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 |  | 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 | | 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 | | 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 | | 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 | | 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 | | 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 | | Run off road | K,A,B,C | Not Specified | Rural |
