Evaluating the effects of bilingual traffic signs on driver performance and safety

Variable message signs (VMS) can provide immediate and relevant information to road users and bilingual VMS can provide great flexibility in countries where a significant proportion of the population speak an alternative language to the majority. The study reported here evaluates the effect of various bilingual VMS configurations on driver behaviour and safety. The aim of the study was to determine whether or not the visual distraction associated with bilingual VMS signs of different configurations (length, complexity) impacted on driving performance. A driving simulator was used to allow full control over the scenarios, road environment and sign configuration and both longitudinal and lateral driver performance was assessed. Drivers were able to read one- and two-line monolingual signs and two-line bilingual signs without disruption to their driving behaviour. However, drivers significantly reduced their speed in order to read four-line monolingual and four-line bilingual signs, accompanied by an increase in headway to the vehicle in front. This implies that drivers are possibly reading the irrelevant text on the bilingual sign and various methods for reducing this effect are discussed.     

Effects of text space of Chinese-English bilingual traffic sign on driver reading performance

Chinese-English bilingual traffic signs (CEBTS) are widely applied in public spaces within China, but few studies have addressed the spatial arrangement of the two languages on CEBTS and road standards provide little guidance for it. This study investigates whether changes in ‘separating space’, the vertical space between bilingual place names on CEBTS, affects driver reading performance. Ten sign combinations were developed using variations in the sign’s graphic complexity, total number of place names, and the spatial distribution of the place names. Each sign was displayed in a 3D graphics rendered clip of someone driving towards the road sign in random order. Participants identified destinations by reading the signs shown in the clip. The speed and the accuracy of responses was recorded. 39 English-reader participants were recruited and equally split into three groups. Three levels of separating space 0.5H, 0.75H and 1H; H refers to one Chinese character height, were prepared according to a between-subject factorial design. The results show that the separating space affected the response time regardless of sign combinations. Both 0.5H and 0.75H separations caused significant faster reading time and higher accuracy than 1H, but 0.75H appears to achieve better result. The findings contribute to the legibility research concerning bilingual signs with two very different character sets. This study considers improving sign legibility through spatial arrangement of the bilingual text, which is currently limited in the field of Chinese road sign legibility. The findings could inform future standards for Chinese-English road signs.     

The relation between driving experience and recognition of road signs relative to their locations

OBJECTIVES: Examine how driving experience and expectations affect the ability of experienced drivers to identify traffic signs--specifically, no right turn (NRT) and no left turn (NLT) at intersections. BACKGROUND: Failure to heed signs is a frequent cause of accidents, and the authors focused on the contributions of experience and expectancy to sign identification. METHOD: Inexperienced and experienced drivers were connected to an eye tracker system and briefly exposed to various traffic scenes. Some of the pictures included an NRT sign at the expected location (on the right), and some included the same sign at an unexpected location (on the left). The same procedure was used with an NLT traffic sign. RESULTS: Experienced drivers identified traffic signs better than inexperienced drivers did when the signs were posted at the expected location but identified them worse than did inexperienced drivers when they were at unexpected locations. CONCLUSIONS: With experience, drivers' expectations regarding the expected location of traffic signs become so strong that violating these expectancies results in more identification errors among experienced drivers than among inexperienced drivers. To optimize experienced drivers' traffic sign identification, signs must be located in accordance with drivers' expectations--specifically, on the right side of the road. APPLICATIONS: When signs are misplaced, crashes can be caused by inappropriate placement rather than inappropriate driving. Highway designers should ensure that their design conforms to standards that shape experienced drivers' expectations.     

Effects of advertising billboards during simulated driving

There is currently a great deal of interest in the problem of driver distraction. Most research focuses on distractions from inside the vehicle, but drivers can also be distracted by objects outside the vehicle. Major roads are increasingly becoming sites for advertising billboards, and there is little research on the potential effects of this advertising on driving performance. The driving simulator experiment presented here examines the effects of billboards on drivers, including older and inexperienced drivers who may be more vulnerable to distractions. The presence of billboards changed drivers’ patterns of visual attention, increased the amount of time needed for drivers to respond to road signs, and increased the number of errors in this driving task.     

