Intelligent Transport Systems: Safety and Human Factors Issues
Royal Automobile Club of Victoria (RACV) Ltd – Report 01/01
Authors: M. Regan, J. Oxley, S. Godley & C. Tingvall
Abstract:
The deployment of Intelligent Transport Systems (ITS) technologies has the potential to yield a new wave of road safety and other benefits for Australia. It is critical for their success, however, that these systems are tailored to the specific safety needs of road users and that human factors knowledge and principles are incorporated into the design, deployment and evaluation of these systems. This report reviews the available literature on human factors and safety issues associated with various classes of ITS technologies, including both in-vehicle systems and out-vehicle systems. Particular emphasis is given to human factors issues associated with in-vehicle ITS technologies and to the potential safety benefits of ITS applications for high risk and vulnerable road users (in particular, young novice drivers, older drivers, pedestrians, motorcyclists, bicyclists and cultural minorities). ITS technologies currently available and under development are reviewed. This report concludes with recommendations for future action and research to better understand and exploit the potential safety benefits of ITS for all road users.
Executive Summary
Purpose of this Report
The purpose of this review, which was commissioned by the Royal Automobile Club of Victoria, is to assess the safety and human factors implications of intelligent transport systems for Victorian road users. The implications of both in-vehicle and out of vehicle IT systems are reviewed, although the emphasis in this report is on in-vehicle systems as these are predicted to yield the greatest potential safety benefits and motorists will have some choice as to whether to purchase these systems.
General Overview
The first section of this report focuses on general human factors and safety issues relevant to ITS technologies. It is noted that, until recently, road safety has been as an incidental by-product of ITS development rather than the central issue guiding the design of systems. This is a consequence of the fact that, to date, the development of ITS applications has been driven by the desire for technological innovation. It is also noted that, at this point in time, it is difficult or even impossible to come to a definitive conclusion about whether a given ITS application will, or will not, enhance safety. The reason for this is that crash studies, which are the traditional measure of a change in road safety, are not (yet) appropriate for deriving safety information in the ITS context because ITS technologies have never been deployed on a large enough scale over a long enough period of time in traffic for the crash numbers to be a reliable indicator of a change in safety.
Human factors issues relevant to ITS applications are considered under three general headings: system reliability (here the main issues centre on human responses to system failure and false alarms); the human machine interface (here key issues centre around how the HMI can be designed to minimise distraction and cognitive workload); and behavioural adaptation (here the main issues centre on how people adapt behaviourally over time to exposure to the systems and how acceptable they find the systems).
The main part of this review focuses on what is currently known about the safety and human factors implications of specific ITS applications for road users generally, both in-vehicle and out of vehicle systems. It is noted that there are three mechanisms by which ITS technologies have the potential to affect road safety: by reducing the possibility of a crash; by reducing the injury consequences of crashes; and by influencing or controlling driver exposure to the road traffic system (i.e., exposure measures). Within these three areas, the potential safety benefits and, in some cases disbenefits, of ITS applications of various kinds are examined.
The final section of the report focuses on what is currently known about the safety and human factors implications of ITS applications for high-risk and vulnerable road users. These include young novice drivers, older drivers, pedestrians, motorcyclists, bicyclists and cultural minorities.
On the basis of the literature reviewed, a number of conclusions can be drawn. These are outlined in the following sections.
ITS Technologies Which Reduce Crash Risk
Several ITS applications reviewed in this report appear to have significant potential to reduce crash risk. The potential safety benefits for some of these systems have been determined from analytical desk top studies, whilst for other systems effectiveness data has been derived from surrogate safety measures obtained from simulator studies and short duration field trials.
Whilst these studies have been undertaken in Europe and in North America, the data deriving from them give some indication of the likely effects of the various systems. For some systems no effectiveness data could be obtained. For these systems, the authors have made a judgement about the likely effectiveness of the systems based on the limited information available.
The following systems would appear to have significant potential to reduce injuries and fatalities by at least 10 percent, with variable speed limiting systems having the highest safety potential of all systems.
