Speed support through the intelligent vehicle

Perspective, estimated effects and implementation aspects
Morsink (SWOV), P.; Goldenbeld (SWOV), Ch.; Dragutinovic (SWOV/TU Delft), N.; Marchau (TU Delft), V.; Walta (TU Delft), L.; Brookhuis (TU Delft), K.
This report links different types of information about the position and perspective of speed management measures related to intelligent vehicles. Here a vehicle is defined as 'intelligent' if it obtains information from the environment (other vehicles, the infrastructure) and shares information with the environment, in order to assist the driver. The report presents scientific evidence of the predicted effects of promising intelligent vehicle systems for speed support. The evidence is based on state-of-the-art scientific knowledge, primarily dealing with safety, but also involving the other policy areas traffic efficiency and the environment. The report also gives an overview of key factors in the process of realizing the expected effects in practice. This is about uncertainties regarding reported effects, and about the question of effective deployment. For the latter, the report discusses the position of the different stakeholders, and potentially successful implementation strategies. Based on further insight into these key aspects, the report makes suggestions for further research and policymaking. Intelligent vehicle measures within speed management Speed management is a central theme in traffic management, aiming to optimize traffic in terms of safety, efficiency and the environment, by reducing speeding and speed differences in traffic. It has been estimated that in about 30% of fatal road accidents excessive speed is involved, making speed one of the crucial factors in road safety. There are different types of speed measures: infrastructural engineering, education, enforcement (the 3 E's), ánd vehicles. Preferably these types of measures interact well as part of a general road safety policy. The Dutch Sustainable Safety vision provides a framework for such a policy, with management of vehicle speed as one of its fundamental issues, and with a good perspective for the integration of traditional (i.e. the 3 E's) and new measures (e.g. based on intelligent vehicles). According to Sustainable Safety, speed limits are the core of the speed management system, and they must be safe and credible (matching infrastructural design and road network layout). Speed limits are preferably dynamic, instead of static, so that they are adjusted to changing traffic circumstances, such as weather, traffic density, pollution levels, and incidents. And last but not least, road users have to be well-informed about the limits. Intelligent vehicles can perform tasks that conventional measures cannot do at all, or do less efficiently. First of all, they are an addition to current speed measures by helping to deploy the favoured speed limit system and increase the compliance with it. Furthermore, in-vehicle technology can support the driver in choosing an appropriate speed at all times and places, and in highly changing, specific conditions, that can not be accounted for in speed limits. Effect estimates have been described for four types of systems that contain (some of) these functionalities: various forms of Intelligent Speed Assistance (ISA), Advanced Cruise Control (ACC), Vision Enhancement Systems (VES), and black boxes. Much more literature was available for ISA and ACC than for the other two systems. Results of different types of studies were considered, noting that the evaluation of the systems in real traffic is still rare. Besides the difference in the amount of available literature, there are also differences in the sizes and types of effects found in different studies. Therefore only indications can be given of what may eventually be achieved. Effect estimates for ISA show the best results, though varying in type of feedback and intervention level ( informing, warning, intervening, automatic control) and speed limit type (static, dynamic). ISA enables drivers to always have direct access to speed limit information in their car. The informing and warning types (also called SpeedAlert) actually can be seen as an additional feature of route navigation systems, and they recently started to be introduced on the market. Static informing ISA could possibly reduce fatal crashes over the whole road network by almost 20%. Speeding offences due to driver’s mistake or misjudgment are expected to drop considerably with these systems. For enforcement they can add to the credibility and effectiveness of speed checks. The best results, a reduction of fatal crashes with more than 50%, are expected from mandatory installation of dynamic automatic controlling ISA, in all cars, with no possibility to overrule. The predicted effects of other types are on levels between the two described here. Further compliance with the limits, especially for drivers who speed deliberately, can be achieved by the more restrictive ISA types. There are also relevant indications of a reduction in fuel consumption and harmful emissions (reductions between 4 and 11% have been reported for CO2, NOX, and HC), and of increased traffic efficiency, although research on this topic is still limited. Most ACC studies show a significant decrease of speed variations due to ACC, leading to stronger indications for environmental benefits (decrease of fuel consumption and emissions) than for safety and traffic efficiency. The best road safety results of ACC, maximum accident reductions