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Automation and the future of driver behavior
Safety Science 19 ( 1995) 237-244
Automation and the future of driver behavior Wiel Janssen”**, Marcel Wierdab, Richard van der Horst” “TN0 Institute for Perception, Kmnpweg 5, 3769 DE Soesterberg, The Netherlands “Traffic Research Centre, University of Groningen, P.O. Box 69, 9750 AB Harm. The Netherlands
Abstract
This paper sets out by identifying five plausible stages in the automation of the road traffic system, ranging from the introduction of part systems that support specific task components (navigation, collision avoidance) to full automation of roads and vehicles. It is then attempted to predict how drivers will respond to each successive stage of automation, and how this will become manifest in driver behavior. On the basis of this the paper assesses the safety consequences of each separate stage of automation.
1. Introduction
Automation - the allocation of tasks and responsibilities to a machine - is a potential way out of situations that human actors are not, or no longer, capable of handling. When applied to the road traffic system automation promises to reduce congestion both because of its potential to provide more optimal routing and to reduce intervehicle spacing in the longitudinal (and possibly also the lateral) dimension. And because of the latter - its potential to control vehicle interactions both longitudinally and laterally - it also promises more safety than the present system can ever hope to achieve. That automation will fulfill its promises is often taken for granted. It seems indeed selfevident that collision avoidance systems will avoid collisions, or that navigation support will save on mileage, because it reduces excess driving due to non-optimal routing. However, there is by now sufficient evidence to expect that things will be somewhat more complicated, and that much of this is due to the user’s tendency to respond to an automated system with behavioral changes that may actually be counterproductive to what automation should achieve. Thus, whenever parts of their task are automated, users will start to look for a new behavioral equilibrium that suits their own purposes, and the effects of this process of adaptation may come as more or less of a surprise to the system designer. * Correspondingauthor 0925.7535/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSD10925-7535(94)00025-5
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W. Janssen et al. /Safety Science I9 (1995) 237-244
Another aspect of automation that one should be aware of is that, like any other process of change, it probably creates new and qualitatively different problems per se. These may or may not be serious, but the point is that an effort is required to anticipate upon them before their seriousness can reasonably be judged. It is on the basis of these general insights, to which specific research findings will be added when appropriate, that we will consider the successive stages of automation of traffic as they are likely to evolve. First, the stages themselves must be identified and described.
2. Stages in the automation
of the road traffic system
Several authors (Johnston et al., 1988, 1990; Shladover, 1989) have sketched scenarios for the progressive automation of the road traffic system over time. In the view of these authors technology push and societal demands will interact and converge to a succession of stages in which more of the driving task is taken over by automatons at each next stage. This will in particular apply to higher-order parts of the network, that is, to interurban connections. If this is taken into consideration, and if we decide on a fairly coarse level of description rather than on a fine-grained analysis of which the details will be of doubtful validity, five stages seem sufficient to cover the continuum that ranges from the present-day system to full-fledged automation of major connections which may be foreseen sometime halfway the 21st century: Stage 1. Introduction of separate part-systems, starting with navigation support, to be followed by longitudinal (car-following) support. Stage 2. Introduction of integrated support systems that coordinate the actions of the available partial support systems. Stage 3. Extension of integrated systems with lateral support components, with respect to both traffic in adjacent lanes and the own vehicle per se. Stage 4. Introduction of so-called dedicated lanes for vehicles to be subjected to automatic execution of almost the entire driving task. Stage 5. Full-blown automation of all major connections.
3. Behavioral
adaptation
after automation
and its consequences
Before dealing with each separate stage we will present an inventory of effects that in a general sense can be expected to occur after some part of a task, which was formerly performed by humans, has been subjected to automation. The inventory is derived both from the general literature on human-machine interaction (Bainbridge, 1982) as well as from specific results originating in driver behavior research (Evans, 1985, 1991; Wilde, 1988). The following elements may be distinguished, where reference is in particular to consequences automation may have for safety: ( 1) Drivers will overall display somewhat riskier behavior after automation, that is, they tend to trade the increased safety that automation offers for higher mobility; this may include an increase in their exposure at the same (previous) cost of safety.
