Merging into heavy motorway traffic by young and elderly drivers

An increase in the number of Heavy Goods Vehicles on motorways may lead to additional problems in the interaction with an increased number of elderly drivers. Elderly drivers suffer from reduced information processing speed and capacity, and in general effectively compensate for this by taking more time. However, this strategy, regulating task demands by slowing down will make merging into motorway traffic actually more difficult.In an experiment performed in a driving simulator, young and elderly drivers merged into motorway traffic. Driver behaviour and mental workload were studied while the following factors were manipulated: type of traffic and density of Heavy Goods Vehicles on the main road, the length of the acceleration lane, presence of a slowly driving lead car, and presence of a driver support system that encouraged the drivers to speed up if their speed was too low.Results show that the effects of an increased number of Heavy Goods Vehicles on the main road were not more adverse for elderly than for the young participants, with the exception that elderly drivers merged at a lower speed. This lower speed could make the manoeuvre more risky in real traffic. The support system and an extended acceleration lane facilitated merging, while a slowly driving lead car impeded completion of the manoeuvre.     

Age and inconsistency in driving performance

Research in cognitive neuropsychology suggests that investigation of the within-person variability, or inconsistency, of cognitive performance may provide valuable insights into ageing mental processes. It is rare though, for this interest in intraindividual variability to extend to everyday activities. As this may provide important information about driving behaviour, we therefore assessed age differences in driving inconsistency in younger (n = 24, M age = 21.29 years) and older (n = 21, M age = 71.24 years) persons who drove in residential, urban and motorway conditions in a fully immersive driving simulator. In measures of headway (maintaining a safe distance to a preceding vehicle) and lateral lane position, older drivers exhibited significantly greater performance inconsistency, and this was particularly marked in the faster motorway condition. Older drivers also recorded greater perceived mental demands associated with driving, and greater within-person variability across a range of cognitive measures. The findings suggest that age-related deficits in attentional and executive control may affect the consistency of driving performance in older persons. Discussion considers interventions to introduce in-vehicle systems to help maintain attention in older drivers, and to intervene when safety-critical boundaries are exceeded.     

Effects of work zone configurations and traffic density on performance variables and subjective workload

This paper investigates the effect of changing work zone configurations and traffic density on performance variables and subjective workload. Data regarding travel time, average speed, maximum percent braking force and location of lane changes were collected by using a full size driving simulator. The NASA-TLX was used to measure self-reported workload ratings during the driving task. Conventional lane merge (CLM) and joint lane merge (JLM) were modeled in a driving simulator, and thirty participants (seven female and 23 male), navigated through the two configurations with two levels of traffic density. The mean maximum braking forces was 34% lower in the JLM configuration, and drivers going through the JLM configuration remained in the closed lane longer. However, no significant differences in speed were found between the two merge configurations. The analysis of self-reported workload ratings show that participants reported 15.3% lower total workload when driving through the JLM. In conclusion, the implemented changes in the JLM make it a more favorable merge configuration in both high and low traffic densities in terms of optimizing traffic flow by increasing the time and distance cars use both lanes, and in terms of improving safety due to lower braking forces and lower reported workload.     

Using mobile telephones: cognitive workload and attention resource allocation

Driver distraction is recognized as being one of the central causes of road traffic incidents and mobile telephones are tangible devices (among many other electronic devices) that can distract the driver through changes in workload. Forty participants completed a motorway route characterized by a low level of road complexity in the form of vehicle handling and information processing. A peripheral detection task (PDT) was employed to gauge mental workload. We compared effects of conversation type (simple versus complex) and telephone mode (hands-free versus handheld) to baseline conditions. The participants' reaction times increased significantly when conversing but no benefit of hands-free units over handheld units on rural roads/motorways were found. Thus, in regard to mobile telephones, the content of the conversation was far more important for driving and driver distraction than the type of telephone when driving on a motorway or similar type of road. The more difficult and complex the conversation, the greater the possible negative effect on driver distraction.     