- in-vehicle variable speed alerting and limiting systems
- in-vehicle driver impairment monitoring systems such as the European Union-developed SAVE system (which includes driver vigilance monitoring)
- in-vehicle forward collision warning (incorporating headway feedback)
- in-vehicle collision avoidance systems generally (when they become commercially available)
- incident management systems
- automated speed enforcement (e.g., speed and red light cameras)
- roadside speed control systems with variable speed limits
- urban traffic control
- motorway control systems (i.e., variable speed limits, roadside incident detection, weather warnings )
Other systems reviewed which would appear to have considerable potential to reduce crash risk, but to a smaller extent than those identified above, include: lane departure warning systems, lane change collision warning systems, vision enhancement systems and crash data recorders. With the exception of the latter system, these systems require further refinement and trialing before a more precise estimate of their potential to reduce crashes can be made.
On the basis of the literature reviewed, adaptive cruise control and rear collision warning systems are the applications which appear to have the least potential to reduce injury crashes across the whole road transport system. However, it is also noted that emerging rear collision warning systems will have the capacity to reliably detect pedestrians and reduce property damage.
The various human factors issues associated with these systems are discussed.
ITS Technologies which Reduce the Consequences of Crashes
Several ITS applications reviewed in this report appear to have significant potential to reduce the injury consequences of road crashes.
Variable speed alerting and limiting systems have been shown to lead to reductions in vehicle speed and will, as a consequence, have a significant general effect in reducing the injury consequences of crashes. Seat-belt reminder (which are at the advanced prototype stage) and interlock systems (which are relatively simple technically to develop), mayday systems and intelligent restraint systems also offer significant potential safety benefits.
At this point in time ITS technologies capable of distinguishing between different types of vulnerable road users and of rapidly deploying tailored countermeasures (such as active braking or airbags) to reduce injuries in the event of a crash are in their infancy but offer considerable safety potential.
The various human factors issues associated with these systems are discussed.
ITS Technologies Which Affect Exposure to Crash Risk
Exposure is an important moderating variable in road safety. In this report a range of ITS applications is reviewed which affect exposure patterns, and hence safety, either by directly preventing exposure to risk or by affecting the amount or distribution of traffic in terms of routes or transport modes. For most of the applications discussed, very little if anything is known about their potential effects on safety.
Of those applications reviewed, the electronic driver's licence stands out as the application with the most potential to reduce crash risk by preventing unauthorised access to vehicles and by providing a tool for automating the enforcement of driving restrictions placed on a person's licence. The electronic licence can also be used to record driving performance data that can be used to provide feedback to drivers during the critical learning phase. Breath alcohol ignition interlock systems appear to have significant potential to enhance the safety of recidivist drink drivers, at least while they are using the devices. Breath alcohol detection and advisory systems also appear promising from a safety viewpoint, although there is currently no data available known to the authors regarding their likely safety benefit.
The potential safety benefits of in-vehicle navigation assistance systems are yet to be established as the research findings relating to this class of system are varied and contradictory. The on-road research studies reviewed here suggest that these systems have the potential to release mental capacity that can be used to better detect and respond to traffic hazards. In theory, these systems should also reduce exposure as the amount of unnecessary driving is reduced. On the other hand, it has been suggested that these systems have the potential to create new trips, and thus increase exposure, because drivers may feel more comfortable going to unknown destinations.
The various human factors issues associated with these systems are discussed.
ITS Technologies and High-Risk and Vulnerable Road Users
In the final section of this report the safety and human factors implications of the various ITS applications reviewed are considered specifically in relation to certain high-risk and vulnerable road user groups. Very few ITS applications have been developed specifically for high-risk and vulnerable road users. Judgements were therefore made by the authors about the suitability of the technologies reviewed based on the safety and human factors needs of these particular road user groups and based on the findings of previous research involving these groups. The following conclusions can be drawn from this section of the review.