A driving-emulation task to study the integration of goals with obligatory and prohibitory traffic signs

This research aims to analyse how drivers integrate the information provided by traffic signs with their general goals (i.e. where they want to go). Some previous studies have evaluated the comparative advantages of obligatory and prohibitory traffic signs using a judgement task. In this work, a new experimental task with greater similarity to driving situations is proposed. Participants imagine they are driving a vehicle and must make right or left turn manoeuvres according to a previously indicated objective and the information from obligatory and prohibitory traffic signs. Eighty-two participants took part in two different experiments. According to the results, an obligatory traffic sign is associated with faster and more accurate responses only when the participant's initial objective is allowed. When the initial objective was not allowed, an advantage in accuracy was observed with prohibitory traffic signs and there was no significant difference in reaction time between the two types of sign. These results suggest that having an obligatory traffic sign may facilitate a correct response when the driver's goal is effectively allowed, whereas a prohibitory traffic sign could be more effective in preventing error when the driver has a not-allowed goal in mind. However, processing a prohibitory sign requires an extra inference (i.e. deciding which is the allowed manoeuvre), and thus the potential advantage in reaction time of the prohibitory sign may disappear. A second experiment showed that the results could not be explained by a potential congruency effect between the location (left or right) of the road signs and the position of the key or the hand used to respond (such as the Simon effect or the spatial Stroop effect). Also, an increase in the difficulty of the task (using an incongruent hand to respond) affected performance more strongly in experimental conditions that required making inferences. This made the advantage of the obligatory sign over the prohibitory sign in this condition more noteworthy. The evidence gathered in the current study could be of particular interest in some applied research areas, such as the assessment of road traffic signalling strategies or the ergonomic design of GPS navigation systems.     

On-line driver workload estimation. Effects of road situation and age on secondary task measures

In order to develop a driver-car interface that adapts the presentation of messages generated by in-vehicle information systems to driver workload, two experiments investigated potential determinants of driver visual and mental workload as indicated by performance on two secondary tasks. Experiment 1 suggested that road situation is a major determinant of visual and mental workload of the driver and that the processing resources of older drivers are somewhat more limited than those of younger and middle-aged drivers. Familiarity with the area of driving (when guided) and time of day (associated with traffic density) showed no secondary task effects. Experiment 2 showed that the categorization of road situations, proposed in Experiment 1, could underlie adaptation of visually loading messages to the workload incurred by driving. This was not found with respect to mentally loading messages.     

On-line driver workload estimation. Effects of road situation and age on secondary task measures

In order to develop a driver-car interface that adapts the presentation of messages generated by in-vehicle information systems to driver workload, two experiments investigated potential determinants of driver visual and mental workload as indicated by performance on two secondary tasks. Experiment 1 suggested that road situation is a major determinant of visual and mental workload of the driver and that the processing resources of older drivers are somewhat more limited than those of younger and middle-aged drivers. Familiarity with the area of driving (when guided) and time of day (associated with traffic density) showed no secondary task effects. Experiment 2 showed that the categorization of road situations, proposed in Experiment 1, could underlie adaptation of visually loading messages to the workload incurred by driving. This was not found with respect to mentally loading messages.     

A simulated study on the effects of information volume on traffic signs, viewing strategies and sign familiarity upon driver''s visual search performance

A two-stage simulation experiment was conducted to investigate the effect of information volume on traffic regulatory/road direction signs, drivers’ viewing strategies and sign familiarity on performance in visual search. In Stage I experiment, the amount of information on a total of 187 traffic regulatory and 1272 road direction signs was calculated and divided into five information levels using cluster analysis. In Stage II experiment, 24 subjects participated in a 2 (familiarity)×5 (information volume level)×2 (viewing strategy) mixed factorial experiment. Each subject was required to perform a visual search task and a question-and-answer (Q&A) task. Visual search time and number of correct responses collected serve as the objective dependent variables. Subjective workload related to time stress and visual effort was gathered through a modified three-point rating. Results show that information volume on traffic signs had significant impact on drivers’ visual search performance. Generally, the greater the amount of information, the slower the drivers in visual search are. However, while drivers had the highest accuracy rate in remembering purely pictorial traffic signs, these signs within the smallest information volume level required a relatively longer search time. Different viewing strategies also led to different performances. The back-and-forth strategy yielded better search performance than the fixed strategy. Subjective workload evaluation indicates that drivers with less sign familiarity will be under greater time/visual pressures. Guidelines for designing for traffic signs or in-vehicle signing systems are provided.