Effects of steering demand on lane keeping behaviour, self-reports, and physiology. A simulator study

In this study a driving simulator was used to determine changes in mental effort in response to manipulations of steering demand. Changes in mental effort were assessed by using subjective effort ratings, physiology, and the standard deviation of the lateral position. Steering demand was increased by exposure to narrow lane widths and high density oncoming traffic while speed was fixed in all conditions to prevent a compensatory reaction. Results indicated that both steering demand factors influence mental effort expenditure and using multiple measures contributes to effort assessment. Application of these outcomes for adaptive automation is envisaged.     

A comparison of different ways to approximate time-to-line crossing (TLC) during car driving

Three experiments are presented in which the accuracy of different methods to approximate time-to-line crossing is assessed the first experiment TLC was computed, using a trigonometric method, during normal driving while the vehicle stayed in lane. The minima of TLC were compared with two approximations and it was found computing TLC as lateral distance divided by lateral velocity gave poor results. It was concluded that this simple approximation is not suitable for measuring TLC minima in studies of driver behaviour. A way of computing TLC that takes account of the curved path of the vehicle resulted in a good fit of TLC minima. In two other experiments the vehicle exceeded the lane boundary, either intentionally as a result of a lane change manoeuvre, or unintentionally as a result of impaired driving. In these cases no TLC minima exists since these only occur as a result of correcting steering actions to stay within the lane. In contrast to normal lane keeping, it was found that prior to crossing the lane boundary, the simple approximation resulted in more accurate estimation of available time before the lane boundary is exceeded compared to the more complex approximation. This indicates that for lane keeping support systems and systems that detect when the driver has fallen asleep and drifts out of lane, a simple algorithm for TLC estimation may give reliable results, while this algorithm is not accurate enough for more fundamental studies of driver behaviour. However, the reliability of the approximation is only satisfactory over a very short time range before the lane boundary is actual exceeded. This may result in warnings that come too late and result in too little time to respond for the driver.     

Driving performance impairments due to hypovigilance on monotonous roads

Drivers' ability to react to unpredictable events deteriorates when exposed to highly predictable and uneventful driving tasks. Highway design reduces the driving task mainly to a lane-keeping manoeuvre. Such a task is monotonous, providing little stimulation and this contributes to crashes due to inattention. Research has shown that driver's hypovigilance can be assessed with EEG measurements and that driving performance is impaired during prolonged monotonous driving tasks. This paper aims to show that two dimensions of monotony - namely road design and road side variability - decrease vigilance and impair driving performance. This is the first study correlating hypovigilance and driver performance in varied monotonous conditions, particularly on a short time scale (a few seconds). We induced vigilance decrement as assessed with an EEG during a monotonous driving simulator experiment. Road monotony was varied through both road design and road side variability. The driver's decrease in vigilance occurred due to both road design and road scenery monotony and almost independently of the driver's sensation seeking level. Such impairment was also correlated to observable measurements from the driver, the car and the environment. During periods of hypovigilance, the driving performance impairment affected lane positioning, time to lane crossing, blink frequency, heart rate variability and non-specific electrodermal response rates. This work lays the foundation for the development of an in-vehicle device preventing hypovigilance crashes on monotonous roads.     

Driving performance impairments due to hypovigilance on monotonous roads

Drivers’ ability to react to unpredictable events deteriorates when exposed to highly predictable and uneventful driving tasks. Highway design reduces the driving task mainly to a lane-keeping manoeuvre. Such a task is monotonous, providing little stimulation and this contributes to crashes due to inattention. Research has shown that driver’s hypovigilance can be assessed with EEG measurements and that driving performance is impaired during prolonged monotonous driving tasks. This paper aims to show that two dimensions of monotony – namely road design and road side variability – decrease vigilance and impair driving performance. This is the first study correlating hypovigilance and driver performance in varied monotonous conditions, particularly on a short time scale (a few seconds). We induced vigilance decrement as assessed with an EEG during a monotonous driving simulator experiment. Road monotony was varied through both road design and road side variability. The driver’s decrease in vigilance occurred due to both road design and road scenery monotony and almost independently of the driver’s sensation seeking level. Such impairment was also correlated to observable measurements from the driver, the car and the environment. During periods of hypovigilance, the driving performance impairment affected lane positioning, time to lane crossing, blink frequency, heart rate variability and non-specific electrodermal response rates. This work lays the foundation for the development of an in-vehicle device preventing hypovigilance crashes on monotonous roads.     

