Influence of traffic conditions on driver behavior before making a right turn at an intersection: Analysis of driver behavior based on measured data on an actual road

This paper describes an investigation of the influence of the position of a forward vehicle and following vehicle on the onset of driver preparatory behavior before making a right turn at an intersection. Four experimental vehicles with various sensors and a driving recorder system were developed to measure driver behavior before making a right turn at a specific intersection on a public road. The experimental term was eight weeks to collect data on natural driving maneuvers. The relationships between the remaining distances to the center of the intersection when releasing the accelerator pedal, moving the right foot to cover the brake pedal, and activating the turn signal and the relative distances from the forward and following vehicles were analyzed based on the measured data. The time it took to reach the center of the turn and the driving speed when each behavioral event occurred were also evaluated from the viewpoint of the relative position between the driver’s vehicle and the leading or following vehicles. The results suggest that the drivers approached the target intersection in a car-following condition, and that the positions of the front and rear vehicles and the vehicle velocity influence the onset location and timing of releasing the accelerator pedal and covering the brake pedal. Drivers began to decelerate closer to the center of the intersection when they approached the intersection close to a leading or following vehicle at a reduced driving speed. However, these influences were not reflected in the turn signal operation, indicating that drivers intend to make a right turn at a constant location while approaching a target intersection and that intention appears in the turn signal activation. The findings of this observational study imply that the method of providing route guidance instruction, in which the traffic conditions surrounding the driver’s vehicle are taken into consideration, is effective in reducing driver errors in receiving instruction and following the correct route. The results also indicate that measuring and accumulating different behavioral indices based on traffic conditions contribute to determining the criteria for the presentation timing just before reaching the intersection, which can assist drivers in preparing to make a right turn at a usual location. Driver decelerating maneuvers are used while driving without leading or following vehicles and while driving with a lead and/or following vehicle at long range, and driver turn signal operations are used when approaching an intersection under close car-following conditions.     

The tendency of drivers to pass other vehicles

The purpose of this study was to assess the speed differential threshold—if there is one—at which drivers decide to pass a lead vehicle. Drivers in a simulator encountered vehicles in front that were programmed to travel at speeds that were similar, slightly below, or even slightly above the drivers’ own speed. The study involved a total of 152 such passing opportunities. In almost all of the encounters with slower vehicles (traveling at speeds slower than 3 km/h of the driver) they passed them, and in two thirds of the encounters when the lead vehicles were moving at their speed they passed them too. Most surprising was that in 50% of the encounters drivers passed the lead vehicle when it was traveling faster than their average speed. In these situations drivers actually increased their own speed substantially to accomplish the passing maneuver, despite the fact that not passing the lead vehicle would not have caused any delays. The tendency to pass appears to be related to the drivers’ own speed variability: the more variable the driver’s speed the more likely he or she was to pass the vehicle ahead even when its speed was greater than their average speed. The results are interpreted in terms of (a) driver aggression, and (b) association of car following with added effort, attention overload, or risk. The latter explanation implies that the tendency to pass vehicles may be reduced with the introduction of in-vehicle technologies such as adaptive cruise control.     

Feedback and driver situation awareness (SA): A comparison of SA measures and contexts

The dominant technological trajectory in vehicle design brings with it similarly dominant driver performance issues in regard to vehicle feedback and driver situational awareness (SA). Three experiments are reported in this paper that describe not only the effects on driver SA of manipulations of vehicle feedback but also illuminate issues concerned with SA measurement methods and contexts. The findings suggest that current trends in vehicle design may contribute little towards a driver’s SA and, in fact, may actually show a generalized trend towards decreasing it. The efficacy of verbal protocol and probe recall SA measurement techniques is noted in terms of observing this effect. On the other hand, a concerning dissociation occurred with findings from a self-report measure of SA. Drivers appear to show a concerning lack of self-awareness of their SA and, indeed, any shortfall in it.     

