The effect of speed limit credibility on drivers' speed choice

Credibility of speed limits is a key factor affecting drivers’ compliance with speed limits. Two experiments were conducted to investigate how credibility of speed limits affects judgments of appropriate speed. The first experiment aimed to establish speeds deemed appropriate by investigating Malaysians drivers’ judgments of the appropriate speed to drive based on photographs of roads with the speed limit sign erased. Drivers chose speeds which correlated with but were higher than the actual speed limits of the roads. Analysis of road characteristics suggested they based their decisions mainly on features of the road itself rather than of the roadside. The second experiment tested the impact of credibility of speed limit information on the speed drivers judged appropriate. Drivers judged the appropriate speed to drive for the same photographs as in Experiment 1 with speed limit information provided. Four conditions were included: two conditions where the speed limit posted was 10% higher or 10% lower than the appropriate speed established in Experiment 1 (credible speed limits), and two conditions where the posted speed limit was 50% higher or 50% lower than the appropriate speed (non-credible speed limits). Posted speed limits did affect drivers’ judgments about the appropriate speed to drive. Credibility also influenced judgments whereby drivers selected appropriate speeds consistent with the speed limits for the 10% lower condition, but not for speed limits that deviated highly from the appropriate speed judged in Experiment 1.     

Effects of position of speed limit signs and the presence of speed camera on Malaysian drivers’ speed choice: An eye-tracking study

Speeding is one of the most common driving violations in the world including in Malaysia. Reducing speed-related fatalities is one of Malaysia’s strategies to improve road safety. The current study aimed to investigate the effect of speed limit sign positioning and the presence of speed camera on drivers’ judgments about the appropriate speed to drive and their associated eye movements. Twenty participants took part in the study, and thirty two images of roads with a range of actual speed limits were presented. In each picture the displayed speed limit was edited to 30% lower than what participants think is appropriate on average. Speed limit signs were either presented on the road or on the speed limit sign boards at the road sides, and a speed camera sign was either present or not. Drivers judged a lower appropriate speed to drive when the camera sign was present than absent, while there was a wider spread of differences between judged and displayed speed when the speed limit sign was presented on the board than on the road. Drivers were quicker in fixating and looked more at the general area in which the speed limit sign appeared. Therefore drivers’ visual attention across scenes may be manipulated by the sign positions. These low-cost interventions could be useful in managing speed choice in Malaysia.     

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.     

Speed choice in relation to speed limit and influences from other drivers

Speeding is a general problem in traffic and exploring factors underlying the choice of speed is an important task. In the present paper, based on data from Swedish drivers on 90 km/h roads, drivers’ attitudes towards speeding and influences from other road users on the drivers’ speed choice were investigated. Unobtrusively recorded vehicle speeds were compared with drivers’ responses to questions concerning their speed choice (N=533). The present investigation replicates a previous study on 50 km/h roads, where a model including measures of attitudes and perceptions about others’ behaviour could explain about 15% of observed behaviour. In the present study, where a majority of the drivers observed exceeded the speed limit, a similar model could explain 41% of the variance in observed speed. Theoretical and practical implications of the results are discussed.     

Reading the situation: The relationship between dyslexia and situational awareness for road sign information

Road signs are tools that provide crucial information to drivers about various roadway situations. Therefore, the present study aimed to assess the levels of ‘situation awareness’ held by drivers in relation to these signs. This study also assessed the relationship between dyslexia, road sign comprehension, and road sign situation awareness, thus building on the limited research in this area. Drivers completed measures of road sign comprehension and dyslexia. Drivers then completed three drives on a driving simulator; each followed by a probe containing queries about the perception, comprehension and projection of road signs seen in the preceding drive. Situation awareness was lowest at the level of projection. Further, dyslexia was negatively associated with road sign comprehension, and road sign situation awareness, suggesting that the disorder may be detrimental for multiple forms of road sign processing. Implications are provided in the form of a ‘SAFE’ driver training program that targets a holistic form of road sign processing which takes into account sign meanings in relation to both in-vehicle and outer-vehicle factors; thus encouraging proactive driver behaviour.     

