Some implications from the in-depth study and simulation modelling of road departure crashes on bends on rural roads

Previous work by the authors has questioned the philosophy of reliance on clearzones, rather than barriers, for rural road safety. In-depth investigation and simulation modelling of a sample of real world crashes has highlighted that even if clearzones of 10 metres could be achieved throughout the rural road network, there are certain vehicle control mechanisms that are not adequately accommodated when a vehicle departs the road. This paper extends this work based on 64 investigated crashes on rural roads at bends and nine computer simulations of these crashes. Bends are over-represented in rural crashes yet the provision of clearzones tends to mimic that of straight sections of road in practice. The study summarizes the characteristics of the investigated crashes in the context of departures and vehicle control mechanisms and discusses the implications of the findings on the provision of safety features on rural roads. The provision of roadside barriers is also discussed including location relative to the bend and offset from the edge of the traffic lane.Doecke, S., & Woolley, J

Post impact travel and secondary impacts following urban intersection collisions

This paper describes the path of vehicles following a collision with another vehicle at a metropolitan intersection. The aim was to provide guidance to transport authorities on roadside design at intersections to protect vehicles from secondary collisions with roadside objects. Detailed information from in-depth investigations of 78 intersection crashes were analysed. Crashes at signalised and unsignalised intersections were analysed separately. Secondary collisions with roadside objects were identified with 16 signalised and 16 unsignalised intersection cases. Nine of these 32 collisions were more severe than the initial vehicle-to-vehicle collision, three at signalised intersections and six at unsignalised intersections. Of the 78 intersection crashes, more than half of the vehicles came to rest within 10 metres of the impact point. More than a quarter travelled 15 metres or further and approximately 10% travelled further than 27 metres. It was found that 28 of the 70 crash involved vehicles at signalised intersections encroached into the designated pedestrian crossing areas. It was also found that 10 of those vehicles departed the roadway. The study has indicated the most likely locations that vehicles will traverse following collisions at urban intersections. This information can be used by road designers to make decisions in relation to the protection or removal of roadside objects in the vicinity of intersections.Doecke, S., & Woolley, J

Advisory Intelligent Speed Adaptation for government fleets

This project sought to determine the likely crash savings if state government fleets in Australia were fitted with advisory Intelligent Speed Adaptation (ISA). The cost effectiveness of such a fitment was assessed considering if the ISA device is kept within the government fleet (scenario 1) or if it is left in the government vehicle when it is sold (scenario 2). Data from the fleet vehicles involved in the recent NSW ISA was used. The reduction in crash risk was calculated by applying Kloeden’s risk curves for travel speed to the “before” speed profile and the “ISA active” speed profile found in the trial. The reduction in risk was then estimated in terms of the difference in the total crash risk produced by these speed profiles. ISA was found to have the potential to reduce casualty crashes in government fleets by 20%. It was estimated that this would eliminate 171 casualty crashes involving state government vehicles per year and save $31.6 million in crash costs per year. Scenario 1 was more cost effective than scenario 2, although the wider benefit to the community produced by scenario 2 was not taken into account. Of the four ISA devices considered the navaid device that included ISA functionality was found to be the most cost effective.SD Doecke, RWG Anderson, JE Woolle

Post impact trajectory of vehicles at rural intersections

This report describes the path of vehicles following a collision with another vehicle at a rural intersection. Detailed information from in-depth investigations of 70 intersection crashes was analysed. Rear end crashes at intersections were excluded as were collisions involving a motorcycle. The vehicle which had right of way most commonly had an impact speed of between 80 and 99 km/h and the impact point was on the front of the vehicle. The vehicle which was required to give way most commonly had an impact speed of between zero and 20 km/h and was struck between the front of the vehicle and the B-pillar. After the vehicle to vehicle impact half the vehicles travelled more than 18 metres, 20% more than 34 metres and 10% more than 50 metres from the centre of the intersection. The most common direction of the vehicle following the initial impact was found to be between 15 and 29.9 degrees, where the original direction of travel of the through vehicle is at zero degrees. Intersection geometry, speed zone, impact point and mass ratio influence the nature of the post impact trajectory of the vehicles involved. As the results show a high number of vehicles travel a large distance at a shallow angle following an intersection collision, extending crash barriers on the through road (the road with right of way) right up to the intersection may have some benefit. Clear zones surrounding the intersection are also advisable and have an added benefit of increasing sight distance. Hazards can be assessed for removal or relocation by applying the results of this study.SD Doecke, JRR Mackenzie, JE Woolle

