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3.1Gaps in research

It is evident that factors contributing to heavy vehicle crashes resulting in serious injury or death to any occupants involved have been well documented. However, technologies continue to evolve leading to advancements in vehicle and road design. As such the continued evaluation of factors that contribute to HV crashes is warranted to ensure that strategies to reduce heavy vehicle crashes address the relevant issues.

Evidence also indicates that when other vehicles are involved in HV crashes, the HV driver is often not deemed at fault. Where HV drivers are at fault, including single vehicle crashes, driver issues such as alcohol and substance use, fatigue, and inattention are common factors. One possible interpretation of these statistics is that there is potentially a sub-set of heavy vehicle drivers that are inherently more dangerous on the roads than the wider HV driver population. An interesting line of research derived from this interpretation would seek to investigate this further. Such research should potentially seek to develop a profile of high risk heavy vehicle drivers that might consider a number of driver and vehicle characteristics; characteristics of the operations for which high-risk HV drivers work may also be worthy of further investigation. Benefits of this research could include:

Provide intelligence to inform enforcement and compliance practices.
Identify drivers and operations that may require particular attention with regard to HV safety.
Identify targets for intervention within the high risk HV driver’s environment. These may include management aspects of the transport operation in which they are employed, characteristics of the vehicle (such as age, maintenance record, safety features, and type of vehicle), and the characteristics of the work environment (e.g., working hours, trip length, etc.).

Other aspects of heavy vehicle safety that appear to be overlooked are heavy vehicle crashes of lower severity and near misses. The availability of data relevant to such crashes is not available from traditional sources and some other approach to investigation would be required. Understanding factors that influence heavy vehicle crashes with minor severity outcomes may have some inherent value for improving safety and productivity for trucking companies.

4Road and vehicle design, and infrastructure planning

This section addresses research regarding the safety implications of the design of roads and vehicles. It addresses areas such as road infrastructure (engineering treatments, line markings, and roadside hazard), road features (e.g., intersections, road alignment, road condition), traffic management (signage, route access), vehicle features (underrun protection, safety technologies, mass efficiency), and heavy vehicle interactions with other road users.

As identified in section three, the design of roads and road infrastructure can have important implications for the involvement of heavy vehicle in crashes. Furthermore certain design aspects of heavy vehicles are related to a heavy vehicle’s risk of crashing and the outcomes of that crash for both the heavy vehicle occupants and other people involved in the crash as occupants of a passenger vehicle, motorcyclist, cyclist, or pedestrian.

Table 4 .6 outlines research relevant to the design of roads and infrastructure that have important safety implications for heavy vehicles. Some of the key findings from this research include:

Road design and infrastructure could be improved to better accommodate heavy vehicles, particularly along freight routes.
Road design should consider factors such as horizontal alignment and the impact of heavy vehicles on the road surface.
Simple measures such as sealing shoulders along freight routes are a cost-effective means of improving safety.
The use of truck climbing lanes and lane restrictions for heavy vehicles provide some safety benefits without major disruptions to overall traffic flow.
Rest areas throughout Australia are inadequate and do not meet established standards with regard to location and the facilities that they provide.
Freight networks in urban areas could be improved to better accommodate heavy vehicles.

Table 4 .7 provides an overview of research relevant to the safety implications associated with the design of heavy vehicles. Key findings of this research include:

The crashworthiness of truck cabins is generally poor due to the lack of protection afforded during roll over crashes. Cabins also fail to prevent objects intruding into the cabin space.
The loading of heavy vehicles directly influences the dynamic stability of the vehicle.
The enforcement of design standards could be improved, particularly with regard to underrun protection.
Australian and international research indicates that there are a range of braking options that improve the braking performance and safety of heavy vehicles.
There are a number of design options for increasing the roll stability of heavy vehicles.
Design features such as underrun protection that exploit the crashworthiness of passenger vehicles reduce the severity of some crash types for other road users, including cyclists.
Improving the visibility of heavy vehicles, particularly side-on visibility, under poor lighting conditions improves safety for other road users.