The role of preference in speed choice

Individual differences with regard to speed preference may be a source of speed heterogeneity and conflicts in traffic, such as tailgating and dangerous overtaking. The main aim of the current study was to explore drivers’ speed preferences when driving for different reasons (saving money on fuel, driving safely, driving for fun or driving as usual) and the relationship of these preferences to observed speeds and self-reported speed. 193 drivers were interviewed at five different locations, and were asked about their speeds on roads they had just travelled. Drivers’ speeds on these roads were also sampled with a speed gun. The results showed large differences between speeds chosen for different driving purposes; the lowest speeds were chosen when the goal was economy and the highest when driving for fun. In addition, there were individual differences in speed preferences such that some drivers indicated that their usual speed was above what they believed was a safe speed while others indicated that they usually drove even slower than what they thought was safe. These differences may account for much of the speed heterogeneity observed in on-road behaviour. The results also showed that drivers’ speed choices are highly influenced by their usual speeds, even more so than their beliefs regarding what constitutes a safe speed, which may help explain non-compliance with speed limits. No relationship was found between speed choice and risk perception.     

Stability in drivers' speed choice

Repeated speed measurements were obtained to examine drivers' consistency in speed choice. Drivers were observed at two locations along a route or for two days at the same location. Single carriageway roads were used with posted speed limits of 70 and 90 km/h. Correlation coefficients between repeated speed measures ranged from .49 to .81 for free-flowing vehicles. Higher consistency between measures was found where segments of the road were homogenous. Consistency in relation to speed limit varied as a function of roads and direction of travel. From 4% to 41% of the drivers observed legal speeds at both sites and between 43% and 100% travelled over the speed limits at both sites. The results are discussed in terms of using self-reported speed in driver surveys and modelling of driver behaviour.     

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.     

A comparison of self-nominated and actual speeds in work zones

Despite significant research on drivers’ speeding behavior in work zones, little is known about how well drivers’ judgments of appropriate speeds match their actual speeds and what factors influence their judgments. This study aims to fill these two important gaps in the literature by comparing observed speeds in two work zones with drivers’ self-nominated speeds for the same work zones. In an online survey, drivers nominated speeds for the two work zones based on photographs in which the actual posted speed limits were not revealed. A simultaneous equation modeling approach was employed to examine the effects of driver characteristics on their self-nominated speeds. The results showed that survey participants nominated lower speeds (corresponding to higher compliance rates) than those which were observed. Higher speeds were nominated by males than females, young and middle aged drivers than older drivers, and drivers with truck driving experience than those who drive only cars. Larger differences between nominated and observed speeds were found among car drivers than truck drivers. These differences suggest that self-nominated speeds might not be valid indicators of the observed work zone speeds and therefore should not be used as an alternative to observed speed data.     

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.     

Shared road is double happiness: Evaluation of a “Share the road” sign

A road sign with the text «Share the road» and a picture of a smiling cyclist and a passing car was evaluated in a before–after study with surveys among cyclists and car drivers. The sign was set up at two sites on a test road near Oslo in summer 2014. A similar road was used as a comparison. About two thirds of the participants on the test road had noticed the sign. The majority liked it and agreed with its message. Cyclists have more often noticed the sign than car drivers have and they were somewhat more positive towards the sign. Effects on self-reported behavior and the perceived behavior of others were evaluated by comparing changes from the before- to the after-period between test and comparison road. Self-reported behavior of both cyclists and car drivers has improved on the test road after the sign was set up, especially in overtaking situations, and these results are in accordance with how cyclists and car drivers perceived each other’s behavior. The general perception of other road users has improved as well. The results are most likely representative of similar roads with a large proportion of car traffic that is related to recreation and a relatively low level of conflict.     

