Safety implications of co-locating road signs: A driving simulator investigation

BackgroundAs road complexity increases the requirement for number of road signs also increases, although the amount of road side space does not. One practical strategy to address this is to present multiple road signs on the same gantry (sign co-location). However, there is very little research on the safety implications of this practice.Method36 participants (mean age = 42.25 years, SD = 13.99, 18 females) completed three driving simulator scenarios, each scenario had a different sign co-location condition: no co-location, dual co-location and triple co-location. Each scenario presented similar information using direction signs, variable message signs and variable speed limit signs, under. Each drive included standard motorway driving (100 km/h speed zone) in free flow traffic and one emergency event where a lead vehicle suddenly braked. The scenario order was counterbalanced and the emergency event vehicle varied.ResultsOverall, there was no impact of co-locating signs on general driving performance. No significant difference was observed between conditions for reaction time and minimum headway in response to the emergency event. Participants were able to correctly choose their destination whether the signs were co-located or not.DiscussionFor the particular configuration of signs tested there is no evidence that co-location negatively impacts driving performance. However, there may be some implications for travel speed and the manner in which the emergency event is responded to. Future work should confirm the findings on real roads. These findings provided support for sign co-location as a practical and safe option for displaying multiple road signs in a confined area.     

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.     

The estimation of vehicle speed and stopping distance by pedestrians crossing streets in a naturalistic traffic environment

The ability to estimate vehicle speed and stopping distance accurately is important for pedestrians to make safe road crossing decisions. In this study, a field experiment in a naturalistic traffic environment was conducted to measure pedestrians’ estimation of vehicle speed and stopping distance when they are crossing streets. Forty-four participants (18–45 years old) reported their estimation on 1043 vehicles, and the corresponding actual vehicle speed and stopping distance were recorded. In the speed estimation task, pedestrians’ performances change in different actual speed levels and different weather conditions. In sunny conditions, pedestrians tended to underestimate actual vehicle speeds that were higher than 40 km/h but were able to accurately estimate speeds that were lower than 40 km/h. In rainy conditions, pedestrians tended to underestimate actual vehicle speeds that were higher than 45 km/h but were able to accurately estimate speeds ranging from 35 km/h to 45 km/h. In stopping distance estimation task, the accurate estimation interval ranged from 60 km/h to 65 km/h, and pedestrians generally underestimated the stopping distance when vehicles were travelling over 65 km/h. The results show that pedestrians have accurate estimation intervals that vary by weather conditions. When the speed of the oncoming vehicle exceeded the upper bound of the accurate interval, pedestrians were more likely to underestimate the vehicle speed, increasing their risk of incorrectly deciding to cross when it is not safe to do so.     

On-road study investigating the mode of feedback delivery on young drivers’ speed management

Feedback has been shown to be instrumental in learning. Refining how it is delivered in driver training has the potential to reduce crash risk. Therefore, the aim of the present study was to examine the effect of the medium in which feedback is delivered (verbal, written, graphical) on young drivers’ speed management behaviour. Sixty young drivers, randomly allocated to one of four feedback groups (i.e., Control, Verbal feedback, Written feedback, and Graphical feedback) completed one training and two test drives using an instrumented vehicle on-road. After the first (baseline) drive, participants were provided feedback about the number of times they exceeded the speed limit, their maximum speed, as well as the financial penalties associated with such driving behaviour, and safety implications. The content of feedback remained the same for all training groups, except for the manner in which the feedback was presented. Verbal feedback was provided verbally by the researcher; written feedback on paper; and graphical feedback using a series of graphs on a computer screen. Control received no such intervention. Two test drives followed, one immediate post-training, and the second one week post-training. Feedback, irrespective of medium improved young drivers’ speed management. Verbal and graphical feedback yielded the greatest reduction in speeding behaviour, with graphical feedback having the most impact in the two speed zones under examination (50 km/h & 80 km/h). Control showed the poorest speed management behaviour in all drives. These findings have important implications for the development of a new approach to improve young drivers’ speed management behaviour.     

