Learning headway estimation in driving

OBJECTIVE: The main purpose of the present study was to examine to what extent the ability to attain a required headway of 1 or 2 s can be improved through practical driving instruction under real traffic conditions and whether the learning is sustained after a period during which there has been no controlled training. BACKGROUND: The failure of drivers to estimate headways correctly has been demonstrated in previous studies. METHODS: Two methods of training were used: time based (in seconds) and distance based (in a combination of meters and car lengths). For each method, learning curves were examined for 18 participants at speeds of 50, 80, and 100 km/hr. RESULTS: The results indicated that drivers were weak in estimating headway prior to training using both methods. The learning process was rapid for both methods and similar for all speeds; thus, after one trial with feedback, there was already a significant improvement. The learning was retained over time, for at least the 1 month examined in this study. CONCLUSION: Both the time and distance training of headway improved drivers' ability to attain required headways, with the learning being maintained over a retention interval. The learning process was based on perceptual cues from the driving scene and feedback from the experimenter, regardless of the formal training method. APPLICATION: The implications of these results are that all drivers should be trained in headway estimation using an objective distance measuring device, which can be installed on driver instruction vehicles.     

Headway feedback improves intervehicular distance: a field study

The effectiveness of a headway measuring and recording device was evaluated in terms of its ability to increase drivers' car-following distance. Forty-three drivers first drove for approximately 3 weeks without headway feedback and then for approximately 3 more weeks with immediate time headway (THW) feedback. Whenever the THW decreased to 1.2 s or less a red warning light came on, and whenever the THW decreased further to 0.8 s or less a buzzer was also sounded. The results showed that prior to receiving THW information,drivers drove at shorter headways than after they received that information. The effect of the feedback was to reduce the time spent in short headways (< or = 0.8 s) by approximately 25% (from 20% to 15% of the time) and to increase the time spent in safer longer headways (>1.2 s) by approximately 20% (from 57% to 65% of the time). The effect was similar for younger and older drivers, for male and female drivers, for urban and highway speeds, and for daytime and nighttime driving. An immediate application of these findings is to install headway feedback displays to drivers so that they may maintain safer headway distances than they do currently.     

Minimum and comfortable driving headways: reality versus perception

A field study was conducted to evaluate drivers' actual headways in car-following situations, their relationship to the drivers' brake reaction times, and their relationship to the drivers' ability to estimate those headways using different metrics. Drivers were asked to maintain "minimum safe distance" and "comfortable, normal distance with no intention to pass" behind the car ahead. The lead car speeds varied from 50 to 100 km/hr. The results showed that under both sets of instructions, drivers adjusted their distance headways in relation to speed, maintaining constant time headways. A significant portion of the drivers maintained time headways that are considered unsafe in relation to drivers' reaction times. There was no significant relationship between the minimal headways maintained by the drivers and their brake reaction times under conditions of maximum attention and preparedness to apply brakes. Accuracy of spoken estimates of headways varied widely among the three measures used to report perceived headway; meters and car lengths yielded much lower estimates (and ones closer to the actual headways) than did seconds. The results have implications for headway perception, driving safety, driver education, and smart cruise-control design.     

Effects of an in-vehicle collision avoidance warning system on short- and long-term driving performance

Many new in-vehicle systems focus on accident prevention by facilitating the driving task. One such driving aid is an in-vehicle collision avoidance warning system (IVCAWS), used to alert the driver to an impending collision. Our study evaluated the effects of an imperfect IVCAWS both on driver headway maintenance and on driver behavior in response to warning system errors. Our results showed that drivers tend to overestimate their headway and consequently drive with short and potentially dangerous headways, and that IVCAWSs are a useful tool for educating drivers to estimate headway more accurately. Moreover, our study showed that after a relatively short exposure to the system, drivers were able to maintain longer and safer headways for at least six months. The practical implications of these results are that the use of an IVCAWS should be considered for inclusion in driver education and training programs.     