Young novice drivers.Variable speed alerting and limiting systems and electronic driver's licences appear to offer the greatest potential safety benefit for novice drivers. Advanced prototype systems have been developed in Europe and in Melbourne, Australia. Other systems which are either commercially available or are in the advanced prototype stage of development which are also likely to benefit this group are forward collision warning systems (specifically those with headway feedback systems), seat-belt reminder systems, breath alcohol detection and advisory systems, mayday systems and intelligent restraint systems. It is suggested that, if properly designed, ITS technologies can serve as intelligent 'co-drivers' to assist novice drivers in calibrating their driving behaviours to the demands of the traffic management system. Recent developments in ITS communications between vehicles and the road infrastructure in Japan also hold promise for enhancing the safety for novice drivers in the future by minimising the incidence and severity of specific crash scenarios in which they are over-involved (e.g., right through crashes).
Older drivers. A number of ITS applications have considerable potential in enhancing the safety of older drivers. Those having the greatest potential safety benefit are mayday systems, vision enhancement systems, rear collision warning systems and in-vehicle navigation and assistance systems, provided the latter system does not increase exposure to risk by creating new trips for older drivers. Technologies such as lane departure warning and lane change collision warning systems are also likely to enhance the safety of older drivers when they become more reliable. ITS technologies that help older drivers to negotiate their way through intersections are not currently available, but could be expected to yield significant safety benefits. These are currently being developed in Japan.
Pedestrians. The issue of pedestrian safety is one of the few areas in which specifically tailored ITS applications have been developed and recent ITS initiatives in Japan and Europe have focussed on developing systems to detect and protect pedestrians. Speed alerting and limiting devices are likely to confer the greatest benefits in reducing the incidence and severity of crashes involving pedestrians. Mayday systems are likely to indirectly benefit pedestrians in the near future as they reach the market in greater numbers as these systems can be activated in the event of a collision with a pedestrian. Adaptive signal control technologies, such as Puffin crossings, appear to provide relatively minor safety benefits to pedestrians. Re-designing vehicle structures to reduce impact forces on the pedestrian in the event of a crash, and developing systems which detect pedestrians and intelligently deploy countermeasures such as airbags to further minimise impact forces are likely to confer considerable safety benefits. It will be several years, however, before these technologies, and indeed technologies that are capable of both detecting and avoiding pedestrians, become commercially available.
Bicyclists. The ITS applications that are likely to benefit pedestrians are also likely to benefit bicyclists. Variable speed warning and limiting devices, along with mayday systems (in cases where they are equipped to the striking vehicle) are likely to reduce the incidence and severity of crashes involving bicyclists and to enable more rapid emergency assistance. Vision enhancement systems, which are not too far away from being able to reliably detect bicyclists in low visibility conditions, are also likely to enhance the safety of bicyclists. The development of vehicle frontal structures which reduce impact forces on bicyclists in the event of a crash and the development of systems which detect bicyclists, warn the driver of an impending crash, and intelligently deploy airbags to reduce the impact of the crash, are also likely to confer considerable safety benefits. However, it will be several years before these latter systems become available. Automated systems capable of both detecting and avoiding bicyclists are even further away from being commercially available.
Motorcyclists. As for pedestrians and bicyclists, very few ITS applications have been developed specifically for motorcyclists. However, Honda in Japan have equipped 3 demonstration motorcycles with a range of ITS technologies developed to avert crashes through coordination between the road infrastructure and the motorcycle. Those ITS applications considered to have the greatest positive effect on the safety of motorcyclists are variable speed alerting and limiting systems, electronic licences and mayday systems. These are presently available and should be able to be adapted for use by motorcyclists. Other systems that have potential safety benefits for this group are alcohol ignition interlocks, breath alcohol detection and advisory systems and night vision enhancement systems, although these systems will require further research and development before they can be deployed. Systems that make the motorcycle more stable and which minimise the injury to motorcyclists in the event of a collision are also discussed, however these will not be available in the foreseeable future. The uptake by car drivers of lane change warning systems will help them to see motorcyclists in their blind spots but there are currently no collision warnings systems capable of reliably differentiating motorcycles from other vehicles and objects. Enhancements to existing traffic signal systems have the potential to reduce the incidence of right-hand turn motorcycle crashes at intersections.
Cultural minority groups. Child restraint wearing rates in the back seats of passenger vehicles in Victoria, particularly for children of certain adults of non-English backgrounds, are low.
Therefore, seat-belt reminders, or even seat-belt interlocks, may benefit the safety of these occupants.