Table 4 .8 summarises research relating to the benefits, use, or development of technologies that have the potential to improve the safety of heavy vehicles. Findings indicate:

A number of technologies are available that have demonstrated benefits with regard to reducing the risk of a range of crash types including:
- intelligent speed adaptation (ISA)
- weigh-in-motion (WIM)
- electronic stability control (ESC)
- roll stability control (RSC)
- antilock braking systems (ABS)
- warning devices for rollover, collision, and lane departure.
Intelligent transport systems (ITS) are improving safety for all road users by controlling, amongst other things, route access, speed limits, and traffic signal timing.
An emerging ITS technology with large potential for all road users involve Digital Short Range Communications (DSRC) which allow vehicles to communicate with each other or the road infrastructure.
Manufacturers are increasingly fitting enhanced safety features to heavy vehicles; the penetration rate of these features in the heavy vehicle fleet is more rapid than that of the general vehicle fleet.
Technology can be used to improve safety and compliance. There is potential for the collected data to be used for traffic management.
Driver acceptance of new technology and aids is an important issue for consideration.

Table 4 .9 outlines research relevant to safety issues arising through the interaction between heavy vehicles and other vehicles. One of the major safety issues associated with heavy vehicle and other vehicle interaction are the differences in size and mass. Heavy vehicles with higher mass pose a higher risk of injury to most other road users. Naturalistic observations of heavy vehicle-light vehicle interactions suggest that the majority of safety-related (i.e., crashes and near misses) interactions appear to be initiated by the drivers of light vehicles.