W. Janssen et al. /Safety Science 19 (1995) 237-244
239
(2) Drivers’ knowledge that they are guarded by the automaton leads to a decrease in their general level of alertness. (3) Drivers lose the skills for performing those components of the driving task that are taken over by the automaton, so that they can no longer apply these skills in the remaining cases in which they would be required. (4) Human error will not vanish after automation, but will shift to the design and maintenance of the automation. (5) Failure of the automaton will lead to more serious accidents than was formerly the case, that is, there will be a shift from accident frequency to accident severity. (6) Because severity rather than frequency determines public concern (the so-called “risk aversion” factor in societal risk analysis) an eventual improvement in safety will not be perceived for what it is, but rather for less. (7) Drivers whose task is (partially) automatized will experience a shift from risks taken voluntarily to risks imposed unvoluntarily, with a consequent demand for even lower objective risk levels than might already have been achieved. (8) Finally, the promises of increased safety and efficiency of the road traffic system will invite groups of drivers to take part in traffic who, for whatever reason, have stayed out of it thus far. By itself this will already increase exposure, and as such it is in fact another instance of the phenomenon that has already been mentioned under ( 1). In so far as these groups are composed of vulnerable or otherwise high-risk members, who used to stay home for exactly these reasons, an extra risk will be generated by their participation. All the factors enumerated here will affect the state of affairs after (parts of) the driving task will have been subjected to automation, and will contribute to the net effect on safety of this operation. When considering the separate stages in the progression of automation, as we will do in this paper, it will be of central concern which of the above effects will occur and to what degree. A fact of relevance in the present context is that automation of even the major parts of the road traffic system will not for a long time be complete and that it will not happen overnight. This means that not only will we have to deal with the afore-mentioned transition of individual drivers to some next stage of automation and its consequent processes of behavioral adaptation, but also with the fact that there will be transitions within the system (from automated to non-automated segments). Moreover, in the driving population a mix will exist with respect to levels of automation of individual vehicles. This is particularly difficult to treat, in terms of expected behavioral effects, since it involves interactions between drivers rather than individual behavior. Nevertheless, serious attention should be given to them when it comes to estimating net effects of automation.
4. Stage 1: Nagivation
and longitudinal
control
4.1. Navigation
In the order of 5% of mileage produced on current roadworks is estimated to be excess mileage (Jeffery, 198 1) . It is both due to non-optimal route planning and to drivers getting
240
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lost even after optimal preparation. Electronic navigation systems promise to eliminate excess mileage, as well as (at least) a proportional amount of road accidents. There are reasons to expect that these promises will not, or not fully, materialize. Road users having navigation support may reasonably be expected to change their behavior on two counts. First, rather than stay home and enjoy their extra 5% time off users may plan a trip to an extra destination. Second, navigation support will invite users to venture into territory that they did not dare go into previously for fear of getting lost. If this is really complex territory it may then not at all be improbable to get lost again, despite the support provided by the navigation system.
4.2. Longitudinal control
Systems for collision avoidance, intelligent cruise control, cooperative driving, etc., are presently in advanced stages of development. There appears to be no discernible ambition here towards actually taking away ultimate decision power from the driver. For example, a European collision avoidance concept developed within the DRIVE-Project has the accelerator function as an active control when the vehicle gets too close to the preceding vehicle, while allowing the driver to overrule the pedal by an action of his own (Godthelp, 1986; Janssen and Nilsson, 1990). This being the case, drivers who are armed with longitudinal supports have ample opportunity to adapt their general driving style in essentially counterproductive ways while still being helped out of critical situations by the system. For example, in studies on the possible design of collision avoidance systems, it was often observed that following leading vehicles at very short distance was indeed drastically reduced, but that drivers also showed a distinct tendency towards overall higher driving speeds (Janssen and Nilsson, 1990). The issue thus appears to be how one should design collision avoidance systems - and also other systems that support longitudinal control - that suffer minimally from these compensatory effects while of course fulfilling their primary aim.