The effects of visibility conditions,traffic density,and navigational challenge on speed compensation and driving performance in older adults

Research on how older drivers react to natural challenges in the driving environment is relevant for both the research on mental workload and that on age-related compensation. Older adults (M age = 70.8 years) were tested in a driving simulator to assess the impact of three driving challenges: a visibility challenge (clear day, fog), a traffic density challenge (low density, high density) and a navigational challenge (participants followed the road to arrive at their destination, participants had to use signs and landmarks). The three challenge manipulations induced different compensatory speed adjustments. This complicated interpretation of the other measures of driving performance. As a result, speed adjustment indices were calculated for each condition and participant and composite measures of performance were created to correct for speed compensation. (These speed adjustment indices correlated with vision test scores and subscales of the Useful Field of View^®.) When the composite measures of driving performance were analyzed, visibility × density × navigational challenge interactions emerged for hazard RT and SD of lane position. Effects were synergistic: the impact of the interaction of challenge variables was greater than the sum of independent effects. The directions of the effects varied depending on the performance measure in question though. For hazard RT, the combined effects of high-density traffic and navigational challenge were more deleterious in good visibility conditions than in fog. For or SD of lane position, the opposite pattern emerged: combined effects of high-density traffic and navigational challenge were more deleterious in fog than in clear weather. This suggests different aspects of driving performance tap different resources.     

雾对基于可见光的车辆定位性能的研究

分析雾环境下利用LED交通灯进行车辆定位的性能,讨论了接收角度、道路宽度、雾环境下接收端信噪比等对车辆定位范围的影响。仿真结果表明:信号最佳接收角度为25°;车辆距离LED交通灯20 m之内时,道路宽度对信号的接收功率影响较大;在靠近交通灯处,车辆位于第二车道上的定位距离比车辆位于第一车道的定位距离少2.2 m;晚间接收端的信噪比优于白天,晚间的定位范围大于白天;与晴朗天气相比,雾天信噪比下降较大,将极大影响车辆的可定位范围,因此为保证安全驾驶,车辆在雾天行驶过程中需要更多的制动时间。     

The influence of cruise control and adaptive cruise control on driving behaviour--a driving simulator study

Although Cruise Control (CC) is available for most cars, no studies have been found which examine how this automation system influences driving behaviour. However, a relatively large number of studies have examined Adaptive Cruise Control (ACC) which compared to CC includes also a distance control. Besides positive effects with regard to a better compliance to speed limits, there are also indications of smaller distances to lead vehicles and slower responses in situations that require immediate braking. Similar effects can be expected for CC as this system takes over longitudinal control as well. To test this hypothesis, a simulator study was conducted at the German Aerospace Center (DLR). Twenty-two participants drove different routes (highway and motorway) under three different conditions (assisted by ACC, CC and manual driving without any system). Different driving scenarios were examined including a secondary task condition. On the one hand, both systems lead to lower maximum velocities and less speed limit violations. There was no indication that drivers shift more of their attention towards secondary tasks when driving with CC or ACC. However, there were delayed driver reactions in critical situations, e.g., in a narrow curve or a fog bank. These results give rise to some caution regarding the safety effects of these systems, especially if in the future their range of functionality (e.g., ACC Stop-and-Go) is further increased.     