Efficacy and feeling of a vibrotactile Frontal Collision Warning implemented in a haptic pedal

A haptic pedal has been designed to emulate the behaviour of a common vehicle pedal and render superimposed vibrations with different characteristics. It was installed in a driving simulator, as an accelerator pedal with the secondary function of a vibrotactile Frontal Collision Warning (FCW). The efficacy and feeling of this solution was tested with 30 subjects using vibrotactile signals with 0.50, 1.05, and 1.60 Nm, at 2.5, 5, and 10 Hz, against a baseline visual FCW. Participants had to match the speed of a leading vehicle when the FCW was triggered. Their braking response was evaluated in terms of brake reaction time, matching speed time, control of velocity and headway reduction. Driver’s feelings were assessed with Kansei methodologies. Haptic stimuli were found to be more effective than visual signals, and the characteristics of the vibration also influenced the results. The best performance was achieved at the maximum amplitude, and in the range between 5 and 10 Hz. The perceived functionality and discomfort followed a trend coherent with the objective measurements. The conclusions of this study may be applied to develop effective and safe warning systems in vehicles, limiting the annoyance that they might cause to drivers.     

Lifestyle traits as predictors of driving behaviour in urban areas of Greece

The aim of this study was to examine possible links between different lifestyle patterns and aberrant driver’s behaviour. Personal interviews were conducted in a representative sample of 324 adults (18–65), all residents of Crete. Aberrant driver’s behaviour was assessed by the ‘driver behaviour questionnaire’ (DBQ). Also to measure different dimensions of lifestyle, first, a 26-items questionnaire was used, and second, three questions measuring ‘driving without destination’, related in previous findings with road accident risk. Four lifestyle patterns: ‘religion/tradition’, ‘driving aimlessly’, ‘sports’ and ‘culture’ are significant predictors of ordinary violations. ‘Driving without destination’ has a significant effect all three DBQ factors (b positive). ‘Religion/tradition’ was related only to ordinary violations (b negative) and ‘sports’ has a positive impact on ordinary violations and a negative impact on ‘errors’. Two lifestyle factors are related to more dangerous driving: ‘Driving without destination’ and/or pursuing a more ‘athletic way of living’. Road safety campaigns must teach the first group to use other hobbies and activities to vent their feelings and the second, not to overestimate their abilities, while driving.     

Compensating for failed attention while driving

While operating a motor vehicle, drivers must pay attention to other moving vehicles and the roadside environment in order to detect and process critical information related to the driving task. Using a driving simulator, this study investigated the effects of an unexpected event on driver performance in environments of more or less clutter and under situations of high attentional load. Attentional load was manipulated by varying the number of neighboring vehicles participants tracked for lane changes. After baseline-driving behavior was established, the unexpected event occurred: a pedestrian ran into the driver’s path. Tracking-accuracy, brake initiation, swerving, and verbal report of the unexpected pedestrian were used to assess driver performance. All participants verbally reported noticing the pedestrian. However, analyses of driving behavior revealed differences in the reactions to the pedestrian: drivers braked faster and had significantly less deviation in their steering heading with a lower attentional load, and participants in low clutter environments had a larger overall change in velocity. This research advances the understanding of how drivers allocate attention between various stimuli and the trade-offs between a driver’s focus on an assigned task and external objects within the roadway environment. Moreover, the results of this research lend insight into how to construct roadway environments that encourage driver attention toward the most immediate and relevant information to reduce both vehicle-to-vehicle and vehicle-to-pedestrian interactions.     

Testing for effects of racial attitudes and visual contrast on the speed of a driver’s response to a pedestrian

Although ethnic minorities are overrepresented in pedestrian-vehicle collisions, previous driving studies did not examine racial attitudes in such collisions. Our objective was to determine whether the speed of a driver’s response to a pedestrian was affected by the driver’s racial attitudes and the contrast between the pedestrian’s skin colour and background. Participants viewed simulated driving scenes of a pedestrian on a road and pressed a button as soon as they saw an obstacle. Visual information, but not racial attitudes, affected the time it took observers to respond to pedestrian and non-pedestrian stimuli in driving scenes. Results indicated that contrast affected response time even when the stimulus was subliminal. We believe this is the first demonstration of contrast effects with subliminal stimuli in a driving context. Results have implications for traffic safety and for methodology used to study racial attitudes.     