Table 4.6

Road and infrastructure design implications for heavy vehicle safety

Authors	Type	Availability	Research	Findings
Chen, Chen, & Wu (2011)	Journal article	Public	Study of historical data for single vehicle truck crashes on a “typical mountain highway” in Colorado.	Adverse road conditions contributing to crashes on mountain highway included icy road surface, windy conditions, and graded curves.
Rumar, Sivak, Traube, & Miyokawa (1999)	UMTRI report	Public	Examination of the visibility of retroreflective pavement markings from trucks and cars.	Higher mounted headlights increased the distance of detection, implying that such pavement markings are more visible to truck drivers than car drivers.
Alvarez (2007)	FMCSA Tech brief	Public	A synthesis of literature regarding heavy vehicle interactions with highways.	Where steep upgrades reduce truck speed by 16km/h, truck climbing lanes should be considered. Long steep downgrades may lead to overheated brakes and a reduced ability to decelerate. The US provides warning signs and brake check areas, warning signs, and emergency escape ramps. Intersection features that need to be considered based upon the presence and frequency of heavy vehicles include kerb return radii for right turns (US), storage lengths for turn lanes, median widths on highways, and offset between opposing left-turn (US) lanes. Most evaluations of safety strategies that restrict trucks to only the right lane (US) show no positive or negative safety effects for such restrictions. The height of heavy vehicles can obscure highway signs to other road users. This has been overcome by including advance warning signs, and placement of signs overhead and on both sides of highways. Yellow light and red light clearance timing at light controlled intersections is an important consideration for trucks.
Smith, Baron, Gay, & Ritter (2005)	FMCSA report	Public	Report identifying the issues relevant to the provision of real-time information on parking availability to truck drivers on the road. Also outlines, to some extent, how truck drivers make use of different parking options.	The 4 areas most often used by truck drivers were public rest areas, privately owned truck stops, other private locations (e.g., loading docks), and the roadside. Truck stops were generally preferred for overnight rests and public rest areas for short naps. Desired attributes of long-term rest locations include food, fuel, restrooms, phones, showers, convenience to the highway, and well-lit parking areas. Surface evaluation of space availability versus demand suggests adequate provision of parking, however it was also noted that a number of regions do not have spacing sufficient to meet the demand. Lack of parking spaces is an issue for drivers seeking to maximise productivity by driving as far as possible under hours of service rules only to have no legal or suitable parking available to them. These drivers often stop on the side of the road creating potential safety hazards for themselves and other road users.
Geoff Anson consulting and InfraPlan (Aust) (2010)	Austroads report	Public	Examines the potential of using locations in industrial areas for heavy vehicle parking in order to supplement the provision of roadside rest areas.	Such a strategy should be used to supplement rather than provide an alternative to existing roadside facilities. Available options include on-street parking using existing council controlled roads, and off-street parking making use of privately owned spaces, or the development of new areas. Due to a number of administrative and technical reasons there is limited potential to use locations in industrial areas for parking heavy vehicles.
Su & Luk (2006)	Austroads report	Public	An investigation of the existing and future vehicles fleet mix in order to improve the level of service to freight, public transport, and emergency vehicle road users. Utilises data from the ABS Survey of Motor Vehicle Use.	Freight vehicles accounted for 17% of total vehicle kilometres travelled in all capital cities in 2004. Freight vehicles need to be properly managed in urban traffic systems due to the size and growth of the freight task. Available measures to improve level of service for road freight operations include changing land use regulations, multi-modal supply chain management, and various freight ITS measures.
Ramsay & Prem (2000)	Austroads report	Public	A report outlining the assessment of route suitability for heavy vehicles	The lane width requirements for trucks is based on vehicle configuration, length, and the road crossfall profile. Each state and territory has produced a network of routes that are suitable for four different classes of vehicle: general access, B-double, and road train types 1 & 2. Issues that should be considered in route assessments include: dimensional capacity, road safety, railway issues, community concerns, environmental issues, geometry, structural capacity, traffic conditions, operational issues, and future development.
Han, Green, Cairney, & Luk (2010)	Austroads report	Public	A report on measures for managing the safety of heavy vehicles at passive and active railway level crossings. Heavy vehicle crashes at level crossings are reviewed. Measures to mitigate the risk of crashes are also reviewed.	From 2003-2007 79 crashes at level crossings in Australia and New Zealand involved heavy vehicles, the majority of which involved articulated trucks. A number of actions were recommended, including: review of Standards Australia AS1742.7 and S10 of the Guide to road design part 4: intersections and crossings, with a particular focus on sight distance requirements. Development and promotion of a uniform restricted access vehicles permit. Promote the use of IAP to measure and monitor driver behaviours at level crossings. Amend where appropriate traffic management and road design guidelines and standards.
Geoff Anson consulting and InfraPlan (Aust) (2009)	Austroads report	Public	A report providing guidelines for use by key stakeholders to assess applications by heavy vehicle operators for access to local roads.	Outlines principles that should govern access to local roads, identifies the need for strategic thinking, the role of road network plans, and the importance of joint planning for transport and land use that involves important key stakeholders.
Geoff Anson consulting and InfraPlan (Aust) (2007)	Austroads report	Public	Outlines processes for identifying and planning rural and urban freight routes of importance.	A number of approaches have been utilised to identify freight routes for different purposes and contexts. Examples of approaches for high wide and commodity based networks that could be adopted across Australia are provided.