Cost benefit analysis of Intelligent Speed Adaptation

This report examines the potential costs and benefits of Intelligent Speed Adaptation (ISA) in Australia. Analysis was conducted to determine the benefits of advisory, supportive and limiting ISA. This analysis suggested advisory ISA would reduce injury crashes by 7.7% and save $1,226 million per year. These figures were 15.1$2,240 million for supportive ISA and 26.4% and $3,725 million for limiting ISA. A cost benefit analysis was conducted considering different implementation scenarios including: all vehicles, new vehicles, fleet vehicles, market driven, heavy vehicles, young drivers and navaid devices. The cost benefit analysis was heavily influenced by the unit price of the ISA devices causing the cost benefit ratios (BCRs) to vary from as low as 0.29 to 4.03 over a 20 year timeframe. The “all vehicles” and “new vehicles” scenarios produced the greatest BCRs although it was thought that, taking into account the elevated risk of young drivers, a combination of implementing ISA on young driver’s vehicles and new vehicles may be the most cost effective implementation scenario. Limiting ISA generally produced the highest BCRs therefore this level of ISA should be implemented wherever possible.SD Doecke, JE Woolle

Vehicle frontal protection system geometry and pedestrian impacts: the effect of AS 4876.1-2002 geometric criteria

Australian Standard AS 4876.1-2002 stipulates requirements for motor vehicle frontal protection systems (VFPS), colloquially known as bull bars. Section 2 of the Standard sets design and installation requirements and has a particular focus on the geometry of the VFPS, stipulating that their geometry should generally conform to the frontal shape of the vehicle. The aim of this project was to examine the differences between pedestrian impacts with vehicles fitted with a VFPS with geometry that meets the requirements of Section 2 of AS48761.1-2002 and VFPS that do not meet these requirements. MADYMO was used to simulate pedestrian impacts with vehicles that had VFPS fitted. The simulations showed that conforming VFPS tend to redistribute impact forces to contacts with the bumper section of the VFPS. For an SUV impact, the increase in risk of pelvic injury produced by this change in loading pattern is only marginally offset by a small reduction in the probability of upper leg injury. For a sedan impact, increased risk in upper leg injury may be offset by a reduction in risk to lower leg injury, depending on the material of the VFPS. Conforming VFPS also tended to result in lower head impact speeds with the vehicle, reducing the severity of the impact with the head, resulting in a reduction in risk of serious head injury well over 50% based on the change in the head injury criterion. The extent to which the results of the narrow set of impact conditions studied can be generalised to all collisions is not completely clear, although it seems reasonable to suggest that the effects will apply where the interaction with the bull bar and the pedestrian is at, or below, the pelvic region. It is less likely that the geometry of the bull bar would affect children to the same extent. The results of this brief simulation study support the expectation that the adoption of Section 2 of AS 4876.1-2002 will lead to reductions in injury risk to people struck by VFPS.SD Doecke, RWG Anderso

Crash reduction potential of connected vehicles in South Australia

Connected vehicle technology allows vehicles to send and receive information to and from one another, other road users and infrastructure. Although it is not yet available on any production vehicle, on-road trials are well under way. It is likely that connected vehicle technology will enter the market at a time when autonomous emergency braking (AEB) is becoming more common on new vehicles. The purpose of the present research was to estimate the safety benefits of connected vehicle technology in Australian conditions over and above what could be provided by AEB. Central to the methodology employed to achieve this was the application of a collision avoidance system model to simulations of real world crashes investigated by CASR to determine the change in impact speed. The collision avoidance system model was used for this project to not only model sensor based AEB systems but comparable connected vehicles systems to determine the additional crash reduction potential of connected vehicles above that provided by AEB. A literature review was conducted and found that connected vehicles have many safety related applications that can address the South Australian crash types of right angle, right turn, rear end, hit pedestrian, side swipe and head on, though technical difficulties exist for hit pedestrian and head on crashes. Importantly, crash types that are poorly addressed by AEB, right angle and right turn crashes and certain pedestrian crashes, can be addressed by connected vehicle applications. It was found that connected vehicle technology could reduce injury and fatal crashes by an additional 16 to 21 percentage points and 12 to 17 percentage points respectively above the percentage reduction of sensor based AEB. If hit pedestrian or head on crashes can not be addressed by connected vehicles the additional reduction is 14 to 18 percentage points and 7 to 12 percentage points for injury and fatal crashes respectively. The potential of connected vehicles to reduce crashes in South Australia is therefore considerable and the uptake of such technology should be encouraged in ways that are shown to be cost effective.SD Doecke, RWG Anderso