of more than 10%, are expected on motorways, in non-congested traffic, and in good weather. ACC effects on other road types needs to be further assessed, as well as the effects of different time headway settings. More positive effects are predicted for the next generation ACC, which will be more designed to detect hazards, e.g. by car-to-car communication, and to operate in congestion prone traffic. A combination of ISA and ACC may also be a good option. Where ISA reduces the mean speed and speeding, ACC may add to the system by reducing tailgaiting and speed variations. If individual cars supply their speed data to a traffic manager (e.g. through floating car data), it could give more reliable traffic information to drivers and an optimum speed advice for the given traffic situation. The effect estimates of ISA and ACC assume 100% equipment rates, and do not take into account possible side effects, such as behavioural adaptation that may reduce the predicted effects. Risk compensation may e.g. lead to closer following; reduced attention may lead to slower reactions; overconfidence may result in insufficiently observing traffic circumstances; speed limitation may invoke frustration in the driver himself and frustration in following non-equipped traffic (possibly causing worse merging), as well as large speed differences between equipped and non-equipped vehicles. ACC usage on rural roads may lead to worse overtaking behaviour. More research should be done to assess the impact of these factors, e.g. with large field operational tests. Based on qualitative observations, black boxes would give a considerable decrease of speeding. It also provides a possibility to give behavioural feedback to the driver, both positive and negative. VES has been treated as an example of Advanced Driver Assistance Systems (ADAS) which are not directly aimed at speed support, but with some reported effects on speed behaviour. The improved visibility offered by the system results in a higher mean speed in low visibility conditions. It should be further investigated what this means for the change of risk. Deployment of Intelligent Speed Assistance The largest safety effects and substantial effects in other fields are expected from ISA. To actually meet these expectations, adequate deployment is needed. This requires considerable effort, since so far there has only been little market activity. However, the basic technology is readily available and differences between stakeholder positions slow down the decision-making on ISA implementation. All this makes ISA an interesting subject for to investigating deployment processes. Public authorities, the industry and consumers/drivers are the main stakeholders for ISA deployment, and good cooperation between them is necessary for successful implementation of ISA. More insight in the position (acceptance and preferences) of these stakeholder groups has been obtained, showing that they are not fully compatible yet, which requires further attention. On the other hand, e.g. the differences in opinions about safety are not that big, and not expected to seriously jeopardize further improvements and implementation. All stakeholders show a general preference for systems that leave most freedom to the driver: i.e. voluntary warning ISA is most accepted and preferred among the stakeholders. The most promising ISA type in terms of expected safety effects, i.e. a mandatory automatically controlling form of ISA, is the overall least preferred form. Interestingly, it does not follow that mandatory introduction lacks substantial public support, as has been shown by a major survey among European car drivers in 2002. On the one hand, consumers/drivers begin to show resistance when personal freedom is at stake. On the other hand, there is considerable support when drivers think about effective measures, particularly if mandatory ISA were restricted to 30 or 50 km roads in urban areas, if it would operate within credible speed limits, and if the financial consequences are not too large. ISA acceptance among drivers could be further increased if the system helps to prevent speeding fines, saves fuel, and if there is an influential early adopter group that will serve as example for others. Public authorities are most interested in a cost-efficient contribution of the systems to policy goals. For road authorities the system's functional and technical reliability is important. Furthermore, they do not appreciate the general association of ISA with a mandatory, closed system of speed control. Therefore, the term SpeedAlert has been introduced for informing and warning ISA types to stress the importance of leaving full control of driving speed to the driver. While public authorities and consumers/drivers value safety as the most important outcome, for the industry factors relating to costs and financial risk are important considerations. Future research into stakeholder opinions regarding ISA should concentrate on an unambiguous methodology for the assessment of preferences of individual stakeholders (rather than of the average stakeholder), including changes in preferences over time. There should also be a strategy for research towards stakeholder acceptance, that deals with communication, socio-political developments, and past successes or failures. An important aspect in creating a serious user demand for ISA will be to create an awareness of the benefits for the individual driver, combined with the collective interests for society as a whole. Upgrading current vehicles