The role of edge lines in curve driving

In order to evaluate the role of edge lines in curve driving we examined steering behaviour in the face of unexpected gradual changes in road geometry. Experienced drivers (N = 13) operating a fixed-base driving simulator steered a car along a single-lane (3.80 m or 7.60 m wide) winding road. The experimental track consisted of eight 90° curves with radii of curvature varying between 75 m and 500 m, separated by 500-m long straight line segments. The model-based nature of the simulator was used to create unexpected online changes in road geometry, implemented through a gradual displacement of one or both edge lines while drivers steered around the delineated bend. Although they regulated their speed as a function of road curvature, drivers were found to consistently cut into and out of the curves. When the edge lines did not move, drivers stabilized their lane position during the 20°–70° curve segments, adopting a position closer to the interior edge line for the narrower lane width and smaller radii of curvature. Motion of the interior edge line, whether inward or outward, gave rise to systematic changes in lane position, while motion of the exterior edge line did not affect driving behaviour. Overall, the results point to a visuo-motor strategy of steering based on zeroing-out changes in the rate of change of angular bearing of the tangent point.     

Manual drivers’ experience and driving behavior in repeated interactions with automated Level 3 vehicles in mixed traffic on the highway

In the near future, conditionally automated vehicles (CAVs; SAE Level 3) will travel alongside manual drivers (≤ SAE level 2) in mixed traffic on the highway. It is yet unclear how manual drivers will react to these vehicles beyond first contact when they interact repeatedly with multiple CAVs on longer highway sections or even during entire highway trips. In a driving simulator study, we investigated the subjective experience and behavioral reactions of N = 51 manual drivers aged 22 to 74 years (M = 41.5 years, SD = 18.1, 22 female) to driving in mixed traffic in repeated interactions with first-generation Level 3 vehicles on four highway sections (each 35 km long), each of which included three typical speed limits (80 km/h, 100 km/h, 130 km/h) on German highways. Moreover, the highway sections differed regarding the penetration rate of CAVs in mixed traffic (within-subjects factor; 0%, 25%, 50%, 75%). The drivers were assigned to one of three experimental groups, in which the CAVs differed regarding their external marking, (1) status eHMI, (2) no eHMI, and (3) a control group without information about the mixed traffic. After each highway section, drivers rated perceived safety, comfort, and perceived efficiency. Drivers were also asked to estimate the penetration rate of CAVs on the previous highway section. In addition, we analyzed drivers’ average speed and their minimum time headways to lead vehicles for each speed zone (80 km/h, 100 km/h, 130 km/h) as well as the percentage of safety critical interactions with lead vehicles (< 1 s time headway). Results showed that manual drivers experienced driving in mixed traffic, on average, as more uncomfortable, less safe and less efficient than driving in manual traffic, but not as dangerous. A status eHMI helps manual drivers identify CAVs in mixed traffic, but the eHMI had no effect on manual drivers’ subjective ratings or driving behavior. Starting at a level of 25% Level 3 vehicles in mixed traffic, participants' average speed decreased significantly. At the same time, the percentage of safety critical interactions with lead vehicles increased with an increasing penetration rate of CAVs. Accordingly, additional measures may be necessary in order to at least keep the existing safety level of driving on the highway.     

Behavioural adaptation or constraint? The effect of curve proximity on driving behaviour

Horizontal curves are typically associated with increased crash risk when compared with straight roads, but recent analyses have suggested that having more frequent sharp curves decreases the relative crash risk posed by each curve. Here, 90 drivers completed a simulated rural drive with either high proximity (160 m straight tangent between curves) or low proximity (1200 m tangent) curves. Curve proximity had a significant effect on approach speeds, with drivers in the high proximity curve drive showing significantly lower mean and maximum approach speeds before entering the curve. However, they also showed an unexpected tendency to higher speeds while negotiating the curve itself. The current study provides direct empirical evidence that driving behaviour on approach to a given curve is significantly affected by the proximity of other curves, and therefore highlights the need to factor in the characteristics of the road on approach to the curve, as well as the features of the curve itself when assessing risk.     