An automatic real-time bus schedule redesign method based on bus arrival time prediction

Bus travel time often fluctuates greatly due to disturbance factors such as traffic conditions and passenger flow, which causes a reduction in the transit service as it cannot be provided as planned. Bus dispatching is necessary to handle this problem. Two crucial factors for real-time bus dispatching have been analysed in this study namely the bus arrival time prediction and timetable redesign. First, a bus arrival time prediction model combining Support Vector Regression (SVR) and Kalman Filter (K-SVR) was proposed. The headway is selected as an intermediate variable to improve the prediction accuracy by limiting the disturbance factors between two adjacent bus stops. Besides, by adjusting the parameters of the Kalman Filter, the predictive results are more suitable for practice to avoid the frequency of unnecessary timetable adjustment. Furthermore, an automatic timetable redesign method is given based on the proposed circle search algorithm, which can minimise the impact on the initial schedule by finding the minimum adjustment range in consideration of the normal working order. A case study in Shenzhen, China was conducted and the results verify that the K-SVR method could improve the prediction accuracy especially in peak hours. On this basis, in comparison with the traditional method, the timetable redesign algorithm could allocate the transit resources appropriately and perform well on indicators such as the headway fluctuation, compliance rate of headways, and schedule completeness. Moreover, it is more operable and valuable as a result of sending the departure instructions appropriately and maintaining the normal working order of drivers realistically.     

Why do drivers maintain short headways in fog? A driving-simulator study evaluating feeling of risk and lateral control during automated and manual car following

Drivers in fog tend to maintain short headways, but the reasons behind this phenomenon are not well understood. This study evaluated the effect of headway on lateral control and feeling of risk in both foggy and clear conditions. Twenty-seven participants completed four sessions in a driving simulator: clear automated (CA), clear manual (CM), fog automated (FA) and fog manual (FM). In CM and FM, the drivers used the steering wheel, throttle and brake pedals. In CA and FA, a controller regulated the distance to the lead car, and the driver only had to steer. Drivers indicated how much risk they felt on a touchscreen. Consistent with our hypothesis, feeling of risk and steering activity were elevated when the lead car was not visible. These results might explain why drivers adopt short headways in fog. Practitioner Summary: Fog poses a serious road safety hazard. Our driving-simulator study provides the first experimental evidence to explain the role of risk-feeling and lateral control in headway reduction. These results are valuable for devising effective driver assistance and support systems.     

Do drivers change their manual car-following behaviour after automated car-following?

There is evidence that drivers’ behaviour adapts after using different advanced driving assistance systems. For instance, drivers’ headway during car-following reduces after using adaptive cruise control. However, little is known about whether, and how, drivers’ behaviour will change if they experience automated car-following, and how this is affected by engagement in non-driving-related tasks (NDRT). The aim of this driving simulator study, conducted as part of the H2020 L3Pilot project, was to address this topic. We also investigated the effect of the presence of a lead vehicle during the resumption of control, on subsequent manual driving behaviour. Thirty-two participants were divided into two experimental groups. During automated car-following, one group was engaged in an NDRT (SAE Level 3), while the other group was free to look around the road environment (SAE Level 2). Both groups were exposed to Long (1.5 s) and Short (.5 s) Time Headway (THW) conditions during automated car-following, and resumed control both with and without a lead vehicle. All post-automation manual drives were compared to a Baseline Manual Drive, which was recorded at the start of the experiment. Drivers in both groups significantly reduced their time headway in all post-automation drives, compared to a Baseline Manual Drive. There was a greater reduction in THW after drivers resumed control in the presence of a lead vehicle, and also after they had experienced a shorter THW during automated car-following. However, whether drivers were in L2 or L3 did not appear to influence the change in mean THW. Subjective feedback suggests that drivers appeared not to be aware of the changes to their driving behaviour, but preferred longer THWs in automation. Our results suggest that automated driving systems should adopt longer THWs in car-following situations, since drivers’ behavioural adaptation may lead to adoption of unsafe headways after resumption of control.

     

Simulation of accident risk displays in motorway driving with traffic

The study used a vehicle-based driving simulator to evaluate two graphical displays, one showing risk probability in terms of safety margin (Time Headway, TH), and one showing risk severity in terms of Kinetic Energy (KE). Twentyseven subjects were randomly allocated to one of three experimental conditions: Control, TH, and KE. Subjects undertook three driving tasks (ABA design). For the second driving task in the TH and KE conditions, subjects drove in the presence of their respective feedback displays. Measures of TH and KE levels were taken, as well as subjective measures of risk and task loading. It was found that the KE display was more effective than the TH display in reducing the proportion of time subjects spent at short headways. The KE display was also effective in reducing the proportion of time subjects spent at high speed. The KE display appeared to affect the perception of risk (severity of potential accidents). It was concluded that further research evaluating displays that combined the positive effects of both parameters within a single representation display is needed.     