4.3. Transition effects
That there may exist a mix of vehicles in this stage with respect to whether they possess navigational support and/or some form of longitudinal support is not too worrying. Both these partial supports, when engaged, do not directly make the traffic environment more critical for others. What is worrying, however, is that the less careful driving style that these provisions may encourage will put others at higher risk. Thus, those who have not got the supports not only do not have the benefits of these, but may actually suffer from the behavioral adaptations of those who have them. A transition that every user of partial support systems must make is from being a novice to becoming an old hand. It is at present not known how this learning process takes place. It is therefore too early to speculate about whether, and how, people should be taught the use of advanced technology as part of their education as a driver.
W. Junssen et al. /Safety Science 19 (1995) 237-244
5. Stage 2: Integrated
241
systems as co-drivers
The demand for integrated systems is already heard at this moment - for example, there is considerable effort within DRIVE put into it -, and it will become stronger the more it will be realized that it is worthwhile to treat automated support within the vehicle as a concept of its own rather than something that will emerge naturally from a collection of isolated components. An extra impetus will be added to this demand by the growing tendency to use vehicles as “extended offices”, introducing information streams that do not pertain to the driving task properly. There is then a need to think about ways to handle this potential information overload in a coherent manner. The core of an integrated support system is generally conceived to be an intelligence that supervises and filters the stream of information to the driver, and that prioritizes support in accordance with the prevailing configuration on the road and with the driver’s momentary workload (Michon, 1992). As with the separate components of Stage 1 the intention is not, in existing projects we know of, to automatize the driver away, but to suggest actions to him or to make an overrulable start with these by means of active controls. Given that drivers will have this intelligent co-driver in their vehicle, how will they respond to the type of support that is offered? The behavioral adaptation effects that already occurred in Stage 1 as a response to the modules for navigation and longitudinal control will continue into Stage 2. What is new, however, is the highly increased power of the intelligent co-driver to act as a watchdog over the driver’s sloppiness in order to correct him in appropriate ways whenever necessary. It needs no great imagination to predict that this will be detrimental to drivers’ overall level of alertness, and that because of this solutions will be required from the intelligent co-driver to problems that did not even exist before.
6. Stage 3: Extension
towards lateral control
The reason why we have put the introduction of lateral control support only in Stage 3 of automation, even after otherwise integrated in-vehicle support systems have appeared, is that we feel that substantial changes in the road infrastructure itself will now be needed to accommodate any further automation. No longer will stand-alone and/or inter-vehicle provisions suffice to get the system going. Thus, although it could theoretically be done by sending course information from an in-vehicle sensor straight to the steering wheel, it will most likely be by external course and position monitoring devices that lateral control will be exerted (e.g., Shladover et al., 199 1) . The potential gain of automatic lateral control is, first, in capacity. If lanes could be half their current width, then throughput would double from this effect alone. The other gain would be in safety, by assisting in keeping individual vehicles on the road that threaten to go astray. As in the previous stages of automation the issue will most likely not be whether to remove the driver from the loop completely, but rather in what - overrulable - way the driver should be supported. And, of course, lateral control would have to be incorporated in the already existing integral support system and its potential contributions at any moment scrutinized and prioritized along with those of other modules.
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With lateral control added, the functions that lend themselves to be subjected to a certain degree of automation will be exhausted. It will be in this stage that drivers will realize that automatons are keeping an eye on them in all aspects of the driving task. Next to continuing behavioral adaptation and loss in overall alertness, this will cause the element of voluntary versus involuntary risk to become more prominent than it has been thus far. Thus, the perception that external agents are now taking care of a considerable part of their activities, and that this puts constraints on how they are allowed to handle situations themselves, will lead drivers to no longer accept the risk levels that they previously accepted voluntarily. This will then create an extra demand for safety that the Stage 3-automated traffic system will have to fulfill. The most likely response to this will be a call for more automation, and this time the only remaining option is to grant full power to the machine.
