensive rural highway statistical data modelling suggest that a significant proportion of run-off-road to the left casualty crashes occurs in clear zones exceeding 13 m. They also show that the risk of runoff-road to the left casualty crashes was 21% lower where clear zones exceeded 8 m when compared with clear zones in the 4 - 8 m range. The paper discusses a possible approach to selection of clear zones based on managing crash outcomes, rather than on the likelihood of roadside encroachment which is the basis for the current practice. It is expected that this approach would encourage selection of clear zones wider than 8 m when the combination of other road features suggests higher than average casualty crash risk.

Study Citation: Jurewicz, C. and Pyta V. "Effect of Clear Zone Widths on Run-off-road Crash Outcomes." 2010 Australasian Road Safety Research, Policing and Education Conference, Canberra, Australia, (2010).


CMFs Associated With This Study

Category: Alignment

Countermeasure: Change grade from positive or zero to negative

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.3 -30 3 Stars Run off road K,A,B,C Not Specified Rural

Countermeasure: Change the horizontal curve radius from greater than 1500m to between 600m and 1500m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.42 -42 3 Stars Run off road K,A,B,C Not Specified Rural

Countermeasure: Change the horizontal curve radius from greater than 1500m to less than or equal to 600m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
2.44 -144 3 Stars Run off road K,A,B,C Not Specified Rural

Category:Roadside

Countermeasure: Change clear zone from greater than or equal to 8m to between 2m and 4m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.6 -60 3 Stars Run off road K,A,B,C Not Specified Rural

Countermeasure: Change clear zone from greater than or equal to 8m to between 4m and 8m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.27 -27 3 Stars Run off road K,A,B,C Not Specified Rural

Countermeasure: Change clear zone from greater than or equal to 8m to less than or equal to 2m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
2.19 -119 3 Stars Run off road K,A,B,C Not Specified Rural

Category:Roadway

Countermeasure: Change travel lane plus sealed shoulder width from greater than or equal to 3.5m to less than 3.5m

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
1.21 -21 3 Stars Run off road K,A,B,C Not Specified Rural