Imperfect in-vehicle collision avoidance warning systems can aid drivers

An experiment was conducted to determine the effects of an in-vehicle collision avoidance warning system (IVCAWS) on driver performance. A driving simulator was driven by 135 licensed drivers. Of these, 120 received alerts from the IVCAWS when their headway to a lead car was less than 2 s, and the other 15 (the control group) received no alerts. Drivers received varied alert interfaces: auditory, visual, and multimodal. The system had varied levels of reliability, determined by both false alarm rate and failure of the IVCAWS to alert to short headway. Results indicated that the IVCAWS led to safer (longer) headway maintenance. High false alarm rates induced drivers to slow down unnecessarily; large numbers of missed alerts did not have any significant impact on drivers. Driver acceptance of the system was mixed. Interface played a role in driver reliance on the system, with the multimodal interfaces generating least reliance. Actual or potential applications of this research include IVCAWS interface selection for greater system efficacy and user acceptance and the advisability of implementation, even of imperfect systems, for drivers who seek to maintain a safer headway.     

交通流多预期延迟模型与数值仿真

为了更准确地描述交通流,考虑驾驶员反应延迟时间和前车信息的非均衡使用,建立一种多预期延迟跟驰模型。线性稳定性分析表明,驾驶员反应延迟时间的增加会降低交通流的稳定性,多个前车信息的使用可以提高交通流的稳定性。数值仿真的结果表明,减少司机的反映延迟时间和适当地增加前车信息都能提高交通流的稳定性。为尽可能少地引入输入变量,不均衡地利用前车的车间距和速度差信息是必要的。理论和数值模拟的结果均表明驾驶员反应延迟在交通拥堵的形成过程中起着重要作用。     

The activation of eco-driving mental models: Can text messages prime drivers to use their existing knowledge and skills?

Eco-driving campaigns have traditionally assumed that drivers lack the necessary knowledge and skills and that this is something that needs rectifying. Therefore, many support systems have been designed to closely guide drivers and fine-tune their proficiency. However, research suggests that drivers already possess a substantial amount of the necessary knowledge and skills regarding eco-driving. In previous studies, participants used these effectively when they were explicitly asked to drive fuel-efficiently. In contrast, they used their safe driving skills when they were instructed to drive as they would normally. Hence, it is assumed that many drivers choose not to engage purposefully in eco-driving in their everyday lives. The aim of the current study was to investigate the effect of simple, periodic text messages (nine messages in 2 weeks) on drivers’ eco- and safe driving performance. It was hypothesised that provision of eco-driving primes and advice would encourage the activation of their eco-driving mental models and that comparable safety primes increase driving safety. For this purpose, a driving simulator experiment was conducted. All participants performed a pre-test drive and were then randomly divided into four groups, which received different interventions. For a period of 2 weeks, one group received text messages with eco-driving primes and another group received safety primes. A third group received advice messages on how to eco-drive. The fourth group were instructed by the experimenter to drive fuel-efficiently, immediately before driving, with no text message intervention. A post-test drive measured behavioural changes in scenarios deemed relevant to eco- and safe driving. The results suggest that the eco-driving prime and advice text messages did not have the desired effect. In comparison, asking drivers to drive fuel-efficiently led to eco-driving behaviours. These outcomes demonstrate the difficulty in changing ingrained habits. Future research is needed to strengthen such messages or activate existing knowledge and skills in other ways, so driver behaviour can be changed in cost-efficient ways.     