7. Stage 4: Dedicated lanes
As an intermediate step to the ultimate stage of automation we may expect that separate lanes will be built-probably by reshaping existing “fast” (lefthand) lanes-to which only vehicles have access in which decision power has largely been allocated to the machine. The driver’s navigation task will be reduced to informing the system of a desired destination, and longitudinal and lateral interactions with surrounding vehicles will be regulated by direct interventions originating from a non-overrulable intelligence. Assuming that technology will be capable of finding and implementing the appropriate intervention in each and every conceivable configuration - which by itself seems not totally guaranteed - there will then be much less opportunity for drivers to change their behavior in counterproductive ways. Testing the system to its limits may become a sport for some time, and there should be anticipation upon this phenomenon, but by and large acceptance of full automation should by this time be so general that technology may be applied to constrain what a driver can do to any desired minimum. Does this mean that unsafety will finally be eliminated from the system? It is hard to believe that this is actually going to be the case. As the required technology gets more complex, it will also get more vulnerable to errors of design and maintenance. When a technical malfunctioning occurs because of either of these we will then experience monumental pile-ups, both because situations have become intrinsically more critical and because drivers have lost the ability to deal with them. The consequent shift from frequent accidents with one or two victims to relatively rare, but much more serious ones will then become a case for public concern. Another effect that will become of real significance in this stage is that of transitions within the road network from the fully automated lanes to less or non-automated areas. Drivers who have to make this transition will experience the following: ( 1) A sudden demand for alertness at the transition point, after a ride on the dedicated lane that hardly demanded any attention at all. (2) After-effects of the supposedly extreme speed of travelling on the dedicated lane, with a resulting choice of driving speed on the lower-order part of the network that will be higher than intended.
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243
8. Stage 5: Full automation In what is to be seen as the final stage of automation of the road connections will consist of dedicated lanes only. From the point effects, the introduction of this final stage is relatively uninteresting, already have occurred in the previous stage. Nevertheless, they significance.
traffic system all major of view of behavioral since most effects will will continue to be of
9. What, then, about automation? It would be wrong to conclude from the previous pages that our view of the automation of road traffic is essentially negative. What we have hoped to make clear is that road users will not remain passive under automation. They will most likely respond with behavior that makes a safety gain less than expected or lets it emerge as something else, a gain in mobility in particular. It is only by acknowledging this that one can get into a state of mind required to consider further interesting questions, like whether it is possible to design support systems that suffer less than others from the behavioral adaptation effects they evoke (it is), and whether it is still worthwhile to continue research into the possibilities of affecting traffic safety by other than purely technological means (it is). What we have also tried to indicate is that automation, apart from the effects of induced behavioral adaptation, sometimes creates new problems per se to which explicit attention had better be given beforehand. Together this would seem to come down to a realistic, rather than a negative view of what to expect from the automation of road traffic. We are convinced that realism is more appropriate than the unwarranted euphoria that so often seems associated with the marvels of new technology.
Acknowledgement This paper is prepared from a more extensive report commissioned by the Netherlands Ministry of Transport and Public Works (Janssen, Wierda and van der Horst, 1992).
References Bainbridge, L., 1982. Ironies of automation. Automatica, I9( 6). Evans, L., 1985. Human behaviour feedback and traffic safety. Human Factors 27: 55.5-576. Evans, L., 1991. Traffic Safety and the Driver. Van Nostrand Reinhold, New York. Godthelp, .I., 1986. Elektronische beinvlc-edingssystemen in het wegverkeer; een verkenning van mogelijkheden. Rapport IZF 1986 C-10, Soesterberg: Instituut voor Zintuigfysiologie TNO. Janssen, W.H. and Nilsson, L., 1990. An experimental evaluation of in-vehicle collision avoidance systems. DRIVE-Deliverable GIDS/MAN 2.