The Future
General Issues
There is a need for a move away from technology-driven ITS research and development to user-oriented design if ITS technologies are to be successful in reducing the incidence and severity of road crashes. It is important in future that manufacturers be helped with design, development and implementation issues in order to establish a correct balance between safety and other ITS objectives and to prevent uncontrolled development (Rumar et. al., 1999).
In Europe, it is recognised that there is an urgent need for the development of a medium and long-term European Union Strategy that would adequately account for ITS road safety issues. In particular, it is recognised that the European Union needs to develop its role as a provider of advice to industry with regard to the design, development, implementation and evaluation of new ITS products (Rumar et al., 1999). Clearly there is a need for the development of a strategy of this kind in Australia, presumably under the umbrella of the National ITS Strategy, if safety in the development and deployment of ITS technologies is to be taken seriously.
It is unlikely that the demand for in-vehicle ITS technologies will be driven by regulation. Rather, market demand is most likely to drive demand for these systems. In Australia, the major vehicle manufacturers sell about 65 percent of their new vehicles to corporate fleet owners. This is important information. It suggests that, if societal demand for in-vehicle systems that enhance safety is to be stimulated, an important first step is to stimulate demand for these systems by fleet owners, who will eventually sell their vehicles to ordinary consumers. To achieve this, it is necessary to make fleet owners thoroughly familiar and comfortable with ITS technologies and to demonstrate to them the positive benefits of the technologies in reducing crash costs, fuel costs, and environmental impacts. The Australian TAC SafeCar project is aimed at meeting these objectives and should be monitored closely.
Finally, the majority of in-vehicle ITS systems entering the market are likely to be integrated into new vehicles rather than retrofitted to older vehicles. It is important, therefore, for the road safety community to assist the market for new vehicles in demanding the right kind of ITS technologies.
Research Needs
The review highlights a number of areas in which it is critical that research be conducted in order to better understand the potential benefits and disbenefits of ITS. Some of the more pressing areas in need of research are as follows.
Analytical Studies
There is a need to carefully analyse crash types in Australia and their distribution across different environments (e.g., urban, rural), road types and road user groups in order to quantify the crashes likely to be most affected by different ITS technologies, together with their outcomes and costs to the community. This point has been made previously by Cairney and Green (1999). Harrison and Fitzgerald (1999) have undertaken this activity for a limited number of crash types in Victoria as part of the previously mentioned T AC-sponsored SafeCar project. Preliminary estimates indicate that even a sub-set of the suite of technologies to be showcased and evaluated as part of this project (variable speed alerting, forward collision warning, seat-belt reminder system, breath alcohol detection and advisory system, mayday system, daytime running lights) can reduce trauma levels in Victoria by at least 30 percent, even with less than full market penetration of these systems. Further analytical modelling of this kind is urgently needed in order to quantify the potential safety benefits of other systems that are currently available and which will become commercially available in the near future.
Human Machine Interface
There is a need for research to develop criteria and procedures that will allow ITS human machine interfaces to be designed and evaluated on safety performance grounds. This would permit the development and promulgation of standards for ensuring that systems while in actual use meet a certain minimum level of safety. Developments in this area in Europe and in North America (in particular the Intelligent Vehicle Initiative) should be closely monitored and Australia, perhaps through its involvement in the SafeCar project, should contribute collaboratively to these activities.
Whilst there are currently no ratified standards for the safe design of the HMI for ITS applications, there are many human factors ITS design guidelines, procedures and draft standards which have been developed in North America, Europe and Japan. It is recommended that a compendium of relevant guidelines and research be compiled and synthesized which can be used to provide practical guidance for traffic engineers and vehicle manufacturers in Australia in the safe design of the HMI for in-vehicle and out-of-vehicle ITS technologies.
Behavioural Adaptation
Very little is known about how road users adapt temporarily and permanently to ITS technologies and how these changes in performance affect traffic safety. The Australian T AC SafeCar project will be very important in this respect as it will examine individual and interactive behavioural adaptation effects over a relatively long period of time for several in-vehicle ITS applications with significant potential safety benefits. Findings arising from this study should be monitored closely.