Houghton, McRobert, Patrick, & Tsolakis (2003)	Austroads report	Public	A report to serve as a guide to deal with planning issues associated with development projects that will affect freight movements in urban areas.	Planning for freight in urban areas will involve transport management professionals and urban planners. In the past urban freight has had little influence over transport and land use planning, however increases in the freight task and urban freight are driving a need for change in these areas.
Trevorrow & Wright (2011)	Report	Public	A literature review of existing studies and equipment relevant to the measurement of loads and stresses applied to pavement by heavy vehicles and resulting wear on the pavement surface.	Damage to pavements mainly occurs during braking, acceleration, and turning manoeuvres. Turning causes the most damage. In order to understand the impact of next generation freight vehicles on pavement surfaces it is necessary to quantify the horizontal tyre forces and pavement surface wear mechanisms. This needs to involve the application of full-scale loads under realistic tyre to pavement contact and temperatures, ruling out lab-based techniques.
Cunningham (2002)	Report	Public	A report outlining the truck-based geometric design standards for roads. Also includes traffic volumes and mix at which the adoption of such standards is economically viable.	Truck design performance characteristics were derived from the literature with a particular focus on the characteristics of the 6-axle semi trailer (typically the most common truck type on inter-regional freight routes). Based on the parameters identified a number of design standards were developed, including: horizontal curve standards based on limiting lateral acceleration, crest vertical curves based on stopping sight distance, horizontal curve radii and lateral clearances based on stopping sight distance, acceleration lane lengths, and vertical grades.
Gates & Noyce (2010)	Journal article	Public	An investigation of dilemma zone behaviour including brake response time, deceleration rate, and red light running at signalised intersections in Wisconsin. Data was obtained from 1,275 vehicles (motorcycles, cars, light trucks, single-unit truck, and tractor trailers).	Deceleration rates were highest for cars and light trucks (SUVs, etc.). Single unit trucks and tractor trailers demonstrated lowest deceleration rates. Deceleration rates were higher during off-peak times. Tractor trailers and single-unit trucks were 3.6 and 2.5 times respectively more likely to run a red light compared to passenger vehicles. Red light running was 1.3 times more likely during peak times compared with off-peak periods.
Chatti, Manik, Salama, Brake, Haider, El Mohtar, & Lee (2009)	Report	Public	An investigation of the impact of multi-axle trucks on pavement damage. 5 axle configurations and 5 truck configurations were studied.	Rutting damage due to different axle configurations is proportional to the number of axles; the damage per load carried is constant for individual axles. Fatigue damage due to different axle configurations increases with an increasing number of axles within an axle group for a given stress ratio.
Chatti, Manik, Salama, Brake, Haider, El Mohtar, & Lee (2009)	Report	Public	A study of the impact of multi-axle trucks on flexible and rigid pavement systems with a focus on flexible systems.	Multiple axle groups were found to have less damage in fatigue per load carried for both pavement types, however they were found to cause more damage in rutting of flexible pavements and roughness for rigid pavements. Testing of asphalt concrete indicated that multiple axles case less fatigue damage per load carried and rutting is proportional to the number of axles within the axle group. Mechanistic analysis demonstrated that multiple axles cause considerable stress reduction leading to lower fatigue damage. Full scale slab testing to examine joint/crack deterioration in plain concrete pavements was inconclusive.
Chatti, Manik, Salama, Brake, Haider, El Mohtar, & Lee (2009)	Report	Public	A study of the impact of multi-axle trucks on flexible and rigid pavement systems with a focus on rigid systems.	Multiple axle groups were found to have less damage in fatigue per load carried for both pavement types, however they were found to cause more damage in rutting of flexible pavements and roughness for rigid pavements. Mechanistic analysis demonstrated that multiple axles cause considerable stress reduction leading to lower fatigue damage. Multiple axles cause more faulting in rigid pavements.
Davis (2004)	Conference paper	Public	Addresses new developments and considerations for the design of downhill road sections with respect to the braking of heavy vehicles.	Considers issues associated with sustainable braking at various slopes and speeds. Engine braking and difference in various engine retarders are explored with regard to how these devices assist in the survivability of descents by heavy vehicles.
Di Cristoforo, Sweatman, & Kidd (2004)	Conference paper	Public	A presentation of findings from field trials evaluating the acceleration and deceleration performance of different heavy combination vehicles ranging in mass from 44 to 166 tonnes.	Tests carried out during the trials included acceleration from rest and deceleration from initial speed. These provide measures on the time to travel distance, time to reach speed, distance to reach speed, stopping distance, and average acceleration/deceleration for different heavy vehicles.
Prem, Ramsay, Fletcher, George, & Gleeson (1999)	Austroads report	Public	Reports on the findings of a performance-based method of assessing heavy vehicles for route access using computer modelling of the tracking ability of heavy vehicles.	Tracking ability is dependent on the cross-slope profile of the road, vehicle configuration, and travelling speed. Most heavy vehicles could travel comfortably on roads with a useable lane width of 3.5 metres with the exception of rigid-plus-three and A-triple configurations travelling at or above 90km/h.
Jurewicz & Comport (2008)	Austroads report	Public	An audit of rest areas along 12,700km of (mostly) AusLink freight routes. More detailed audits were carried out for 147 rest areas.	None of the audited routes fully met the spacing recommendations of the national guidelines; 60% of audited routes had significant deficiencies in the provision and frequency of rest opportunities. Major rest areas were under-provided in all jurisdictions. Three quarters of rest areas were not duplicated correctly on the opposite side of the road, with the exception of rest areas in Tasmania. Detailed audits revealed a relatively high compliance with recommended minimum parking requirements for different categories of rest areas. On average two thirds of recommended minimum site facilities were provided. Recommendations: the development of an empirical parking supply model for rest areas. Evaluation of the potential impacts of changes to driving hours regulations with regard to the provision of rest stops (rest area guidelines should be amended in line with these findings).