Relevance to industry

This study calculated the amount of information on traffic signs and compared the effects of different information volume on drivers’ visual search performance. The results can provide guidelines for traffic sign designers to help decide on the presentation format for in-vehicle signing information systems.     

Recently qualified drivers: a comparison of two methods of driving instruction

The progress of drivers in the year after passing the driving test has been evaluated in a number of studies undertaken in France and elsewhere. These studies have focused upon the technical and psychological difficulties that newly qualified drivers need to overcome before they come to consider themselves, and to be considered by others, as fully competent drivers. The quality of driving instruction seems to be crucial in determining the kinds of problems which new drivers must face and the time taken to achieve mastery.

Two methods of driving instruction were compared in terms of the problems encountered by learners after passing their driving test. The subjects were 170 drivers taught by the traditional ‘driving-test’ method and 269 who had taken an accelerated course of intensive instruction. Each driver was sent a series of questionnaires during the 10 months after they qualified. In addition to this form of continuous survey, an in-depth study of nine other new drivers was undertaken over the same period; their on-the-road behaviour was used to supplement information obtained from the questionnaires. The results of the research are discussed in relation to a variety of factors: level of driver confidence; ease of vehicle handling; problems acknowledged by drivers; drivers’ attitude towards road safety; progress made in the period following the driving test; need for further instruction; response to frustration and evaluation of aggressive tendencies.     

Curve negotiation performance in a driving simulator as a function of curve geometry

A study was conducted to investigate driver performance on curves. The between-trial factors were Blood Alcohol Content (BAC) level (0.00, 0.7, 0.12 %) and type of driving scenario (eventful versus uneventful). The within-session factors were edgeline width, type of curve-warning sign, and curve type. Twelve male drivers drove continuously for two hours on each of three nights. Each subject negotiated 150 curves during each two-hour drive. Curve radii ranged from 57.3 to 94.2 m (188 to 309.2 ft). Advisory speeds presented on curve-warning signs ranged from 32.2 to 72.4 km/h (20 to 45 mile/h). The driving simulator was a completely instrumented cab resting on a fixed base. The results showed that curve-entry speed increased as radius of curvature increased. Lateral position error was greater on the curve with the smallest radius and least on the curve with the shortest length. Heading error first increased then decreased as curve radius increased. Neither the amount of road used nor the mean computed lateral acceleration were related to curve radius, heading change or length. These results are attributed to the absence of lateral-acceleration cues in the driving simulator.     

Insurance Classifications and Drivers' Galvanic Skin Response

Drivers' galvanic skin responses were recorded in town traffic and on country roads. Two groups of drivers were compared, those who would pay higher insurance premiums, by reason of their ago or occupation, and the rest. The high insurance group did not differ from the rest in the magnitude of the GSR. but when the ratio of the GSR in town traffic to that on a country road was considered there was a significant difference such that the high insurance group had a relatively greater GSR on the country road.

It is suggested that in town traffic most of the GSR arc generated by the actions of other drivers, whereas on the open road the GSRs are self generated by the subjects' driving. The GSR on the open road will therefore be more affected by the individual method of driving and by the risks the driver takes. The ratio of town GSR to country GSR can be used to eliminate the large unexplained differences between subjects and to expose the differences in driving behaviour     

Good intentions: drivers’ decisions to engage with technology on the road and in a driving simulator