Analysing the influence of visible roadwork activity on drivers’ speed choice at work zones using a video-based experiment

The present study used a video-based experimental design to investigate the influence of visible roadwork activity on speed preferences at work zones. Four videos from real work zones in Norway were used. Two roadwork areas were filmed at two moments – with and without visible roadwork activity. A total of 815 drivers watched two videos and answered a questionnaire online. Participants stated speed preferences for both videos and then evaluated the influence of 17 common work zone elements on their speed choice. The results showed lower preferred speeds for the videos with visible roadwork activity. The elements considered by drivers to influence their speed included speed regulation (e.g. speed limit signs), transient motives (e.g. time pressure), flow pressure (e.g. speed of the rear driver) and situational conditions (e.g. road situation). Results from the regression analysis showed that visible roadwork activity was the strongest predictor of lower preferred speeds. Speed regulation and transient motives were also significant predictors of preferred speeds. Those who considered speed regulation more important to influence their speed choice at work zones were likely to state lower preferred speeds, while those who considered transient motives as more important were likely to state higher preferred speeds. These findings support the hypothesis that visible roadwork activity is an important factor for lower speed preferences at work zones. The main practical implication is that road authorities should consider various countermeasures to achieve safe driving speeds at work zones, not only roadworks warning signs.     

Effect of chevron design on driver behaviour when encountering and passing through a dangerous curve

Horizontal curves are locations on the road network with a high road accident risk. In order to provide drivers with timely and proper information about the upcoming curve, road authorities often use chevron signs. Although the main design of chevrons is similar in most countries (one colour for the background and another for the arrow), the combination of colours differs. The aim of this simulator study is to investigate how different colour combinations affect drivers when they encounter and drive through horizontal curves on rural roads at daytime. Overall, each of the tested chevrons reduced the driving speed (between 25 and 29 km/h), although not to the speed limit level (60 km/h). However, for curves marked with chevrons with fluorescent or white background the driving speed was the lowest at all measuring points, regardless of the curve direction. The observation of lateral movement shows that there are no significant differences in the way the vehicle is positioned when approaching and driving through curves marked with different chevrons. Based on the obtained results, practical recommendations and potential future research activities are presented.     

The effect of context and drivers’ age on highway traffic signs comprehension

Background: Comprehension of traffic signs is crucial to safety. Objectives: To test the effects of the presentation condition (with or without driving context) on symbolic based road signs comprehension and comprehension time for young and older drivers. Method: 50 young drivers and 50 older drivers were presented with images of 28 Israeli road signs, both without context (with a white background) and in context (with the driving surrounding). Data were collected on the accuracy of signs meaning and on the time it took the participants to provide the meaning. Results: Younger drivers performed significantly better than older drivers on both accuracy and response time (RT). Older drivers’ average RT was approximately twice as long as younger drivers’ RT. However, the presentation mode (with or without context) did not affect sign comprehension of either group, but the presence of the context did increase the time it took the drivers to comprehend the sign’s meaning. In addition, correct response time was similar to opposite to sign’s meaning response time. Implications: Older drivers, can benefit from retraining in sign comprehension of current signage. The training should involve signs in their natural road environment to reduce comprehension time while actually driving. Moreover, signs that were understood as having an opposite meaning should be redesigned or be accompanied by text.     

Examining the self-enhancement bias: professional truck drivers’ perceptions of speed,safety, skill and consideration

A sample of 1006 professional truck drivers were surveyed on their perceptions of self and average other speeds, consideration, relative safety, and relative skill. A disproportionate frequency of responses is found in the measures of speed, safety, and consideration, but not skill. In the measures of speed and consideration this bias is found to operate in a negative direction. Truck drivers are found to evaluate other road users negatively, they do not demonstrate ‘self-enhancement’ indicative of driver overconfidence. Drivers responsible for the biases are isolated from the sample using a method of triangulation. Background factors relating to driver characteristics and employment conditions are examined. Characteristics of the drivers’ employment indicate the perceptions are related to factors external to the drivers’ self-conceptions. These contrasts provide further support for the contention that the ‘self-enhancement bias’, as it appears in this sample, operates as a negative-other rationalisation.     