The Australian SafeCar project is, however, limited to the corporate fleet environment and further studies of the kind currently being undertaken in Sweden and the Netherlands are needed in Australia to examine temporary and long term behavioural adaptation to these systems by ordinary commuters, as the attitudes towards these systems and the patterns of useage by ordinary commuters are likely to be quite different from those of fleet drivers. It is recommended that a community trial be conducted in Victoria which draws on the experiences of both the Swedish and Dutch studies and relevant knowledge being derived from the T AC SafeCar project.
There are many in-vehicle ITS applications not being examined in the T AC SafeCar study that are available commercially or in prototype form with considerable safety potential. The more promising of these are variable speed limiting devices, electronic driver licences, and crash data recorders (black boxes). Others include driver vigilance monitoring devices, vision enhancement systems, and lane departure warning systems. It is recommended that on-road trials similar to the SafeCar project be undertaken in the near future to examine temporary and long term behavioural adaptation affects arising from exposure to these systems, particularly the first three mentioned.
The two most mature and commercially available ITS applications currently available in Australia and elsewhere around the world are adaptive cruise control and in-vehicle navigation systems. However, there is conflicting evidence regarding the potential safety benefits of these systems. Research is needed to determine how use of these systems by different high-risk road users affects driving performance and whether exposure to these systems results in increased exposure (through the creation of new trips) and, in the case of young drivers, risk homeostasis.
To the knowledge of the authors the safety benefits of manually-set speed alerting systems of the kind now available in most new Australian passenger vehicles have not yet been established. It is not known to what extent these devices are being used and in what way they are affecting speeding behaviour, suggesting a need for research in this area.
Human factors considerations appear not to have been incorporated to any great extent into the design of existing alcohol ignition interlocks. It is probably not surprising, therefore, that acceptance by recidivist drink drivers of traditional interlock devices has not been greater than it has been and that drivers with an alcohol problem tend to revert to their former drink-driving patterns once the interlock has been removed. Clearly, there is scope for research in this area.
High-risk and Vulnerable Road Users
Almost nothing is known about how different sub-groups of the driving population (e.g., young novice drivers, elderly drivers) vary in the way they adapt to ITS technologies temporarily and in the long term. Factors such as age, driving experience and driving style may influence the potential effectiveness of ITS technologies. Clearly it is important that, in any future studies of behavioural adaptation, particular attention is given to the differential effects that ITS may have on different road user groups.
To the knowledge of the authors there are almost no ITS applications currently available which are capable of preventing, or minimising the impact of, a collision between vehicles and vulnerable road users, although it is understood that there is some research and development work being undertaken in this area in Europe (e.g., by MIRA). There is a need to closely monitor developments in this area and to investigate in more detail what is currently being done.
There is an almost complete lack of literature available on motorcycle safety and ITS. There are many ITS technologies currently available and emerging which, with varying degrees of research and development, can be equipped to motorcycles. The issue of ITS and motorcycle safety is large one on its own which warrants further research. Australia is in a strong position to take leadership in this area.
Driver Acceptance of ITS
The need for a better understanding of peoples' attitudes and opinions about ITS applications, both before during and after they have experienced them, has been highlighted in this review as an important area for further research. Particularly notable is an almost complete lack of knowledge about the acceptance of ITS technologies by different sub-groups of the road user population such as motorcyclists, young drivers and older drivers. There is an urgent need for research in this area given the rapid rate at which ITS applications are becoming available.
Training
If future generations of drivers are trained solely in vehicles equipped to varying degrees with ITS technologies, they will not develop the skills associated with manual control that are required to drive manual vehicle or ITS vehicles in which automated systems fail. The issue of training and education for drivers of ITS-equipped vehicles is a complex one and there is an urgent need tp develop a co-ordinated training strategy based on research and consultation with government and industry that sets out future requirements for driver training.
Conclusion
ITS applications currently in existence, and being developed, have tremendous potential to reduce the incidence and severity of road crashes. To do so, however, human factors principles and knowledge must be incorporated into the design of these systems and they need to cater for the special needs of various road user groups. Failure to do so could seriously compromise the safety of the entire road transport system.