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Janssen, W.H., Wierda, M. and Horst, A.R.A. van der, 1992. Automatisering van de rijtaak en gebruikersgedrag: Een inventarisatie en research-agenda. Rapport IZF 1992 C-16, Soesterberg: Instituut voor Zintuigfysiologie TNO. Jeffery, D.J., 1981. Ways and means for improving driver route guidance. Crowthome: TRRL Report 1016. Johnston, R.A., Sperling, D. and Craig, P.P., 1988. Freeway automation policy issues. San Francisco: SAE Techn. Paper Series No. 881211, Future Trans. Conf. Johnston, R.A., De Luchi, M.A., Sperling, D. and Craig, P.P., 1990. Automating urban freeways: Policy research agenda. J. Transport. Eng., 16: 442-460. Michon, J.A. (Ed.), 1992. Generic Intelligent Driver Support. Taylor and Francis, London. Shladover, S.E., 1989. Roadway automation technology: Research needs. Washington DC. TRB Preprint Paper No. 880208. Shladover. SE. et al., 1991. Automatic vehicle control developments in the PATH program. IEEE Trans. on Vehicular Technology 40: 114-130. Wilde, G.J.S., 1988. Risk homeostasis theory: propositions, deductions and discussion of recent commentaries. Ergonomics,
3 I : 441468.
Automation and the future of driver behavior Wiel Janssen”**, Marcel Wierdab, Richard van der Horst” “TN0 Institute for Perception, Kmnpweg 5, 3769 DE Soesterberg, The Netherlands “Traffic Research Centre, University of Groningen, P.O. Box 69, 9750 AB Harm. The Netherlands
Abstract
This paper sets out by identifying five plausible stages in the automation of the road traffic system, ranging from the introduction of part systems that support specific task components (navigation, collision avoidance) to full automation of roads and vehicles. It is then attempted to predict how drivers will respond to each successive stage of automation, and how this will become manifest in driver behavior. On the basis of this the paper assesses the safety consequences of each separate stage of automation.
1. Introduction
Automation - the allocation of tasks and responsibilities to a machine - is a potential way out of situations that human actors are not, or no longer, capable of handling. When applied to the road traffic system automation promises to reduce congestion both because of its potential to provide more optimal routing and to reduce intervehicle spacing in the longitudinal (and possibly also the lateral) dimension. And because of the latter - its potential to control vehicle interactions both longitudinally and laterally - it also promises more safety than the present system can ever hope to achieve. That automation will fulfill its promises is often taken for granted. It seems indeed selfevident that collision avoidance systems will avoid collisions, or that navigation support will save on mileage, because it reduces excess driving due to non-optimal routing. However, there is by now sufficient evidence to expect that things will be somewhat more complicated, and that much of this is due to the user’s tendency to respond to an automated system with behavioral changes that may actually be counterproductive to what automation should achieve. Thus, whenever parts of their task are automated, users will start to look for a new behavioral equilibrium that suits their own purposes, and the effects of this process of adaptation may come as more or less of a surprise to the system designer. * Correspondingauthor 0925.7535/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSD10925-7535(94)00025-5
238
W. Janssen et al. /Safety Science I9 (1995) 237-244
Another aspect of automation that one should be aware of is that, like any other process of change, it probably creates new and qualitatively different problems per se. These may or may not be serious, but the point is that an effort is required to anticipate upon them before their seriousness can reasonably be judged. It is on the basis of these general insights, to which specific research findings will be added when appropriate, that we will consider the successive stages of automation of traffic as they are likely to evolve. First, the stages themselves must be identified and described.
2. Stages in the automation
of the road traffic system
Several authors (Johnston et al., 1988, 1990; Shladover, 1989) have sketched scenarios for the progressive automation of the road traffic system over time. In the view of these authors technology push and societal demands will interact and converge to a succession of stages in which more of the driving task is taken over by automatons at each next stage. This will in particular apply to higher-order parts of the network, that is, to interurban connections. If this is taken into consideration, and if we decide on a fairly coarse level of description rather than on a fine-grained analysis of which the details will be of doubtful validity, five stages seem sufficient to cover the continuum that ranges from the present-day system to full-fledged automation of major connections which may be foreseen sometime halfway the 21st century: Stage 1. Introduction of separate part-systems, starting with navigation support, to be followed by longitudinal (car-following) support. Stage 2. Introduction of integrated support systems that coordinate the actions of the available partial support systems. Stage 3. Extension of integrated systems with lateral support components, with respect to both traffic in adjacent lanes and the own vehicle per se. Stage 4. Introduction of so-called dedicated lanes for vehicles to be subjected to automatic execution of almost the entire driving task. Stage 5. Full-blown automation of all major connections.