Does driving experience in video games count? Hazard anticipation and visual exploration of male gamers as function of driving experience

Risk perception and distribution of visual attention while driving are crucial elements for accident prevention and new-driver improvement. This study investigates how racing videogames could shape the visual exploration of virtual and real road in male pre-drivers. The visual performance of players of racing video games with and without driver’s license was tested in virtual vs. real scenarios. Attention to specific elements of different types of road interactions was monitored using an eye-tracking system. Results showed that habitual use of racing video games was not found to foster a positive effect on users’ distribution of visual attention, supporting visual patterns typical of novice drivers. Gamers without driving experience replicated the same patterns in a real road scenario, ignoring road signs and potential areas of interactions with other drivers, while experienced drivers gamers explored video games roads like real roads. The fact that the gamers’ driving performance was not comparable to drivers in the virtual scenario suggests that there are other variables in the gameplay that create a less complex traffic scene, still the visual complexity of different real road interactions is kept in video game interactions, opening new perspectives towards gamers’ visual exploration of the road.     

Do familiarity and expectations change perception? Drivers’ glances and response to changes

The present study shows that repeated exposure to a road environment changes eye movement behaviour. In addition, repeated exposure may result in inadequate responses to unexpected changes in the road environment. Participants drove a low-cost simulator while their eye movements were recorded. With repeated exposure participants’ glances at traffic signs along the route were shorter while having a better recollection of the traffic signs along the route. At the last drive, the priority situation at an intersection was changed (a priority road was changed into a yield situation). Even though drivers glanced at the sign that indicated the new priority situation, they did not sufficiently process the information to show an adequate response. Only two out of 12 drivers showed any response, being a response only after crossing the priority road markings. The current finding that unexpected but relevant information may be missed by drivers is relevant for other monitoring tasks.     

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.     

Familiarity breeds contempt for the road ahead: The real-world effects of route repetition on visual attention in an expert driver

The majority of journeys by car take place on familiar roads, with many routes being driven time and time again. This familiarity has been linked to mind wandering and reduced attention to specific elements of the visual scene (e.g. speed signs). The current study presents on-road eye tracking data from a driving instructor who drove the same route 28 times, incorporating two types of suburban roads, dual and multi-lane carriageways, and a country road. Data reveal a significant positive correlation between the number of times the same route is navigated and off-road dwell time across all five road sections. In addition, route familiarity was associated with decreasing dwell time on safety-relevant aspects of the road ahead in four out of the five sections. These data suggest that route familiarity can lead to undesirable changes in visual attention on real roads, even for expert drivers under observation.     

Comparative assessment of the behaviour of drivers with Mild Cognitive Impairment or Alzheimer’s disease in different road and traffic conditions

The objective of this research was the analysis of the driving performance of drivers with Mild Cognitive Impairment (MCI) or Alzheimer’s disease (AD), in different road and traffic conditions, on the basis of a driving simulator experiment. In this experiment, healthy “control” drivers, patients with MCI, and patients with AD, drove at several scenarios at the simulator, after a thorough neurological and neuropsychological assessment. The scenarios include driving in rural and urban areas in low and high traffic volumes. The driving performance of healthy and impaired drivers was analysed and compared by means of Repeated Measures General Linear Modelling techniques. A sample of 75 participants was analysed, out of which 23 were MCI patients and 14 were AD patients. Various driving performance measures were examined, including longitudinal and lateral control measures. The results suggest that the two examined cerebral diseases do affect driving performance, and there were common driving patterns for both cerebral diseases, as well as particular characteristics of specific pathologies. More specifically, cognitively impaired drivers drive at lower speeds and with larger headway compared to healthy drivers. Moreover, they appear to have difficulties in positioning the vehicle on the lane. The group of patients had difficulties in all road and traffic environments, and especially when traffic volume was high. Most importantly, both cerebral diseases appear to significantly impair reaction times at incidents. The results of this research suggest that compensatory behaviours developed by impaired drivers are not adequate to counterbalance the direct effects of these cerebral diseases on driving skills. They also demonstrate that driving impairments increase as cognitive impairments become more severe (from MCI to AD).