Visual strategies for the control of steering toward a goal

We have shown that people steer toward a target by aligning their heading with the target when target egocentric direction is not available for steering [24]. Here we examined what visual strategies people use to steer toward a target when target egocentric direction is available for steering. The display simulated a participant walking over a ground plane with a target placed off to one side. The participant’s simulated heading in the display was displaced 10° away from the participant’s straight ahead. A textured ground display that provided dense global optic flow and an empty ground display that provided nearly no flow were tested. Participants were instructed to use a joystick to control their simulated self-motion in the display to (a) steer toward the target, (b) center the target at their straight ahead, or (c) minimize the target drift on the screen. We found that participants produced similar heading error profiles when they were instructed to steer toward the target or to center the target straight ahead, but not when they were instructed to minimize the target movement on the screen. Furthermore, regardless of the instructions received, final heading errors were about 5° smaller with the textured than with the empty ground display, indicating the effect of optic flow on the control performance. We conclude that when target egocentric direction is available for steering, people do not steer toward the target by canceling its optical drift. Optic flow contributes to steering toward a target even when control could be based on egocentric direction alone.     

Distraction from multiple in-vehicle secondary tasks: vehicle performance and mental workload implications

This study investigates the impact of multiple in-vehicle information systems on the driver. It was undertaken using a high fidelity driving simulator. The participants experienced, paced and unpaced single tasks, multiple secondary tasks and an equal period of ‘normal’ driving. Results indicate that the interaction with secondary tasks led to significant compensatory speed reductions. Multiple secondary tasks were shown to have a detrimental affect on vehicle performance with significantly reduced headways and increased brake pressure being found. The drivers reported interaction with the multiple in-vehicle systems to significantly impose more subjective mental workload than either a single secondary task or ‘normal driving’. The implications of these findings and the need to integrate and manage complex in-vehicle information systems are discussed.     

The influence of performance standards and feedback on speed and accuracy in an electronically monitored data‐entry task

This study examined performance effects of using electronic performance monitoring (EPM) and feedback to induce compliance with speed and accuracy standards in a data entry task. The study focused on subjects who had difficulty meeting a preestablished data entry speed standard. Subjects performed a data‐entry task for 3 days. On the 1st (baseline) day, no performance standards were imposed, and all subjects were instructed to work at their normal speed and accuracy levels. For the 2nd and 3rd days of the experiment, subjects were assigned at random to one of two groups. In an experimental group, EPM and feedback were used to induce compliance with preestablished speed and accuracy standards. In a control group, subjects were unaware of EPM and received no feedback; they were instructed to continue working at their normal speed and accuracy levels. The introduction of EPM work management in the experimental group led to significant increases in data‐entry speed that were accompanied by significant increases in data‐entry errors. In addition, data‐entry errors produced by experimental subjects increased significantly over time during the workdays in which EPM work management was employed. These effects are discussed in terms of relevant research on goal setting and feedback utilization. The results suggest that when performance standards and feedback that emphasize speed more than accuracy are applied in EPM‐managed work settings, speed increments may be offset by decrements in work quality.     

Distraction from multiple in-vehicle secondary tasks: vehicle performance and mental workload implications

This study investigates the impact of multiple in-vehicle information systems on the driver. It was undertaken using a high fidelity driving simulator. The participants experienced, paced and unpaced single tasks, multiple secondary tasks and an equal period of 'normal' driving. Results indicate that the interaction with secondary tasks led to significant compensatory speed reductions. Multiple secondary tasks were shown to have a detrimental affect on vehicle performance with significantly reduced headways and increased brake pressure being found. The drivers reported interaction with the multiple in-vehicle systems to significantly impose more subjective mental workload than either a single secondary task or 'normal driving'. The implications of these findings and the need to integrate and manage complex in-vehicle information systems are discussed.     

The effects of using a portable music player on simulated driving performance and task-sharing strategies

This study examined the effects of performing scrollable music selection tasks using a portable music player (iPod Touch™) on simulated driving performance and task-sharing strategies, as evidenced through eye glance behaviour and secondary task performance. A total of 37 drivers (18–48 yrs) completed the PC-based MUARC Driver Distraction Test (DDT) while performing music selection tasks on an iPod Touch. Drivers’ eye glance behaviour was examined using faceLAB eye tracking equipment. Results revealed that performing music search tasks while driving increased the amount of time that drivers spent with their eyes off the roadway and decreased their ability to maintain a constant lane position and time headway from a lead vehicle. There was also evidence, however, that drivers attempted to regulate their behaviour when distracted by decreasing their speed and taking a large number of short glances towards the device. Overall, results suggest that performing music search tasks while driving is problematic and steps to prohibit this activity should be taken.     