Central interference in driving: is there any stopping the psychological refractory period?

ABSTRACT— Participants attempted to perform two tasks concurrently during simulated driving. In the choice task, they responded either manually or vocally to the number of times a visual or auditory stimulus occurred; in the braking task, they depressed a brake pedal in response to the lead car's brake lights. The time delay between the onset of the tasks' stimuli, or stimulus onset asynchrony (SOA), was varied. The tasks were differentially affected by the manipulations. Brake reaction times increased as SOA was reduced, showing the psychological refractory period effect, whereas the choice task showed large effects of the stimulus and response modalities but only a small effect of SOA. These results demonstrate that a well-practiced "simple" task such as vehicle braking is subject to dual-task slowing and extend the generality of the central-bottleneck model.     

Analyzing drivers’ crossing decisions at unsignalized intersections in China

In China, when two vehicle drivers encounter at an unsignalized intersection, almost neither of them completely stops the vehicle. Instead, one gradually approaches and dynamically makes a decision to either yield or preempt by gaming with the other vehicle. This process generates traffic conflicts and increases the probability of accidents. In this study, we aimed to study how straight-moving drivers made preemptive/yielding decisions when they encountered other drivers straight-moving across at unsignalized intersections. A total of 150 crossing cases were collected at an unsignalized intersection in Kunming City, China. By using detection program we made, motion parameters of the vehicles were extracted. Classification tree analysis was used to identify the decision moment of drivers and the major motion parameters that affected their decisions. Results showed that for crossing processes at unsignalized intersections in China, straight-moving drivers from the right side made preemptive/yielding decisions from 0.9 s to 1.3 s before reaching the crossing point. However, straight-moving drivers from the left side made decisions from 0.9 s to 1.2 s before reaching the crossing point. The speed difference between the two vehicles was the most important factor that affected a driver’s decision-making. If the vehicle driver from the right side drove significantly slower than that from the left, then most drivers from the right side would yield to those from the left. On the contrary, if the vehicle driver from the right side drove significantly faster than that from the left, then most drivers from the right side would preempt those from the left. The findings of this study will help understand the decision-making patterns of drivers under crossing conditions, and thus provide suggestions to improve drivers’ behavior at unsignalized intersections in China.     

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.     

Pedestrians at the kerb – Recognising the action intentions of humans

Aim of the presented research is the development of a cognitive driver assistance system, which can capture the traffic situation, analyse it, and warn the driver in case a pedestrian is a potential hazard. Hence parameters have to be identified by which the intention of the pedestrian can be unambiguously predicted. Two approaches to the topic are addressed. First, the pedestrian’s perspective was taken. The question was how crossing decisions were influenced by the parameters distance and velocity of the car. Following a signal, participants had to choose to cross the road in front of or behind the car. The data analysis showed that pedestrians relied on the distance of the car rather than the time to collision for their decision. In the second experiment the observer’s perspective raised the question what parameters humans use to predict pedestrians’ intentions. Videos of natural traffic scenes were presented. Participants had to make statements about whether the shown pedestrian would cross the street during the next moment. In a baseline and four experimental conditions, certain information was masked in the videos. Just the condition in which only the trajectory information of the pedestrian was available produced a higher error rate.     

The effect of cellular telephone conversation and music listening on response time in braking

Driver distraction contributes to vehicle accidents, with estimates as high as one-half of crashes being distraction-related. The purpose of this experiment was to explore potential distractions by testing the effects of cellular telephone conversation and music listening on response time and its subcomponents of reaction time (RT) and movement time (MT) in a simulated braking task. Participants (N = 27) sat at a simulated driving station and released the accelerator and depressed the brake pedal as quickly as possible following activation of a simulated brake lamp. The braking task was performed under each of six conditions including: (a) the control (braking task only); (b) music playing at 66 dBA; (c) music playing at 78 dBA; (d) cellular telephone conversation; (e) cellular telephone conversation and music at 66 dBA; and (f) cellular telephone conversation and music at 78 dBA. Cellular telephone conversation slowed response time, yet music had no effect on response time. While the RT results generally mirrored those of response time (i.e., RT was also slowed by the telephone conversation), interestingly, MT was actually faster when the cellular telephone conversation was present compared to when it was not. Participants appear to have anticipated slower RT in the presence of the cellular telephone conversation, and attempted to compensate by executing a more rapid movement to the brake pedal.     