3. Behavioral
adaptation
after automation
and its consequences
Before dealing with each separate stage we will present an inventory of effects that in a general sense can be expected to occur after some part of a task, which was formerly performed by humans, has been subjected to automation. The inventory is derived both from the general literature on human-machine interaction (Bainbridge, 1982) as well as from specific results originating in driver behavior research (Evans, 1985, 1991; Wilde, 1988). The following elements may be distinguished, where reference is in particular to consequences automation may have for safety: ( 1) Drivers will overall display somewhat riskier behavior after automation, that is, they tend to trade the increased safety that automation offers for higher mobility; this may include an increase in their exposure at the same (previous) cost of safety.
W. Janssen et al. /Safety Science 19 (1995) 237-244
239
(2) Drivers’ knowledge that they are guarded by the automaton leads to a decrease in their general level of alertness. (3) Drivers lose the skills for performing those components of the driving task that are taken over by the automaton, so that they can no longer apply these skills in the remaining cases in which they would be required. (4) Human error will not vanish after automation, but will shift to the design and maintenance of the automation. (5) Failure of the automaton will lead to more serious accidents than was formerly the case, that is, there will be a shift from accident frequency to accident severity. (6) Because severity rather than frequency determines public concern (the so-called “risk aversion” factor in societal risk analysis) an eventual improvement in safety will not be perceived for what it is, but rather for less. (7) Drivers whose task is (partially) automatized will experience a shift from risks taken voluntarily to risks imposed unvoluntarily, with a consequent demand for even lower objective risk levels than might already have been achieved. (8) Finally, the promises of increased safety and efficiency of the road traffic system will invite groups of drivers to take part in traffic who, for whatever reason, have stayed out of it thus far. By itself this will already increase exposure, and as such it is in fact another instance of the phenomenon that has already been mentioned under ( 1). In so far as these groups are composed of vulnerable or otherwise high-risk members, who used to stay home for exactly these reasons, an extra risk will be generated by their participation. All the factors enumerated here will affect the state of affairs after (parts of) the driving task will have been subjected to automation, and will contribute to the net effect on safety of this operation. When considering the separate stages in the progression of automation, as we will do in this paper, it will be of central concern which of the above effects will occur and to what degree. A fact of relevance in the present context is that automation of even the major parts of the road traffic system will not for a long time be complete and that it will not happen overnight. This means that not only will we have to deal with the afore-mentioned transition of individual drivers to some next stage of automation and its consequent processes of behavioral adaptation, but also with the fact that there will be transitions within the system (from automated to non-automated segments). Moreover, in the driving population a mix will exist with respect to levels of automation of individual vehicles. This is particularly difficult to treat, in terms of expected behavioral effects, since it involves interactions between drivers rather than individual behavior. Nevertheless, serious attention should be given to them when it comes to estimating net effects of automation.
4. Stage 1: Nagivation
and longitudinal
control
4.1. Navigation
In the order of 5% of mileage produced on current roadworks is estimated to be excess mileage (Jeffery, 198 1) . It is both due to non-optimal route planning and to drivers getting
240
W. Janssen et al. /Safety Science I9 (I 995) 237-244
lost even after optimal preparation. Electronic navigation systems promise to eliminate excess mileage, as well as (at least) a proportional amount of road accidents. There are reasons to expect that these promises will not, or not fully, materialize. Road users having navigation support may reasonably be expected to change their behavior on two counts. First, rather than stay home and enjoy their extra 5% time off users may plan a trip to an extra destination. Second, navigation support will invite users to venture into territory that they did not dare go into previously for fear of getting lost. If this is really complex territory it may then not at all be improbable to get lost again, despite the support provided by the navigation system.