Exploration of older drivers’ speeding behaviour

Speeding increases crash risk and resulting injury severity. Older drivers are at increased risk of injury due to frailty, at increased risk of crashing due to slower reaction times, and have less agility judging time and distance compared to younger drivers. However, there is little objective evidence about older drivers’ speeding behaviour. Cross-sectional data from older drivers living in the suburban outskirts of Sydney, Australia, were used to determine the proportion of drivers involved in speed events, and examine factors that may influence this behaviour. Driving speed was estimated in approximately one-second intervals using Global Positioning System (GPS) location. Speed events were defined as driving 1 km/h or more, with 3% tolerance, above a single speed limit, averaged over 30-s of travel. Driving data from one-week were recorded for 344 participants aged 75–94 years (median 80). The majority of participants (78%) were involved in a speed event. Speed events per participant ranged from zero to 186 (median 8). Younger participants, those living in rural areas, and those driving on familiar roads closer to home were more likely to be involved in speed events adjusted for distance driven. In addition, rural residents were more likely to be involved in speed events when they had not been a driver involved in a crash during the previous year compared to those involved in a crash. Measures of visual and cognitive function did not predict involvement with speed events per distance (p > 0.2). These findings are important for policy-makers and researchers addressing older drivers’ speeding to reduce the incidence of crashes and resulting fatalities and injuries. As no evidence was found for speeding being associated with functional decline, countermeasures to address speeding for other drivers seem likely to be relevant to older drivers.     

Bicyclists’ speed adaptation strategies when conducting self-paced vs. system-paced smartphone tasks in traffic

The increasing prevalence of mobile phone usage while cycling has raised concerns, even though the number of cyclists involved in accidents does not increase at a comparable rate. A reason for this may be how cyclists adapt travelling speed and task execution to the current traffic situation. The aim of this study is to investigate speed adaptation among cyclists when conducting self-paced (initiated by the cyclist) vs. system-paced (initiated by somebody else) smartphone tasks in real traffic.Twenty-two cyclists completed a track in real traffic while listening to music, receiving and making calls, receiving and sending text messages, and searching for information on the internet. The route and the types of tasks were controlled, but the cyclists could choose rather freely when and where along the route to carry out the tasks, thus providing semi-naturalistic data on compensatory behaviour.The results clearly show that cyclists use conscious strategies to adapt their speed to accommodate the execution of secondary phone tasks. Regarding tactical behaviour, it was found that cyclists kept on cycling in 80% of the system-paced cases and in 70% of the self-paced cases. In the remaining cases, the cyclists chose to execute the phone task while standing still or when walking. Compared to the baseline (17.6 ± 3.5 km/h), the mean speed was slightly increased when the cyclists listened to music (18.2 ± 3.7 km/h) and clearly decreased when they interacted with the phone (13.0 ± 5.0 km/h). The speed reduction profile differed between self-paced and system-paced tasks with a preparatory speed reduction before task initiation for self-paced tasks.In conclusion, when the cyclists had the chance they either stopped or adapted their speed proactively to accommodate the execution of the phone task. For self-paced tasks, the speed reduction was finalised before task initialisation, and for system-paced tasks the speed adaptation occurred in reaction to the incoming task. It is recommended to investigate whether the observed compensatory behaviour is enough to offset the possible negative effects of smartphone use.     

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.     

Treadmill based reference running data for healthy subjects is dependent on speed and morphological parameters

ObjectiveTo obtain spatiotemporal and dynamic running parameters of healthy participants and to identify relationships between running parameters, speed, and physical characteristics.MethodA dynamometric treadmill was used to collect running data among 417 asymptomatic subjects during speeds ranging from 10 to 24 km/h. Spatiotemporal and dynamic running parameters were calculated and measured.ResultsResults of the analyses showed that assessing running parameters is dependent on running speed. Body height correlated with stride length (r = 0.5), cadence (r = −0.5) and plantar forefoot force (r = 0.6). Body mass also had a strong relationship to plantar forefoot forces at 14 and 24 km/h and plantar midfoot forces at 14 and 24 km/h.ConclusionThis reference data base can be used in the kinematic and kinetic evaluation of running under a wide range of speeds.     

Effects of reduced threshold of automated speed enforcement on speed and safety

This study was designed to evaluate the effects of a reduced threshold of the fixed automated speed enforcement system on speed and safety on a two-lane rural road. The threshold was lowered from 20 km/h to 4 km/h and the public was informed about the change. Driving speeds on the experimental and control road before and after the change were compared. The main results showed that the reduced threshold decreased the mean speed by 2.5 km/h, the standard deviation of speed by 1.1 km/h and the proportion of exceeding vehicles by 11.8 percentage units. In conclusion, lowering the threshold of automated speed enforcement combined with an appropriate information campaign bring about a significant speed reduction that could contribute to substantial safety benefits.     