Annual performance indicators of enforced driver behaviours in South Australia, 2010

This report was produced to quantify performance indicators for selected enforced driver behaviours (drink driving, drug driving, speeding and restraint use) in South Australia for the calendar year 2010. The level of driver screening tests (DST) for alcohol in South Australia in 2010 increased to the highest level since 2006. The proportion of tests conducted using mobile DST for alcohol was similar to the previous year. The detection rate, based on evidentiary testing, decreased slightly in 2010 and was lower than in two of the three other jurisdictions that supplied comparison data. The level of driver screening testing for drugs increased by three per cent in 2010 from the 2009 level. Testing rates per head of population continued to be the highest in Australia. The drug detection rate rose in 2010, though the level of drug driving among fatally injured drivers decreased slightly, relative to 2009. THC (the active component of cannabis) was the most commonly detected drug. The number of hours spent on speed enforcement in 2010 decreased by three per cent from 2009. The number of speeding detections also decreased relative to 2009 for all types of detection devices. Detections per thousand vehicles passing a speed camera decreased markedly after January in 2010. Systematic speed surveys found reductions in mean travelling speeds on most metropolitan roads but no significant change on rural roads. Speeding by more than five km/h also decreased on most metropolitan roads and also on 110 km/h rural roads. Restraint offences decreased by 10 per cent in 2009. Restraint use in serious and fatal crashes remained lower in rural regions than in the metropolitan area. Males were more likely to be charged with a restraint offence and less likely to be wearing a restraint in a fatal or serious injury crash.SD Doecke, JAL Grig

Cost benefit analysis of Intelligent Speed Adaptation

This report examines the potential costs and benefits of Intelligent Speed Adaptation (ISA) in Australia. Analysis was conducted to determine the benefits of advisory, supportive and limiting ISA. This analysis suggested advisory ISA would reduce injury crashes by 7.7% and save $1,226 million per year. These figures were 15.1$2,240 million for supportive ISA and 26.4% and $3,725 million for limiting ISA. A cost benefit analysis was conducted considering different implementation scenarios including: all vehicles, new vehicles, fleet vehicles, market driven, heavy vehicles, young drivers and navaid devices. The cost benefit analysis was heavily influenced by the unit price of the ISA devices causing the cost benefit ratios (BCRs) to vary from as low as 0.29 to 4.03 over a 20 year timeframe. The “all vehicles” and “new vehicles” scenarios produced the greatest BCRs although it was thought that, taking into account the elevated risk of young drivers, a combination of implementing ISA on young driver’s vehicles and new vehicles may be the most cost effective implementation scenario. Limiting ISA generally produced the highest BCRs therefore this level of ISA should be implemented wherever possible.SD Doecke, JE Woolleyhttp://www.roadsafetyconference2010.com.au/index.htm

Adequacy of barrier and median separation on rural roads

This study reanalyses the data from research by Doecke and Woolley (2010) that examined road departures with regard to clear zones and roadside barriers, in the new context of wide medians and median barriers (i.e. departures to the right side of the direction of travel). This study includes data from 62 rural crash investigations conducted from 1998 to 2010 in rural areas to which an ambulance was called. Many of the vehicles in the sample of in-depth crash investigations collided with fixed objects within 15 metres of the roadway yet still about 13% traversed 15 metres of lateral width from the roadway and had an occupant who needed to be transported to hospital. Of those 10 cases where no fixed object was struck, only five came to rest within 15 metres of the roadway. Computer simulations were performed based on five of the cases, three ‘drift off’ type run off road to the right crashes and two single yaw run off road to the right crashes. Each case was simulated using two different driver scenarios. The simulations revealed that wide medians may cater well for vehicles which drift off the road but those that lose control before departing the road will be likely to cross the median. Furthermore, the vehicles that lost control were found to still be travelling at between 55 and 70 km/h after crossing a 15 metre wide median. The computer simulations were also used to examine the appropriateness of median barrier offsets. The barrier was placed at a range of different lateral offsets from the road to examine the optimal positioning of roadside barriers on both wide and narrow medians. In general, smaller barrier offsets produced less severe impacts but all barrier offsets tested would be acceptable. It was concluded that a 15 metre median would cater for drift off crashes but not loss of control crashes. Therefore, to create a true safe system median barriers must be considered. It is also desirable to have a median that is not as wide as currently recommended when a median barrier is installed. Barriers on narrow medians will safely prevent departures to the right. The exact barrier offset (and therefore median width) on a narrow median had little effect on safety.SD Doecke, JE Woolle