Distraction-related accidents are, more often than not, due to the drivers’ voluntarily engagement with a secondary task. Therefore, the strategic management of in-vehicle tasks and the drivers’ decision to engage with them is an important aspect of the driver distraction phenomenon that needs to be addressed. While the consequences of distracting tasks are often assessed in settings where the risk of engaging is reduced (i.e., simulators), the drivers’ decision to engage with secondary tasks is often ignored. This study assessed the drivers’ decision to engage with secondary tasks using verbal protocols to provide insights into the drivers’ intention within a naturalistic driving setting, on the road, and in a simulated driving environment. This enabled an understanding of when drivers engage with technological distractions, why they choose to do so, as well as how they may go about doing it. Different road types were found to differentially impact the drivers’ intention to engage, as did the types of secondary tasks, with some tasks having an increased willingness to engage compared to others. Factors that increase and/or reduce the likelihood of engaging are presented. The decisions that drivers made to engage with secondary tasks in the simulator were found to correlate strongly to their decision to so on the road. This provides support for the use of simulators when assessing the drivers’ decision to engage with secondary tasks. The effect of verbal protocols on the drivers’ speed metrics was assessed to determine how they may have affected their driving performance.     

Drivers and Road Signs: A Preliminary Investigation of the Capacity of Car Drivers to get Information from Road Signs

It was found that the mean percentage of road signs recorded by five subjects over the course of a 105 miles long car journey under optimal conditions was of the order of 90 per cent of signs passed.

It was found that the mean percentage of drivers recording a road sign was 47 per cent of those passed it. (This figure is based on percentages obtained for five different road signs, the number of drivers involved being about 1000.). On analysing the data for these five signs, it was found that there was a significant difference between the percentage of drivers recording each one. This difference was postulated as being due to the degree of urgency of the information contained in each sign (as based on past experience), i.e. the more urgent the information, the higher the percentage of drivers recording the sign.     

Haptic gas pedal feedback

Active driver support systems either automate a control task or present warnings to drivers when their safety is seriously degraded. In a novel approach, utilising neither automation nor discrete warnings, a haptic gas pedal (accelerator) interface was developed that continuously presents car-following support information, keeping the driver in the loop. This interface was tested in a fixed-base driving simulator. Twenty-one drivers between the ages of 24 and 30 years participated in a driving experiment to investigate the effects of haptic gas pedal feedback on car-following behaviour. Results of the experiment indicate that when haptic feedback was presented to the drivers, some improvement in car-following performance was achieved, while control activity decreased. Further research is needed to investigate the effectiveness of the system in more varied driving conditions. Haptics is an under-used modality in the application of human support interfaces, which usually draw on vision or hearing. This study demonstrates how haptics can be used to create an effective driver support interface.     

Elderly and young driver's reaction to an in-car enforcement and tutoring system

A system that contrasts driver behaviour with normative behaviour was tested in an advanced driving simulator. Drivers were provided with auditory and visual tutoring messages if deviations were detected from normative, i.e. legally allowed behaviour with respect to a selection of offences. Results showed that the system was very effective in increasing law-abiding behaviour, which has a major positive effect on traffic safety. However, driver mental effort, as indicated by self-reports and drivers' physiological states, was slightly increased in conditions where drivers received feedback. Opinion about the tutoring system was positive in terms of usefulness. Self-reports on satisfaction differed between age groups; young drivers rated it low, while elderly drivers held a positive attitude.     