Pro-social behaviour in young passengers: Predictive utility of the social reaction pathway of the prototype willingness model

This study examined the social reaction pathway of the Prototype Willingness Model (PWM) to assess how attitudes, subjective norms, prototype perception (favourability and similarity), and risk perception influenced young passengers’ willingness to speak up to a driver exceeding the posted speed limit by either 5 km/h or 10 km/h. It was hypothesised that participants would be more willing to speak up to drivers’ travelling 10 km/h over the posted speed limit than 5 km/h over the posted speed limit. Further, it was hypothesised that the PWM constructs would significantly predict passenger willingness to speak up to a driver travelling 5 km/h over the posted speed limit and 10 km/h over the posted speed limit. Young Australians aged 17 to 25 years (N = 136, Mage = 19.32, 77.9% female) were recruited to complete a 30-minute online questionnaire. As predicted, passengers were significantly more willing to speak up to drivers travelling at 10 km/h over the posted speed limit than drivers travelling 5 km/h over the posted speed limit. Further, the results from a linear regression revealed that some of the PWM constructs were effective in explaining the variance in willingness to speak-up to drivers travelling either 5 km/h or 10 km/h over the posted speed limit. These findings address a gap in road safety research by shifting focus from the behaviour of drivers to the behaviour of passengers. The focus on the pro-social behaviour of speaking up to drivers performing risk taking behaviours may help to inform future educational campaigns and interventions designed to reduce young peoples’ involvement in road crashes.     

The effectiveness of “Soft-blocking” for reducing clicking on-screen while driving

Smartphone usage while driving is recognized as a compromise on road safety. We investigated if silencing and hiding of notifications from drivers (soft blocking) can reduce clicks on the screen while driving and if the effect of the soft blocking would be different for different speed thresholds (STs) (i.e., at driving speed greater than 0 km/h, greater than 1 km/h….and greater than 90 km/h). Drivers installed a smartphone application, which continuously monitored their phones. In the intervention group (N = 22), the application switched to the soft blocking mode during the study's intervention period, while in the control group (N = 29) it remained in a recording-only mode. We ran a Poisson regression model on the click events frequency (CEF) to estimate the soft blocking effect for each of the STs between 0 and 90 km/h. Our analyses indicated that the soft blocking effectiveness was indeed speed-dependent and pointed to a decline in CEF from ST > 55 km/h and to mixed results if ST < 55 km/h. We identify a potential of soft blocking to reduce phone usage while driving and recommend ST-dependent soft blocking. We also recommend using different STs in future investigations on the effectiveness of soft blocking.     

Dynamic traffic management on a familiar road: Failing to detect changes in variable speed limits

Variable speed limits (VSL) are used more commonly around the globe lately. Although on a macroscopic level positive effects of VSLs have been reported, the caveat is that the impact of VSLs is very sensitive to the level of driver compliance. Thus far it is unknown whether all individual drivers are actually able to notice when a speed limit changes into another speed limit; a prerequisite for purposeful speed limit compliance in the first place. To simulate regular driving conditions, twenty-four participants were familiarised with a particular route by driving the same route in a driving simulator nineteen times on five separate days. Part of the route consisted of a motorway where VSL signs were regularly displayed above every driving lane. At drive nineteen, speed limits changed from 80 km/h to 100 km/h on four out of eight consecutive signs. After passing all signs, one expects 6.25% of the participants still to be unaware that the speed limit had increased (based on chance), while the results showed most participants had failed to notice the speed limit change (58.3%). Instead, they saw what they expected to see: a speed limit of 80 km/h. If the speed change had been vice versa, in other words from 100 km/h to 80 km/h, this would immediately result in speed offences, though not deliberately at all.     