4.2. Longitudinal control
Systems for collision avoidance, intelligent cruise control, cooperative driving, etc., are presently in advanced stages of development. There appears to be no discernible ambition here towards actually taking away ultimate decision power from the driver. For example, a European collision avoidance concept developed within the DRIVE-Project has the accelerator function as an active control when the vehicle gets too close to the preceding vehicle, while allowing the driver to overrule the pedal by an action of his own (Godthelp, 1986; Janssen and Nilsson, 1990). This being the case, drivers who are armed with longitudinal supports have ample opportunity to adapt their general driving style in essentially counterproductive ways while still being helped out of critical situations by the system. For example, in studies on the possible design of collision avoidance systems, it was often observed that following leading vehicles at very short distance was indeed drastically reduced, but that drivers also showed a distinct tendency towards overall higher driving speeds (Janssen and Nilsson, 1990). The issue thus appears to be how one should design collision avoidance systems - and also other systems that support longitudinal control - that suffer minimally from these compensatory effects while of course fulfilling their primary aim.
4.3. Transition effects
That there may exist a mix of vehicles in this stage with respect to whether they possess navigational support and/or some form of longitudinal support is not too worrying. Both these partial supports, when engaged, do not directly make the traffic environment more critical for others. What is worrying, however, is that the less careful driving style that these provisions may encourage will put others at higher risk. Thus, those who have not got the supports not only do not have the benefits of these, but may actually suffer from the behavioral adaptations of those who have them. A transition that every user of partial support systems must make is from being a novice to becoming an old hand. It is at present not known how this learning process takes place. It is therefore too early to speculate about whether, and how, people should be taught the use of advanced technology as part of their education as a driver.
W. Junssen et al. /Safety Science 19 (1995) 237-244
5. Stage 2: Integrated
241
systems as co-drivers
The demand for integrated systems is already heard at this moment - for example, there is considerable effort within DRIVE put into it -, and it will become stronger the more it will be realized that it is worthwhile to treat automated support within the vehicle as a concept of its own rather than something that will emerge naturally from a collection of isolated components. An extra impetus will be added to this demand by the growing tendency to use vehicles as “extended offices”, introducing information streams that do not pertain to the driving task properly. There is then a need to think about ways to handle this potential information overload in a coherent manner. The core of an integrated support system is generally conceived to be an intelligence that supervises and filters the stream of information to the driver, and that prioritizes support in accordance with the prevailing configuration on the road and with the driver’s momentary workload (Michon, 1992). As with the separate components of Stage 1 the intention is not, in existing projects we know of, to automatize the driver away, but to suggest actions to him or to make an overrulable start with these by means of active controls. Given that drivers will have this intelligent co-driver in their vehicle, how will they respond to the type of support that is offered? The behavioral adaptation effects that already occurred in Stage 1 as a response to the modules for navigation and longitudinal control will continue into Stage 2. What is new, however, is the highly increased power of the intelligent co-driver to act as a watchdog over the driver’s sloppiness in order to correct him in appropriate ways whenever necessary. It needs no great imagination to predict that this will be detrimental to drivers’ overall level of alertness, and that because of this solutions will be required from the intelligent co-driver to problems that did not even exist before.
6. Stage 3: Extension
towards lateral control
The reason why we have put the introduction of lateral control support only in Stage 3 of automation, even after otherwise integrated in-vehicle support systems have appeared, is that we feel that substantial changes in the road infrastructure itself will now be needed to accommodate any further automation. No longer will stand-alone and/or inter-vehicle provisions suffice to get the system going. Thus, although it could theoretically be done by sending course information from an in-vehicle sensor straight to the steering wheel, it will most likely be by external course and position monitoring devices that lateral control will be exerted (e.g., Shladover et al., 199 1) . The potential gain of automatic lateral control is, first, in capacity. If lanes could be half their current width, then throughput would double from this effect alone. The other gain would be in safety, by assisting in keeping individual vehicles on the road that threaten to go astray. As in the previous stages of automation the issue will most likely not be whether to remove the driver from the loop completely, but rather in what - overrulable - way the driver should be supported. And, of course, lateral control would have to be incorporated in the already existing integral support system and its potential contributions at any moment scrutinized and prioritized along with those of other modules.
