This paper describes an exploratory study that re-examined the use of clear zones as the preferred rural roadside treatment to address fixed object crashes, as compared to barrier treatments, within the context of a Safe System’s approach to road safety. Traditionally, a clear zone of up to nine metres is recommended on a straight section of road. A sample of crashes from the Centre for Automotive Safety Research (CASR) in-depth crash investigations in South Australia was analysed to determine the typical dynamics of vehicles in single vehicle run of road crashes, with a particular focus on the lateral departure distance and the departure angle of the vehicle. A number of these crashes were simulated using advanced computer techniques to determine the relative merits of clear zones and barrier protection. The relationship between the speed of the vehicle and its lateral distance from the edge of the road throughout the departure event was investigated. The merit of barrier protection was assessed by determining the barrier normal velocity at differing barrier protection offsets. Initial analyses showed that in crashes where no fixed object was struck, all vehicles travelled well beyond the nine metre clear zone, with several travelling over 20 metres laterally. Simulations suggest that adequate clear zones to ensure noninjurious impact speeds can not be provided in most situations. Roadside barrier protection in combination with narrower clear zones may provide the most cost effective way to treat rural roadsides to achieve a Safe System.
[1]
Jerry L Graham,et al.
EFFECTIVENESS OF CLEAR RECOVERY ZONES
,
1982
.
[2]
Eric Hildebrand,et al.
Relating roadside collisions to highway clear zone width
,
2007
.
[3]
Malcolm H. Ray,et al.
Characteristics of Fixed‐Roadside‐Object Side‐Impact Accidents
,
1991
.
[4]
Thomas W Kennedy,et al.
MEDIANS OF DIVIDED HIGHWAYS--FREQUENCY AND NATURE OF VEHICLE ENCROACHMENTS
,
1966
.
[5]
Judson B. Welcher,et al.
SYSTEM-BASED ENERGY AND MOMENTUM ANALYSIS OF COLLISIONS
,
1998
.
[6]
R Elvik,et al.
The safety value of guardrails and crash cushions: a meta-analysis of evidence from evaluation studies.
,
1995,
Accident; analysis and prevention.
[7]
P J Cooper.
Analysis of roadside encroachment data from five provinces and its application to an off road vehicle trajectory model
,
1981
.
[8]
N Candappa,et al.
Flexible barrier systems along high-speed roads: a lifesaving opportunity
,
2003
.
[9]
Ernst Tomasch,et al.
Single Vehicle Accidents, Incidence and Avoidance
,
2008
.
[10]
Charles N. Kurucz,et al.
AN ANALYSIS OF THE INJURY REDUCTION CAPABILITIES OF BREAKAWAY LIGHT STANDARDS AND VARIOUS GUARDRAILS
,
1984
.
[11]
N. Haworth,et al.
VISION ZERO: AN ETHICAL APPROACH TO SAFETY AND MOBILITY
,
1999
.
[12]
Terry D. Day.
Validation of the SIMON Model for Vehicle Handling and Collision Simulation - Comparison of Results with Experiments and Other Models
,
2004
.