Influence of following vehicle’s tailway and classification on subject driver’s response to the circular yellow indication

Traffic crashes at signalized intersections are frequently linked to driver behavior at the onset of the circular yellow (CY) indication. To better understand behavioral factors that influence a driver’s decision to stop or go at an intersection, this study analyzed the behavior of the driver of a subject vehicle at the onset of the CY indication. Driver performance data from 53 participants were collected in the Oregon State University Driving Simulator, simulating scenarios of driving through high-speed intersections under various conditions. Data included interactions where the driver stopped at the stop line (n = 644) or proceeded through the intersection (n = 628) in response to a CY indication. Data were analyzed as panel data while considering 12 indicator variables related to the driver’s stop/go decision. These indicator variables included time to stop line (TTSL), tailway time, following vehicle type, vehicle speed at the onset of the CY indication, and demographics (age, gender, driving experience, level of education, personal vehicle type, number of times driving per week, number of miles driving last year, participation in previous simulation studies. A random-parameter binary logit model was used to determine contributing factors for driver decision making at the onset of CY indication while accounting for unobserved heterogeneity. Four indicator variables were significantly related to the driver’s stop/go decision, but three factors varied across observations. Findings showed that a driver’s stop/go decision in response to a CY indication was associated with the time to the stop line (TTSL), tailway time to the following vehicle, subject vehicle speed at the onset of the CY indication, and driver’s age (20–36 years), but was not significantly associated with classification of the following vehicle. Also, the findings indicated that a shorter tailway increased a subject driver’s red-light running frequency. These findings provide insights into variables that affect driver decisions in a vehicle-following situation at the onset of the CY indication. This information can help make better decisions in smart traffic control systems such as to extend/decrease the green interval slightly to avoid decisions that are more difficult.     

The time course of a lane change: Driver control and eye-movement behavior

In this paper we explore the time course of a lane change in terms of the driver's control and eye-movement behavior. We conducted an experiment in which drivers navigated a simulated multi-lane highway environment in a fixed-base, medium-fidelity driving simulator. We then segmented the driver data into standardized units of time to facilitate an analysis of behavior before, during, and after a lane change. Results of this analysis showed that (1) drivers produced the expected sine-wave steering pattern except for a longer and flatter second peak as they straightened the vehicle; (2) drivers decelerated slightly before a pass lane change, accelerated soon after the lane change, and maintained the higher speed up until the onset of the return lane change; (3) drivers had their turn signals on only 50% of the time at lane-change onset, reaching a 90% rate only 1.5–2 s after onset; (4) drivers shifted their primary visual focus from the start lane to the destination lane immediately after the onset of the lane change. These results will serve as the basis for future development of a new integrated model of driver behavior.     

Using spatial vibrotactile cues to direct visual attention in driving scenes

We report two experiments designed to investigate the potential use of vibrotactile warning signals to present spatial information to car drivers. Participants performed an attention-demanding rapid serial visual presentation (RSVP) monitoring task. Meanwhile, whenever they felt a vibrotactile stimulus presented on either their front or back, they had to check the front and the rearview mirror for the rapid approach of a car, and brake or accelerate accordingly. We investigated whether speeded responses to potential emergency driving situations could be facilitated by the presentation of spatially-predictive (80% valid; Experiment 1) or spatially-nonpredictive (50% valid; Experiment 2) vibrotactile cues. Participants responded significantly more rapidly following both spatially-predictive and spatially-nonpredictive vibrotactile cues from the same rather than the opposite direction as the critical driving events. These results highlight the potential utility of vibrotactile warning signals in automobile interface design for directing a driver’s visual attention to time-critical events or information.     