Transcultural validation and reliability of the Spanish version of the behaviour of young novice drivers scale (BYNDS) in a Colombian young driver population

The overrepresentation of young drivers in road crashes, and the fatalities and injuries arising from those crashes, is an intractable problem around the world. A plethora of research has led to the development and application of a range of research tools, including self-report survey instruments. One such instrument, the five-factor Behaviour of Young Novice Driver Scale (BYNDS), was developed in an Australian young driver population, and has recently been validated in a New Zealand young driver population. The current study aimed to validate the BYNDS in a Colombian young driver population, the first application of the instrument in a developing country. Translation from English to Spanish, and back translation from Spanish to English, in addition to culturally-appropriate modifications (such as changing ‘right hand side’ to ‘left hand side’) resulted in a Spanish version of the BYNDS (BYNDS-Sp). The BYNDS-Sp was administered to a sample of 392 young drivers aged 16–24 years (n = 353 aged 19–24 years) with a valid driver’s licence. An exploratory factor analysis revealed a six factor structure using 40 of the original 44 BYNDS-Sp items, accounting for 58.5% of the variance in self-reported risky driving behaviour. Ninety-three percent of participants reported having ready access to their own vehicle (42% owned their own vehicle), with Colombian young drivers most likely to report driving at night and on the weekend. The majority of participants reported driving in excess of posted speed limits (e.g., only one third of participants reported never driving 10–20 km/h over the speed limit), and driving in response to their mood (e.g., only one third of participants reported they never drove faster if in a bad mood). As such, the BYNDS-Sp can reveal patterns of problematic behaviours (such as risky driving exposure), in addition to specific behaviours of concern (such as carrying passengers at night, and driving when tired), guiding the development and implementation of interventions targeting the risky driving behaviour of young drivers in Colombia. In addition, the BYNDS-Sp can be used as a measure of intervention success if used as a baseline and as a follow-up tool. Further research can investigate the utility and applicability of the BYNDS-Sp in other Spanish-speaking countries, such as Spain and Mexico.     

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.     

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.     

A validation study of driving errors using a driving simulator

BackgroundDriving simulators have become an important research tool in road safety. They provide a safer environment to test driving performance and have the capacity to manipulate and control situations that are not possible on-road.AimTo validate a laboratory-based driving simulator in measuring on-road driving performance by type and mean driving errors.MethodsParticipants were instructed to drive a selected route on-road. The same route was programmed in the driving simulator using the UC/Win-road software. All participants completed a background questionnaire. On-road driving behaviours of participants and driving behaviours in the simulator were assessed by an occupational therapist and two trained researchers using an assessment form. Interclass correlations were calculated to assess the inter-rater agreement between the researchers on driving behaviours. Paired t-tests were used to assess differences in driving performance between the simulator and on-road assessments.ResultsA convenience sample of 47 drivers aged 18–69 years who held a current Western Australian class C licence (passenger vehicle) were recruited into the study. The mean age was 34.80 years (SD: 13.21) with twenty-six males (55.32%) and 21 females (44.68%) completing the study. There was no statistical difference between the on-road assessment and the driving simulator for mirror checking, left, right and forward observations, speed at intersections, maintaining speed, obeying traffic lights and stop signs.ConclusionThe preliminary results provide early support for the relative validity of the driving simulator which may be used for a variety of road safety outcomes with reduced risk of harm to participants.     

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.     

Analysis of rainfall impacts on platooned vehicle spacing and speed

This paper investigates the impact of rainfall on the behavior of drivers in a car-following state by analyzing the differences in time gap, speed, and following distance of platooned vehicles between no-rain and rainy weather conditions on a two-lane rural state highway. Time gap, following distance, and individual vehicle speed were observed. Platooned vehicles were identified by a maximum time gap threshold of 4 s, allowing for interactions between vehicles beyond perception–reaction time. Rainfall intensity was utilized as the measure of local precipitation conditions and was categorized according to American Meteorological Society standards. The analysis showed that rainy weather conditions were strongly correlated with greater spread in speed distributions when compared to dry conditions. Further, the shift from no-rain to rain showed an increase in time gap and a reduction in speed. No statistically significant differences were observed between following distances in any weather conditions – suggesting that drivers tend to maintain following distance irrespective of weather conditions and speed reduction causes the observed time gap increase. This is supported by the observed 5.6% decrease in mean time gap – from 1.97 s to 2.1 s and the 3.7% decrease in mean speed – from 47 mph (75.6 km/h) to 45.3 mph (72.9 km/h).     

The effect of yellow light onset time on older and younger drivers’ perception response time (PRT) and intersection behavior

To understand why older drivers are over-represented in intersection crashes, this study sought to describe the intersection performance of older and younger drivers when traffic lights changed from green to yellow at the last second. Using a moderate-fidelity driving simulator, time to stop line (TSL) at yellow onset was manipulated as drivers approached intersections at 70 km/h (42 mph). Seventy-seven participants, approximately balanced for gender and age group, volunteered from the age categories of 18 to 24, 25 to 35, 55 to 64, and 65+. Driver decisions to stop or go were predicted using a logistic regression model with time to stop line as the single significant predictor. There were no age differences in perception response time (PRT). Older drivers approached intersections at a lower velocity and stopped more accurately than younger drivers. For those drivers who chose to go through the yellow light, speed profiles across the intersection and intersection clearance indicate that older drivers are more likely to be in the intersection when the light changed to red. A PRT of 1.0 s for yellow signal phasing was sufficient for all age groups.     