How do argumentation diagrams compare when student pairs use them as a means for debate or as a tool for representing debate?

The objective of the research presented here was to study the influence of two types of instruction for using an argumentation diagram during pedagogical debates over the Internet. In particular, we studied how using an argumentation diagram as a medium of debate compared to using an argumentation diagram as a way of representing a debate. Two groups of students produced an individual argument diagram, then debated in pairs in one of the two conditions, and finally revised their individual diagrams in light of their debate. We developed an original analysis method (ADAM) to evaluate the differences between the argumentation diagrams constructed collaboratively during the interactions that constituted the experimental conditions, as well as those constructed individually before and after debate. The results suggest a complementary relationship between the usage of argumentation diagrams in the framework of conceptual learning. First, students who were instructed to use the argumentation diagram to represent their debate were less inclined to take a position in relation to the same graphical element while collaborating. On the other hand, students who were instructed to use the argumentation diagram alongside a chat expressed more personal opinions while collaborating. Second, the instructions given to the participants regarding the use of the argumentation diagram during the collaborative phase (either for debate or for representing a chat debate) have a significant impact on the post-individual graphs. In the individual graphs revised after the collaborative phase, participants who used the graph to represent their debate added more examples, consequences and causes. It follows that a specific usage for an argumentation diagram can be chosen and instructions given based on pedagogical objectives for a given learning situation.     

A Review of:“The Remembering Self: Construction and Accuracy in the Self-narrative”, edited by ULRIC NEISSER and ROBYN FIVUSH,Cambridge University Press,New York (1994), pp. x + 301, £30.00, ISBN 0-521-43194-8

Driving is a task that requires the timely detection of critical events and relevant changes in traffic circumstances. Adaptation of speed and safety margins allows drivers to control the time available to react to potential hazards. One of the basic safety margins in driving is the time headway preserved with respect to cars ahead. To avoid rear-end collisions, drivers have to detect decelerations of lead cars. It can be assumed that fast or abrupt decelerations of the lead car are detected faster than slow or gradual decelerations. Moreover, expected decelerations are presumably detected faster than unexpected decelerations. Drivers' responses to rather abrupt and more gradual decelerations of the lead were investigated in a driving simulator. Situational traffic cues were used to manipulate the driver's expectations. Drivers adjusted the timing of their responses very well to the level of deceleration of the lead car. If cues in the environment indicated that the lead car was likely to decelerate, drivers reacted faster. Moreover, drivers increased their headway before the lead car actually started to decelerate, which can be considered an anticipatory response. In general, anticipation allows drivers to maintain their preferred headway and control time pressure in driving.     

An empirical investigation of a dynamic brake light concept for reduction of rear-end collisions through manipulation of optical looming

The concept of dynamically manipulating the optical looming cues of a lead vehicle's brake lights is investigated as a means of potentially reducing the frequency of rear-end collisions in automobile driving. In a low-fidelity driving simulator, 40 participants were instructed to follow a leading vehicle (LV) and appropriately respond to braking of the LV, under three visibility conditions: day, night-time with following vehicle (FV) headlights, and night-time without FV headlights. During some LV braking events, separation and size of the brake lights of the LV were expanded or contracted, by a nominally imperceptible amount, to simulate an effective virtual time shift in the headway of the LV. Results show that this manipulation was most effective for very poor visibility conditions: at night with no headlights, for which LV brake lights were most salient. When confronting a LV with expanding or contracting brake lights, subjects generally braked sooner or later respectively, in comparison with the no manipulation case. The concept shows some promise for causing drivers to brake sooner in emergencies.     

基于编队技术的地铁列车运行控制研究

首先分析了移动闭塞条件下地铁列车的运行规律,建立了地铁列车的动力学模型,研究移动闭塞条件下地铁列车车组间的控制,采用基于事件的控制理论和编队技术降低列车间的最小追踪允许间隔,在保证不撞车以及尽量减少站外停车的前提下,提高地铁线路的通过能力,并且能够方便地实现系统的重新配置以及各子系统间的协调协作。以相邻的三列列车运行为例,研究在移动闭塞条件下后续列车的控制策略,根据列车的走行距离以及前后列车间所要求保留的安全距离,动态调整列车的运行速度、加速度。