The impact of age on useful visual field deterioration and risk evaluation in a simulated driving task

The primary goal of this study is to evaluate whether the driver can estimate his performance and the deterioration of his state of alertness during a simulated driving task. The second goal is to study the relation between useful visual field (UVF) deterioration and the capacity to estimate performance in a visual task and the decrease of level of alertness as a function of age. In our experiment, two groups of subjects: 10 drivers between 21 and 34 years old and nine drivers between 46 and 57 years old were required to follow a vehicle in a simulated road traffic situation for 2 hours. In addition, the driver had to detect the change of colour of a signal located in the central part of his visual field or a peripheral signal appeared on the rear light of one of the vehicles in the traffic. The analysis of data collected during this visual task confirms that UVF deteriorates with the duration of the driving task and with the driver's age. The analysis of subjective data related to the state of alertness highlights an effect both of age and of the moment when this self-evaluation was carried out. However, self-evaluation of the subject's performance does not depend on driver's age. Finally, the study shows that the correlation between objective data (performance of visual task) and subjective data (state of drowsiness and self-evaluation of performance of the visual task) is low, and the implications with regard to road safety are discussed.     

A model for explanation of personal attitudes toward traffic of candidate drivers attending drivers’ courses: Risky candidate driver’s attitude model

There exist a good many scientific studies into risk-taking and risky behavior displayed by reckless drivers; however, there are only a few studies into attitudes towards the traffic displayed by candidate drivers. The present study aims to investigate the dimensionality of candidate attitudes’ drivers. Data were collected from questionnaire completed by 258 candidate drivers, and were divided into two sets. The first data was used to explore the underlying factor structure and five latent factors were derived; Factor A Attitude towards drinking and driving; Factor P positive attitude toward traffic; Factor S speeding; Factor T traffic flow vs. rule obedience; and Factor R risky candidate driver’s attitude. The second data set was used to confirm this factorial structure using confirmatory factor analysis. The fit indices showed that the model fitted the data well.     

An integrated device to evaluate a driver’s functional state

In the field of cognitive ergonomics, research on car drivers requires multimodal in-vehicle systems for recording not only driving-related behavior, but also contextual information from their surroundings. In addition, reliable information concerning a driver’s functional state should be obtained. In this article, we describe an integrated device simultaneously recording specific physiological data, video recordings of the driver and environment, parameters from the vehicle, and contextual data. Physiological signals from the autonomic nervous system provide objective and quantitative information on the driver’s alertness and his/her ability to process specific driving-related stimuli or other nonspecific information. Consequently, recorded physiological responses can be related to individual driving events. Electrodermal and cardiac activities are sensitive to time-dependent variations in arousal level and to certain external stimuli, so there is great interest in studying drivers’ behavior via measured physiological signals that have been established as suitable behavioral indicators. The present integrated device is capable of processing the relevant indices from raw measured data in real time.     

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.     

Analysing driver’s decision in dilemma zone at signalized intersections under disordered traffic conditions

Delay in the decision-making process of stop or go during the amber phase of the signal cycle often leads to abrupt hard deceleration or red light violations at signalized intersections. The indecisiveness or the dilemma in decision making often results in compromised safety of the road users. The present study attempts to analyze the driver’s behaviour in order to make the decision of stop or go and developed a binary logistic regression model while considering different traffic behaviour parameters exhibited and observed after the onset of the amber phase. Empirical vehicular trajectory data from three signalized intersections covering 121 signal cycles and 1347 vehicles are used in the study. The study presents two dilemma zone identification models based on distance from the stop line, focusing on easy-to-use and static driver assistance and dynamic-realtime driver assistance systems. Both the models are observed to show good fit and prediction accuracy. The models are validated internally and externally for their adaptability in the field. The effect of different traffic parameters on the dilemma zone is explored, and a possible real-time application of the dynamic model as a driver assistance system in decision-making is explored.