to intelligent vehicles may help to bridge this gap. Combined functionalities may result in an integrated driver assistance system, based on existing technology and supported by new technological developments. It can help to drive safely, avoid speeding tickets, optimize travel times and route planning, and drive in a comfortable and economic way. This combination of functions may make it easier to address the individual driver since he will get a more straightforward return on investment. Upgrading of the vehicle may also add to the product image and commercial attraction of the vehicle, while at the same time contributing to public goals. Effective deployment of ISA requires good coordination, both at the national and at the international level. Central governments are in a good position to lead the coordination process. In most countries, they have the responsibility for the quality of the overall traffic and transport system. Furthermore, they have the overview of what is available in the market, how various applications can interact, and how ISA can be tuned to other speed management measures. Besides, ready-to-roll market models are rare. A good connection should be established with other national governments, the European Commission, and with local governments. Potentially successful implementation strategies have been explored, searching for a good balance between market-orientated parties and government parties. There will be different accents in government roles in case of mainly market-driven or mainly government-driven implementation paths. In the first case, governments should focus on supporting the process by promotion and education. They should also watch over the balance between individual and collective interests, regulating and standardising where necessary, and they should establish a legal framework to deal with liability issues. Furthermore, they can facilitate progress by further developing digital speed maps (improving the quality, making it accessible), by being a partner in research and demonstration projects, and by offering financial incentives. In the second case, dealing with less popular, though effective systems, the government should take the initiative in raising support. Better insight in the policy making process can directly influence the implementation scenarios. An innovative way of public policymaking for ISA has been described, dealing with uncertainties that surround a large scale implementation of ISA. Traditional incremental policy approaches can remain passive in response to these uncertainties, allowing developments to be largely determined by the flow of market forces. Several experts argue that policymaking should be more active and adaptive, allowing an early implementation, with the policy being adapted over time. An example has been described in which first a basic policy was defined, uncertainties were translated to vulnerabilities (which can make a policy fail), and signposts were installed to monitor their status and policy progress. Where needed, defensive or corrective actions would be performed, or the policy would be reassessed. The perspective of adaptive policymaking is promising, but some legal, political and analytic barriers still need to be overcome, before it can be put into practice. Further specification and testing of the approach for ISA should focus on systematic identification of the vulnerabilities. Scenario and simulation gaming may be used to compare adaptive policymaking to more traditional policymaking approaches. In this process scenarios should be envisaged in which in-vehicle ITS for speed support becomes increasingly important, co-existing with other measures and at the same time adding efficiency, and on the longer term possibly replacing some of the more traditional measures. Finally In general it has been shown that the role of intelligent vehicle measures in speed management can gradually become more prominent, in combination with traditional measures (infrastructural engineering, education, enforcement). Although large potential effects are forecast, and technological developments proceed, it is still uncertain if and when the systems will find a position among traditional measures, and make their promising perspectives a reality. However, relevant insight has been gathered, that can be used for further steps in research and deployment of the most promising systems. For research, it is important to improve the reliability of effect estimates and to obtain better understanding of the deployment processes. This should result in more reliable predictions of penetration rates of the systems on the short and on the longer term. Eventually, this may lead to improved impact assessment, providing more knowledge to predict contributions of the systems to policy goals (such as in the Mobility Policy Document). For deployment, a good basis would be the establishment of a generally accepted framework for ITS policy at the international, national and local level. All relevant stakeholders should participate, aiming at mutual cooperation. A road safety agreement for the implementation of ITS, with special focus on ISA, could be an appropriate first step; in any case in the Netherlands. Such an agreement may clarify and reduce uncertainties about the pace and direction of developments. Concurrent with such an initiative, first steps could be made to set up an adaptive policy for ISA.
Report number
SWOV, Leidschendam

SWOV publication

This is a publication by SWOV, or that SWOV has contributed to.