Exploring the influences of country-level factors on mature-aged women’s drink driving attitudes

The current study examined drink driving attitudes among mature-aged women in Sweden and Australia, two countries with a Blood Alcohol Concentration (BAC) limit of 0.02% and 0.05%, respectively. The study aimed to identify attitudes that might influence drink driving tendency among this group of women and further show how these attitudes vary across countries. Using an ethnographic approach, 15 mature-aged women (Sweden: mean age = 52.5 years, SD = 4.8; Australia: mean age 52.2 years, SD = 3.4) were interviewed in each country. General patterns and themes from the data were developed using thematic analysis methods. The findings indicate that while women in both countries viewed drink driving negatively, the understanding of what the concept entailed differed between the two samples. The Swedish women appeared to cognitively separate alcohol consumption and driving, and consequently, drink driving was often spoken of as driving after any alcohol consumption. The Australian women’s understanding of drink driving was more closely related to the legal BAC limit. However, for some Australian women, a “Grey Zone” existed, which denoted driving with a BAC of just above the enforceable limit. While illegal, these instances were subjectively seen as similar to driving with a BAC of just under the legal limit and therefore not morally reprehensible. The practice of cognitively separating drinking from driving appeared to have implications for the tendency to drink and drive among the interviewed women. These findings are discussed in relation to current policy and legislation in Australia and the need for further research into mature-aged women’s drink driving is outlined.     

Reliability of forward head posture evaluation while sitting,standing, walking and running

Forward head posture has been evaluated mostly by visual observation or simple non-invasive measurements without a standardized evaluation method or protocol. In this experimental study, the reliability of existing forward head-posture measurement methods was evaluated by computing the intra-class correlation coefficients of three different head-position variables (two horizontal gap variables and one head-orientation variable) in seven different posture conditions from 20 asymptomatic participants. The position variables of the head were measured three times using a three-dimensional motion capture system while sitting comfortably, sitting with the back straight, standing comfortably, standing with the back straight, walking at 4 and 6 km/h on a treadmill, and running at 8 km/h on a treadmill. Intra-class correlation coefficients between repetitive measures ranged from 0.81 to 0.96, and high correlation coefficient values (>0.9) were produced when the head-position variables were measured during straight sitting, straight standing, and walking at 6 km/h. Among the three head-position variables, a horizontal gap between the tragus and the 7th cervical vertebra was recorded more consistently than other variables. Results of this study highlight the importance of a standardized evaluation protocol for more reliable assessment of the forward head posture.     

Controllability of Partially Automated Driving functions – Does it matter whether drivers are allowed to take their hands off the steering wheel?

Different motor vehicle manufacturers have recently introduced assistance systems that are capable of both longitudinal and lateral vehicle control, while the driver still has to be able to take over the vehicle control at all times (so-called Partial Automation). While these systems usually allow hands-free driving only for short time periods (e.g., 10 s), there has been little research whether allowing longer time periods of hands-off driving actually has a negative impact on driving safety in situations that the automation cannot handle alone. Altogether, two partially automated assistance systems, differing in the permitted hands-off intervals (Hands-off system vs. Hands-on system, n = 20 participants per assistance condition, age 25–70 years) were implemented in the driving simulation with a realistic take-over concept. The Hands-off system is defined by having a permitted hands-off interval of 120 s, while the Hands-on system is defined by a permitted hands-off interval of 10 s. Drivers’ reactions at a functional system limit were tested under conditions of high ecological validity: while driving in a traffic jam, participants unexpectedly encountered a time-critical situation, consisting of a vehicle at standstill that appeared suddenly and required immediate action. A visual-auditory take-over request was issued to the drivers. Regardless of the hands-off interval, all participants brought the vehicle to a safe stop. In spite of a stronger brake reaction with the Hands-on system, no significant differences between assistance levels were found in brake reaction times and the criticality of the situation. The reason for this may be that most of the drivers kept contact with the steering wheel, even in the Hands-off condition. Neither age nor prior experience with ACC was found to impact the results. The study thus demonstrates that permitting longer periods of hands-off driving does not necessarily lead to performance deficits of the driver in the case of take-over situations, if a comprehensive take-over concept is implemented.