基于演化博弈论的可变导向车道设置策略研究

可变导向车道的设置，在提高道路通行效率的同时会造成驾驶人情绪紧张或者因不了解路况导致违规甚至发生事故，对交通系统的安全和稳定运行产生负面影响。以交管部门设置可变导向车道的策略选择为研究目标，结合驾驶人走可变导向车道时产生的紧张情绪损失等因素，构建交管部门−驾驶人群体两方博弈模型。采用演化博弈论的方法分析博弈双方选择行为演化和稳定策略，对系统中存在的5个演化均衡点进行分析，得到系统的3种理想稳定状态和相对应的参数条件，为交管部门设置可变导向车道进行策略选择提供理论支撑。     

Inter-vehicle mobile ad hoc network for road transport systems

Access to information services while on the move is becoming increasingly prevalent within transport systems. Whereas Internet access is now common place in trains, it still remains a challenge for vehicles, particularly when travelling through high speed motorways. Motorway vehicles equipped with wireless communication nodes form an ad hoc network have been examined by which data can be exchanged among them without the need for a pre-installed infrastructure. The main challenge with such an infrastructure-less network is developing communications and protocols that can deliver robust and reliable ad hoc communications between vehicles, when the relative speed between vehicles that can be extremely high under opposite traffic conditions. To address this opposite direction effect, a solution has been presented by minimising the effect of opposite traffic on routing packets. Firstly, a router direction index is introduced to enhance the performance of ad hoc on demand distance vector protocol in updating its routing table and secondly, a new queue priority mechanism is proposed which is based on cross-layer collaboration. Simulations were performed for an ad hoc network consisting of 200 vehicles driving with speeds between 90 and 120 km/h on a two-way motorway for different traffic loads sent through a Gateway adjacent to the motorway. The results obtained demonstrate a performance increase in the average data goodput and less routing overhead for the proposed solution     

Monitoring drivers’ mental workload in driving simulators using physiological measures

Many traffic accidents are caused by, or at least related to, inadequate mental workload, when it is either too low (vigilance) or too high (stress). Creating variations in mental workload and accident-prone driving for research purposes is difficult in the real world. In driving simulators the measurement of driver mental workload is relatively easily conducted by means of physiological measures, although good research skills are required and it is time-consuming. The fact that modern driving simulator environments are laboratory-equivalent nowadays allows full control with respect to environmental conditions, scenarios and stimuli, and enables physiological measurement of parameters of mental workload such as heart rate and brain activity. Several examples are presented to illustrate the potential of modern high-standard driving simulator environments regarding the monitoring of drivers’ mental workload during task performance.     

The effects of mobile telephoning on driving performance

The effects of telephoning while driving were studied in three different traffic conditions, i.e. in light traffic on a quiet motorway, in heavy traffic on a four-lane ring-road, and in city traffic. Twelve subjects, unfamiliar with mobile telephones, drove an instrumented vehicle for one hour each day during three weeks and while in each of the three traffic conditions, had to operate the mobile telephone for a short while. To ensure a fixed "heavy traffic load" in the second condition, the subjects were instructed to follow another instrumented vehicle (at a safe distance). The results showed a significant effect of telephoning while driving as opposed to normal driving (i.e., not involving telephone conversation), on the effort subjectively measured by an effort scale and objectively measured by heartrate indices and on some of the measured parameters of driving performance. One half of the subjects had to operate the telephone manually, the other half performed the telephone task with a handsfree mobile telephone set. The subjects who operated the handsfree telephone showed better control over the test vehicle than the subjects who operated the handheld telephone, as measured by the steering wheel movements. Also, a clear improvement over time in the course of the 15 test days was found for some of the measurements. As a consequence of the results, some advice concerning mobile telephoning can be given to authorities, manufacturers, and users.     

Traveller information service based on real-time toll data in Austria

The aim of this work is to demonstrate the suitability of existing toll collection data from the highranking road network in Austria for the generation of traffic information. The development of an area-wide, high-quality traffic information service in various implementations as prototypes was target of the project Smart Mobility Analysis of Real-time Toll-data (GO-SMART). In order to achieve feasible travel time estimations detection and rejection of distorting data is essential. Several methods of outlier detection and filtering have been tested and compared. An algorithm exhibiting good attributes with regard to effectiveness, feasibility and performance has been designed and applied to the data. The developed method is adapted to the specific behaviour and features of the available data that are, among others, caused by system conditions of the tolling system. The proposed method is a combination of moving average, z-score and plausibility checks. For the purpose of displaying fast and up-to-date traffic information a weighted aggregation is suggested. Weights depend on timeliness and related vehicle type of single observations. In order to allow jam detection, a similar behaviour of observed vehicles (chargeable heavy good vehicles) and passenger cars is required in congested situations. This is necessary to assure the same behaviour of the measured part of the traffic (heavy good vehicles) and of the overall traffic. The required assumption could be reproduced for single velocity values as well as for approximation of density?velocity relations. Prototypes of pre-trip and ontrip traveller information services are presented.     