Borchardt (2002)	Journal article	Public	Analysis of safety benefits of truck restrictions of a 6 mile stretch of Houston freeway .	Traffic crashes were reduced by 68% without disruptions to freeway operations, travel time, or traffic patterns.
Bennett, Styles, Yeo, & Cox (2003)	Austroads report	Public	Examines the consequences of the introduction of PBS as a means of maintaining road safety and protecting road infrastructure.	Significant productivity benefits can be expected from the introduction of PBS in the Australian freight industry. Effective compliance strategies would provide benefits, including safety, to all stakeholders.
Lindsey (2009)	Conference paper	Public	A review of the potential benefits from separating cars and trucks into different lanes or roads.	Potential benefits depend on the relative volumes of cars and trucks, capacity indivisibilities and the safety hazard presented by each vehicle type. Differentiated tolls can support efficient allocations of cars and trucks between lanes. Lane access restrictions were observed to have limited effectiveness.
Fontaine, Dougald, & Bhamidpati (2009)	Report	Public	A report of the safety and mobility impacts of Virginia’s truck lane restrictions.	Crash analysis of high-volume three lane segments revealed that crashes were higher than expected after the restriction was put in place and were not the products of growing congestion. Due to a high level of non-compliance with the restrictions no safety benefits were found for the restrictions on 2-lane interstates. Enforcement improved compliance, however this improvement was modest.
Fontaine (2008)	Journal article	Public	Reports the safety and operational findings of an evaluation of lane restrictions on four-lane interstate segments in mountainous areas lacking in truck climbing lanes.	Positive trends in crashes were observed with the number of fatal and injury crashes showing a significant decline. Compliance with restrictions in the evaluated areas was generally good, however a number of slow-moving vehicles (including cars) were still found to impede traffic in the left lane.
Jacques, Franklyn, Corben, & Candappa (2003)	Report	Public	An analysis of heavy vehicle run-off-road crashes in Victoria between 1998 and 2001 to determine the performance of safety barriers.	There is limited information available regarding the performance of barriers in impacts with heavy vehicles.
Milliken & de Pont (2004)	Transfund New Zealand research report	Public	The relationships between cross-sectional geometry and HV performance were used to estimate the effects of road geometry on HV crash risk.	The areas with potential for significant benefits in the reduction of HV crash risk include banking in curves, seal width and shoulder treatments, and cross-slope due to camber.
Mugarula & Mussa	Book	Public	A study to determine the operational and safety impacts of the restriction of trucks from using the median lane of a six-lane freeway corridor in Florida.	The difference between truck and passenger car speeds and travel times were insignificant on the unrestricted middle and shoulder lanes. Trucks were able to use the middle lane to pass 25% of the time during the truck peak-hour period with the assumption of a 10-s gap acceptance. Opening all lanes to trucks increased the number of lane-changing maneuvers by 11% in the daytime, which has the potential to increase the risk of crashing.
Andreassen (2003)	Conference paper	Public	An examination of HV crash data with regard to road design and roadside features.	There are areas of road design that do not cater for larger vehicles. The whole road system could be rebuilt to suit large vehicles. The use of large vehicles should be limited to specific road classes and routes. The design of HVs needs to be reconsidered to afford the driver greater vision of the area around their vehicle. Traffic regulations should be renewed and penalties for offences involving HVs should be greater than those for LVs.
McLean (2002)	Conference paper	Public	Suggests potential improvements to roads that are both cost effective and have the potential to reduce truck crash risk on two lane roads.	Roadside improvements including the retrofitting of shoulder seals was identified as a possible solution. Roads designed for low volume car and rigid truck traffic that are now part of the national truck freight route require particular attention.
Schneider, Zimmerman, Van Boxel, & Vavilikolanu (2009)	Journal article	Public	Uses statistical modeling methods to determine the effects of horizontal alignment on HV crashes.	A significant increase in truck crashes due to horizontal curvature and passenger vehicle volumes was observed.
Ko, Washburn, & McLeod (2009)	Journal article	Public	A study to determine the roadway, traffic, and control issues that should be the focus of efforts to better serve the needs of the trucking community.	On freeways, speed variance and pavement quality were important factors. On two-lane highways, important factors included percentages of time following or being followed, travel lane and shoulder width and pavement quality. On urban roads factors included ease of performing turning manoeuvres, speed variance, traffic density, and pavement quality. The behaviour of other drivers, pavement condition, level of congestion, and frequency and timing of road works were common factors independent of road type.
Reyner, Horne, & Flatley (2010)	Journal article	Public	Analysis of the effectiveness of motorway service areas in the UK at reducing the number of sleep-related crashes. Effectiveness was assessed by comparing crashes in the 16km following a service area to crashes in the 16km leading up to the service area. Crashes involving all vehicle types were included.	There was a non-significant reduction in crashes in the 16km following a rest area. There was a significant reduction in sleep-related crashes in the 16km following a rest area. The greatest reduction in sleep-related crashes that were potentially due to the provision of service areas was found for cars. Service areas seemed to have the least influence on sleep-related crashes between 2-6am, the time period when the greatest number of sleep-related crashes occur.

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