242
W. Janssen et al. /Safety Science 19 (1995) 237-244
With lateral control added, the functions that lend themselves to be subjected to a certain degree of automation will be exhausted. It will be in this stage that drivers will realize that automatons are keeping an eye on them in all aspects of the driving task. Next to continuing behavioral adaptation and loss in overall alertness, this will cause the element of voluntary versus involuntary risk to become more prominent than it has been thus far. Thus, the perception that external agents are now taking care of a considerable part of their activities, and that this puts constraints on how they are allowed to handle situations themselves, will lead drivers to no longer accept the risk levels that they previously accepted voluntarily. This will then create an extra demand for safety that the Stage 3-automated traffic system will have to fulfill. The most likely response to this will be a call for more automation, and this time the only remaining option is to grant full power to the machine.
7. Stage 4: Dedicated lanes
As an intermediate step to the ultimate stage of automation we may expect that separate lanes will be built-probably by reshaping existing “fast” (lefthand) lanes-to which only vehicles have access in which decision power has largely been allocated to the machine. The driver’s navigation task will be reduced to informing the system of a desired destination, and longitudinal and lateral interactions with surrounding vehicles will be regulated by direct interventions originating from a non-overrulable intelligence. Assuming that technology will be capable of finding and implementing the appropriate intervention in each and every conceivable configuration - which by itself seems not totally guaranteed - there will then be much less opportunity for drivers to change their behavior in counterproductive ways. Testing the system to its limits may become a sport for some time, and there should be anticipation upon this phenomenon, but by and large acceptance of full automation should by this time be so general that technology may be applied to constrain what a driver can do to any desired minimum. Does this mean that unsafety will finally be eliminated from the system? It is hard to believe that this is actually going to be the case. As the required technology gets more complex, it will also get more vulnerable to errors of design and maintenance. When a technical malfunctioning occurs because of either of these we will then experience monumental pile-ups, both because situations have become intrinsically more critical and because drivers have lost the ability to deal with them. The consequent shift from frequent accidents with one or two victims to relatively rare, but much more serious ones will then become a case for public concern. Another effect that will become of real significance in this stage is that of transitions within the road network from the fully automated lanes to less or non-automated areas. Drivers who have to make this transition will experience the following: ( 1) A sudden demand for alertness at the transition point, after a ride on the dedicated lane that hardly demanded any attention at all. (2) After-effects of the supposedly extreme speed of travelling on the dedicated lane, with a resulting choice of driving speed on the lower-order part of the network that will be higher than intended.
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8. Stage 5: Full automation In what is to be seen as the final stage of automation of the road connections will consist of dedicated lanes only. From the point effects, the introduction of this final stage is relatively uninteresting, already have occurred in the previous stage. Nevertheless, they significance.
traffic system all major of view of behavioral since most effects will will continue to be of
9. What, then, about automation? It would be wrong to conclude from the previous pages that our view of the automation of road traffic is essentially negative. What we have hoped to make clear is that road users will not remain passive under automation. They will most likely respond with behavior that makes a safety gain less than expected or lets it emerge as something else, a gain in mobility in particular. It is only by acknowledging this that one can get into a state of mind required to consider further interesting questions, like whether it is possible to design support systems that suffer less than others from the behavioral adaptation effects they evoke (it is), and whether it is still worthwhile to continue research into the possibilities of affecting traffic safety by other than purely technological means (it is). What we have also tried to indicate is that automation, apart from the effects of induced behavioral adaptation, sometimes creates new problems per se to which explicit attention had better be given beforehand. Together this would seem to come down to a realistic, rather than a negative view of what to expect from the automation of road traffic. We are convinced that realism is more appropriate than the unwarranted euphoria that so often seems associated with the marvels of new technology.
Acknowledgement This paper is prepared from a more extensive report commissioned by the Netherlands Ministry of Transport and Public Works (Janssen, Wierda and van der Horst, 1992).
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