When norms turn perverse: Contextual irrationality vs. rational traffic violations

A perfectly adequate traffic rule can turn “perverse” in situations when it does little to enhance road safety but seems – at least in the drivers’ minds – directed primarily at punishing those who violate it. This study examined traffic rule obedience in situations in which the rule was not in accordance with real safety needs. Six rules with major impact on road safety were analyzed: waiting at red traffic lights, legal overtaking, obeying the 50 km/h speed limit, wearing seatbelts, legal stopping/parking, and driving the car in good technical condition. Participants evaluated how adequate these rules are for safety. Then they were faced with six scenarios, that made each of these rules appear irrational, and were asked to report their potential engagement in deviant behavior. The survey data were collected in a sample of 605 drivers. Multiple regression analyses showed that in most situations rule violation depended on the usual deviant behavior, perceived irrationality of the rule, little respect for the law and low risk perception. These factors best explained the 50 km/h speed limit violation. The results suggest that the lack of situational risk factors, which makes the rule look meaningless, is important determinant of rule violation. Implications for massive disobedience and road safety are discussed.     

A naturalistic study of the impact of message framing on highway speeding

Speeding is the most common road violation, and is one of the main causes of crashes. To protect road users, authorities use sanctions and preventive measures to prompt drivers to observe speed limits. However, the efficacy of prevention messages varies according to a number of factors, among which risk framing is important. We ran a study to test whether gain is more effective than loss (framing effect). Four anti-speeding messages were presented on variable-message signs, along one side of a busy 8-lane highway in France (speed limit: 130 km/h – 80 mph), during 6 weekends. Within a between subject design, the messages differed in orientation (gain vs. loss vs. no message) and theme (crash vs. fuel consumption). The drivers’ speed was recorded on the highway 2 km (1.25 miles) after the sign (6486 recordings of speed). The results showed that speed was lower when a message was displayed than in the control condition, and when the message was gain-framed rather than loss-framed. These effects were stronger on the left lanes (overtaking lanes). Hence, gain framed messages are recommended for prevention campaigns at least when no risk factor is salient.     

Speed reductions and judgments of travel time loss: Biases and debiasing

Priority decisions concerning maintenance or reconstruction of roads are made with the aim of road improvements with as little traffic disturbance and time loss as possible. However, it cannot be avoided that speed will be reduced and travel time increased during the time of construction. The present study shows how intuitive judgments of travel time losses are biased in a way similar to the times saving bias (Svenson, 2008), but not perfectly corresponding to that bias. This means that when speed is decreased from a slow speed <50 km/h, the time loss is underestimated and when speed is decreased from a high speed >80 km/h it is overestimated. Also, drivers, politicians and policy makers who do not make exact calculations are likely victims of the time loss bias. The time loss bias was weakened but not eliminated by a debiasing instruction including mathematical computations of travel times. When driving speed restrictions are implemented, in particular on fast motorways, it is necessary to consider and counteract the time loss bias and inform the public. This can be done, for example, in communications about travel time facts, by information in driver training and by mounting temporary road signs informing about the average travel time prolongation due to a road work.     

A comparison of experienced and novice drivers’ rear-end collision avoidance maneuvers under urgent decelerating events

A leading vehicle’s sudden deceleration can lead to a rear-end collision. Due to a lack of driving experience, novice drivers have a greater tendency to be involved in these accidents. Most previous studies have examined driver response time and braking behaviors, but few researchers have focused on what experienced and novice drivers did after their feet touched the braking pedal and their hands turned the steering wheel. These braking and steering parameters are essential in understanding driver avoidance behavior during emergencies. We programmed rear-end crash risk scenarios to examine experienced and novice drivers’ behaviors thoroughly using a driving simulator. Twenty experienced and twenty five novice subjects participated in our experiments, and their braking and steering maneuvers were recorded when leading vehicles ran at 60 km/h, 80 km/h and 100 km/h. The results showed that the two groups of subjects tended to execute two kinds of maneuvers to avoid crashes: braking only (novice 33%, experienced 19%) and the combination of braking with steering (novice 22%, experienced 26%). When the novice drivers executed braking with steering, their response time and steering duration were significantly longer than those of the experienced drivers who executed braking with steering. As the speed increased, the novice drivers’ response time, maximum braking force and maximum steering angle were significantly affected. These results showed that novice drivers should brake only when the leading vehicle suddenly decelerates. The experienced drivers executed steadier maneuvers. Their risk perception time was shorter, and their maximum braking force and the maximum steering angles were smaller. The response time, braking intensity and steering wheel angle should be considered when developing rear-end collision warning systems.     