A simulator study of the effects of singing on driving performance

This study aimed to investigate how singing while driving affects driver performance. Twenty-one participants completed three trials of a simulated drive concurrently while performing a peripheral detection task (PDT); each trial was conducted either without music, with participants listening to music, or with participants singing along to music. It was hypothesised that driving performance and PDT response times would be impaired, and that driver subjective workload ratings would be higher, when participants were singing to music compared to when there was no music or when participants were listening to music. As expected, singing while driving was rated as more mentally demanding, and resulted in slower and more variable speeds, than driving without music. Listening to music was associated with the slowest speeds overall, and fewer lane excursions than the no music condition. Interestingly, both music conditions were associated with slower speed-adjusted PDT response times and significantly less deviation within the lane than was driving without music. Collectively, results suggest that singing while driving alters driving performance and impairs hazard perception while at the same time increasing subjective mental workload. However, singing while driving does not appear to affect driving performance more than simply listening to music. Further, drivers’ efforts to compensate for the increased mental workload associated with singing and listening to music by slowing down appear to be insufficient, as evidenced by relative increases in PDT response times in these two conditions compared to baseline.     

Evaluation of rear-end crash risk at work zone using work zone traffic data

This paper aims to evaluate the rear-end crash risk at work zone activity area and merging area, as well as analyze the impacts of contributing factors by using work zone traffic data. Here, the rear-end crash risk is referred to as the probability that a vehicle is involved in a rear-end crash accident. The deceleration rate to avoid the crash (DRAC) is used in measuring rear-end crash risk. Based on work zone traffic data in Singapore, three rear-end crash risk models are developed to examine the relationship between rear-end crash risk at activity area and its contributing factors. The fourth rear-end crash risk model is developed to examine the effects of merging behavior on crash risk at merging area. The ANOVA results show that the rear-end crash risk at work zone activity area is statistically different from lane positions. Model results indicate that rear-end crash risk at work zone activity area increases with heavy vehicle percentage and lane traffic flow rate. An interesting finding is that the lane closer to work zone is strongly associated with higher rear-end crash risk. A truck has much higher probability involving in a rear-end accident than a car. Further, the expressway work zone activity area is found to have much larger crash risk than arterial work zone activity area. The merging choice has the dominated effect on risk reduction, suggesting that encouraging vehicles to merge early may be the most effective method to reduce rear-end crash risk at work zone merging area.     

Impact of distracted driving on safety and traffic flow

Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16–25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner that impacts safety and traffic flow negatively when distracted.     

Relationship between crash rate and hourly traffic flow on interurban motorways

This paper describes the relationship between crash incidence rates and hourly traffic volume and discusses the influence of traffic on crash severity, based on observations made on 2000 km of French interurban motorways over 2 years. Incidence rates involving property damage-only crashes and injury-crashes are highest when traffic is lightest (under 400 vehicles/h). These incidence rates are at their lowest when traffic flows at a rate of 1000-1500 vehicles/h. For heavier traffic flows, crash incidence rates increase steadily as traffic increases on 2- and 3-lane motorways and inflect on 2-lane motorways when traffic increases to a level of 3000 vehicles/h. For an equivalent light traffic level, the number of crashes is higher on three-lane than on 2-lane motorways and higher at weekends (when truck traffic is restricted) than on weekdays. In heavy traffic, the number of crashes is higher on weekdays. We found no significant difference between the number of daytime and night-time crashes, whatever the traffic. No difference was observed in crash severity by number of lanes or period in the week for a given level of traffic. However, severity is greater at night and when hourly traffic is light. Compared to the number of vehicles on the road, light traffic is a safety problem in terms of frequency and severity, and road safety campaigns targeting motorway users to influence their behavior in these driving conditions should be introduced.