An investigation of train driver visual strategies

Train driving is primarily a visual task; train drivers are required to monitor the dynamic scene visually both outside and inside the train cab. Poor performance on this visual task may lead to errors, such as signals passed at danger. It is therefore important to understand the visual strategies that train drivers employ when monitoring and searching the visual scene for key items, such as signals. Prior to this investigation, a pilot study had already been carried out using an eye tracking technique to investigate train drivers’ visual behaviour and to collect data on driver monitoring of the visual environment, Groeger et al. (2003) Pilot study of train drivers’ eye movements, University of Surrey. However, a larger set of data was needed in order to understand more fully train driver visual behaviour and strategies. In light of this need, the Transport Research Laboratory produced a methodology for the assessment of UK train driver visual strategies, on behalf of the Rail Safety and Standards Board and applied this methodology to conduct a large-scale trial. The study collected a wealth of data on train drivers’ visual behaviour with the aim of providing a greater understanding of the strategies adopted. The corneal dark-eye tracking system chosen for these trials tracks human visual search and scanning patterns, and was fitted to 86 drivers whilst driving in-service trains. Data collected include the duration and frequency of glances made towards different elements of the visual scene. In addition, the train drivers were interviewed after driving the routes, to try and understand the thought processes behind the behaviour observed. Statistical analysis of over 600 signal approaches was conducted. This analysis revealed that signal aspect, preceding signal aspect, signal type and signal complexity are important factors, which affect the visual behaviour of train drivers. Train driver interview data revealed that driver expectation also plays a significant role in train driving. The findings of this study have implications for the rail industry in terms of infrastructure design, design of the driving task and driver training. However, train driving is extremely complex and the data from this study only begin to describe and explain train driver visual strategies in the specific context of signal approaches. This study has provided a wealth of data and further analysis of it is needed to investigate the role of other factors and the complex relationships between factors during signal approaches and other driving situations systematically. Finally, there are important aspects of visual behaviour that cannot be examined using these data or this method. Investigation of other aspects of visual behaviour, such as peripheral vision, will require other methods such as simulation.     

Haptic gas pedal feedback

Active driver support systems either automate a control task or present warnings to drivers when their safety is seriously degraded. In a novel approach, utilising neither automation nor discrete warnings, a haptic gas pedal (accelerator) interface was developed that continuously presents car-following support information, keeping the driver in the loop. This interface was tested in a fixed-base driving simulator. Twenty-one drivers between the ages of 24 and 30 years participated in a driving experiment to investigate the effects of haptic gas pedal feedback on car-following behaviour. Results of the experiment indicate that when haptic feedback was presented to the drivers, some improvement in car-following performance was achieved, while control activity decreased. Further research is needed to investigate the effectiveness of the system in more varied driving conditions. Haptics is an under-used modality in the application of human support interfaces, which usually draw on vision or hearing. This study demonstrates how haptics can be used to create an effective driver support interface.     

Effects of using head-up display in automobile context on attention demand and driving performance

This study aimed to investigate the difference in driving performance between drivers’ attention on the head-up display (HUD)/road under low/high road conditions via a driving simulator experiment. Experimental driving included four driving scenarios with attention-on-the-HUD followed by attention-on-the-road or vice versa under high or low driving load conditions. Each scenario took about a 30-min driving consisting of two 15-min sections for each attention location. Forty-eight participants, divided into four groups, drove one of the four scenarios once. Besides driving safely within speed limit, participants were also required to perform detection task and speed limit sign response task. Results revealed that drivers paying attention to the HUD, under both low and high driving load conditions, reacted faster to speed limit sign changes than when paying attention to the road. In addition, attention-to-the-HUD under low driving load condition caused the smallest variation in steering wheel angle and lateral acceleration. These differences can be attributed to the driver's enhanced awareness and the cognitive capture effect, and tended to diminish with increasing driving workload. Finally, attention shift of drivers and the so-called novelty effect for using new technology product were also found.     

Influence of age and proximity warning devices on collision avoidance in simulated driving

OBJECTIVE: We conducted a set of experiments to examine the utility of several different uni- and multimodal collision avoidance systems (CASs) on driving performance of young and older adult drivers in a high-fidelity simulator. BACKGROUND: Although previous research has examined the efficacy of different CASs on collision avoidance, there has been a dearth of studies that have examined such devices in different driving situations with different populations of drivers. METHOD: Several different CAS warnings were examined in varying traffic and collision configurations both without (Experiment 1a) and with (Experiment 2) a distracting in-vehicle task. RESULTS: Overall, collision avoidance performance for both potential forward and side object collisions was best for an auditory/visual CAS, which alerted drivers using both modalities. Interestingly, older drivers (60-82 years of age) benefited as much as younger drivers from the CAS, and sometimes they benefited more. CONCLUSION: These data suggest that CASs can be beneficial across a number of different driving scenarios, types of collisions, and driver populations. APPLICATION: These results have important implications for the design and implementation of CASs for different driver populations and driving conditions.