Diverging diamond interchanges: A driving simulator study

This study assessed driver performance while navigating a Diverging Diamond Interchange (DDI) compared to a standard intersection in a driving simulator. A total of 201 Western Australian (WA) drivers aged 18–80 years completed the simulator drive and questionnaire. Measures of driving simulator performance assessed included time spent out of lane, number of lane excursions, compliance to the speed limit, crashes and near misses. Other driving measures, which were recorded by the researcher, included driver errors/violations such as red-light violations, wrong way violations and navigation errors. Qualitative information was also obtained in a post exit interview with each participant regarding the difficulties they experienced when driving through the DDI. A repeated-measure analysis of variance (r-ANOVA) was undertaken to examine differences in intersection type (DDI versus standard intersection) and driving performance measures from the driving simulator. The only significant result was compliance to the speed limit (F (1, 656) = 160.11, p < 0.001) on the driving simulator. A higher proportion of red-light violations were observed by the researcher as participants navigated through the DDI, compared to the standard intersection. Qualitative comments from participants also highlighted the need for better signage and road markings. Recommendations when DDIs are implemented include community education on speed limit compliance, avoidance of red-light violations and design improvements regarding signage and road markings.     

Timing of early warning stages in a multi stage collision warning system: Drivers’ evaluation depending on situational influences

By means of car2x communication technologies (car2x) driver warnings can be presented to drivers quite early. However, due to their early timing they could be misunderstood by drivers, distract or even disturb them. These problems arise if, at the moment of the warning, the safety–critical situation is not yet perceivable or critical. In order to examine, when drivers want to receive early warnings as a function of the situation criticality, a driving simulator study was conducted using the two early warning stages of a multi stage collision warning system (first stage: informing the driver; second stage: prewarning the driver). The optimum timing to activate these two early warning stages was derived by examining the drivers’ evaluation of these timings concerning their appropriateness and usefulness. As situational variation, drivers traveling at about 100 km/h were confronted with slow moving traffic either driving at 25 km/h or 50 km/h at the end of a rural road.In total, 24 participants were tested in a within-subjects design (12 female, 12 male; M = 26.6 years, SD = 7.2 years). For both stages, drivers preferred an earlier timing when approaching slow moving traffic traveling at 25 km/h (first stage: 447 m, second stage: 249 m ahead of the lead vehicle) compared to 50 km/h (first stage: 338 m, second stage: 186 m ahead of the lead vehicle). The drivers’ usefulness rating also varied with the timing, spanning a range of 8 s for driver-accepted timing variations and showed correspondence to the drivers’ appropriateness ratings. Based on these results and those of a previous study, a timing function for each of the two early warning stages depending on the speed difference between the safety–critical object and the host vehicle is presented. Indirectly, similar adaptations are already implemented in current collision warning systems, which use the time-to-collision to give drivers acute warnings in a later stage, when an immediate reaction of the driver may still prevent a collision. However, this study showed that drivers also favor this kind of adaptation for earlier warning stages (information and prewarning). Thus, adapting the timing according to the drivers’ preferences will contribute to a better acceptance of these collision warning systems.     

How to nudge drivers to reduce speed: The case of the left-digit effect

To decrease the negative consequences of a road crash, even a small reduction in driving speeds can make a significant difference. We examined the possible application of the left-digit effect as a nudge to reduce road speed. In the marketing field, this effect is based on reporting price tags that are characterized by a low leftmost number and a high rightmost number (e.g., a price tag of €14.99 rather than €15.00). We applied the same strategy to improve road safety. Participants were college students (43.75% female, mean age = 24.06 years in Study 1; 50% female, mean age = 23.53 years in Study 2) who were asked to drive in a simulator on a route that had both usual unmodified road signs (e.g., 50 km/h) and the same road signs increased or decreased by one unit (e.g., 49, 51 km/h). We compared the average median speeds in road segments with unmodified road signs with those in road segments with the corresponding modified signs. The average median speeds in the presence of a sign modified by the reduction of 1 km/h were significantly lower compared with the median average speeds recorded with unmodified signs. We showed that the application of psychological insights can reduce driving speeds and therefore increase road safety.     

Understanding and modelling risky driving behaviour on high-speed corridors

This study explores the relationships among various factors influencing risky driving behaviours, particularly on high-speed corridors (expressways). A total of 546 samples are collected from licenced drivers through an online survey. Exploratory factor analysis confirms the four-factor solution and the same is verified using confirmatory factor analysis. These factors are individual aberrant driving behaviour (violations and errors), risky driving behaviour performed by surrounding vehicles and dangerous manoeuvres due to prevailing road environment. Structural equation modelling is used to establish the relationships amongst the aforementioned factors. The results of the study describe that observed risky driving behaviour on expressways is mostly affected by drivers’ individual aberrant driving (γ = 0.62) followed by risky driving behaviour performed by surrounding vehicles (γ = 0.39) and least affected by the road environment (γ = 0.36). The individual driving behaviour is mostly affected by violations (γ = 0.47) followed by errors (γ = 0.38). Furthermore, differences in Driving Behaviour Questionnaire (DBQ) scales are analysed with respect to the demographic variables. Results suggest that male and young drivers report more violations than female and older drivers, respectively, however, female drivers are more error prone than male drivers. The findings of the study can be useful to identify the potential road safety countermeasures to improve the driving style as well as the driving environment.     

The role of drivers’ social interactions in their driving behavior: Empirical evidence and implications for car-following and traffic flow

Models for describing the microscopic driving behavior rarely consider the “social effects” on drivers’ driving decisions. However, social effect can be generated due to interactions with surrounding vehicles and affect drivers’ driving behavior, e.g., the interactions result in imitating the behavior of peer drivers. Therefore, social environment and peer influence can impact the drivers’ instantaneous behavior and shift the individuals’ driving state. This study aims to explore empirical evidence for existence of a social effect, i.e., when a fast-moving vehicle passes a subject vehicle, does the driver mimic the behavior of passing vehicle? High-resolution Basic Safety Message data set (N = 151,380,578) from the Safety Pilot Model Deployment program in Ann Arbor, Michigan, is used to explore the issue. The data relates to positions, speeds, and accelerations of 63 host vehicles traveling in connected vehicles with detailed information on surrounding environment at a frequency of 10 Hz. Rigorous random parameter logit models are estimated to capture the heterogeneity among the observations and to explore if the correlates of social effect can vary both positively and negatively. Results show that subject drivers do mimic the behavior of passing vehicles –in 16 percent of passing events (N = 18,099 total passings occurred in freeways), subject vehicle drivers are observed to follow the passing vehicles accelerating. We found that only 1.2 percent of drivers normally sped up (10 km/hr in 10 s) during their trips, when they were not passed by other vehicles. However, if passed by a high speed vehicle the percentage of drivers who sped up is 16.0 percent. The speed change of at least 10 km/hr within 10 s duration is considered as accelerating threshold. Furthermore, the acceleration of subject vehicle is more likely if the speed of subject driver is higher and more surrounding vehicles are present. Interestingly, if the difference with passing vehicle speed is high, the likelihood of subject driver’s acceleration is lower, consistent with expectation that if such differences are too high, the subject driver may be minimally affected. The study provides new evidence that drivers’ social interactions can change traffic flow and implications of the study results are discussed.     

Investigating the effectiveness of perceptual treatments on a crest vertical curve: A driving simulator study

Rural roads are characterized by a high percentage of run-off-the-road accidents and head-on collisions, mainly caused by inappropriate speeds and failure to maintain a proper lateral position along the roadway alignment. Among several road safety treatments, low-cost perceptual measures are considered an effective tool, as they generally increase the risk perceived by drivers, or even alter the drivers’ speed perception, and consequently tempting them to decrease their speeds. Their effectiveness has been widely recognized in a number of studies, especially with respect to road intersections and curves.The overall aim of this study is to investigate the effects of different perceptual treatments on driving speed, along a crest vertical curve of an existing two-lane rural road, in order to identify the most effective measure to reduce speed and define its subsequent implementation in the field. Three perceptual treatments were tested using a driving simulator: white peripheral transverse bars, red peripheral transverse bars and optical speed bars, with each one being painted along the approaching tangent to the crest vertical curve. The effects of these speed-reducing measures were investigated using a sample of forty-four participants, by comparing the driving speeds with those recorded under a baseline condition (without a treatment); these were also used to validate the driving simulator’s speed measurements with those found in the field. Moreover, subjective measures were collected, consisting of the driver’s static evaluation of the desired speed, risk perception and markings comprehension, based on screen shot pictures that represented the simulated configurations of the treatments.The findings demonstrated an overall effectiveness of the perceptual treatments, although only the red peripheral transverse bars were found to significantly reduce the driving speeds (−6 km/h). The analysis of the questionnaire yielded interesting information and demonstrated the importance of performing driving simulation tests for evaluating the effectiveness of perceptual treatments.Finally, the results confirmed the enormous potential of using driving simulators to pinpoint a number of speed-reducing measures, and consequently select the most effective one that reduces cost and promotes safety before its actual implementation in the field.     

The impact of daytime running (LED) lights on motorcycles speed estimation: A driving simulator study

Motorcycles are the most common type of vehicle involved in traffic deaths, especially in underdeveloped and developing countries. In order to prevent traffic accidents involving motorcyclists, one of the measures is to respect the “see and be seen” rule. If a motorcycle is perceived in time or another motorcyclist is spotted in time, there is enough time to react, in order to avoid a traffic accident or reduce the consequences. In many countries, it is for this reason that the use of daytime running lights on motor vehicles and/or motorcycles is legally prescribed. In the Republic of Serbia, a country that belongs among the least developed countries, about a third of those killed in traffic accidents are motorcycle drivers. For these reasons, an experimental study was conducted on a driving simulator to examine the importance of (non) use of daytime running lights on the estimation of motorcycle speed. Three different situations were examined: without daytime running lights, with daytime running lights, and with LED daytime running lights; for test speeds of 30 km/h, 50 km/h, 70 km/h, and 90 km/h. In the experiment, 128 young drivers participated. The results showed that the speed of a motorcycle with LED daytime running lights on is perceived most accurately.     

The influence of music genres on the driving behaviour of young drivers and their visual scanning of the environment

Recently, distractions have been recognized as a significant risk factor in road traffic. This simulator study aims to investigate how different music genres affect the driving behaviour of young drivers and their visual scanning of the environment in urban settings. The genres considered were Croatian pop, foreign pop, classical music, metal, and Balkan folk music, while on one road section there was no music. The research sample consisted of 61 participants (44 males and 17 females) with a mean age of 24.58 years and a mean driving experience of 5.25 years. The influence of music on the drivers’ behaviour was analysed on the basis of the data collected from the driving simulator, eye tracking glasses, and structured observation during driving sessions. It was found that the highest average speed (around 60 km/h) was recorded while the participants were listening to Balkan folk and metal music, while other music genres, as well as the “no music” condition, influenced driving speed in a similar way to one another and the participants drove at 50 km/h on average. Furthermore, the results suggest that the music genre also affects how drivers visually scan the environment (the number of gazes classified as fixations and number of road signs looked at). The findings obtained may be used in road safety work and practical recommendations and further research are discussed.     

Do internals speed less and externals speed more to cope with the death anxiety?

Past research has showed that mortality salience (MS) increases reckless driving and speeding when the individual perceives driving to be relevant to his or her self-esteem. We claimed that drivers’ control orientations also play a significant role in the relationship between MS and speeding. We hypothesized that both a general desirability of control and traffic locus of control (T-LOC) would moderate the effect of MS on speeding. We tested our hypothesis using an online experiment on a sample of 208 young male drivers. Participants were exposed to either mortality or dental pain salience, and they filled out desirability of control, T-LOC, and self-report speeding measures. The results showed that, for individuals with low desirability of control, MS increased preferred speed and decreased intention to comply with speed limit and the percentage of time complied with the speed limit on urban roads with 50 km/h speed limit. For individuals with high desirability of control, on the other hand, MS increased intention to comply with the speed limit on rural roads and percentage of the time complied with the speed limit on both urban and rural roads. In contrast, the interaction between MS and T-LOC showed that an external T-LOC is positively associated with both intention to comply and the percentage of the time complied with the speed limits only on rural roads with 90 km/h.