Impact of the geometric field of view on drivers’ speed perception and lateral position in driving simulators

Driving simulators have become an effective tool in road safety research. In recent years, the validity of simulators raised debates concerning the extant to which driving in the simulator resembles driving in the reality. Different types of driving simulators with different characteristics have been developed to study driver behavior, however, the fidelity and reliability of such systems are questionable if no proper validation is conducted. Regarding the visual aspect, the fidelity of the simulators can be assessed based on the field of view of the simulator screens. Drivers’ speed perception and lateral position were compared for two different geometric field of view (GFOV) angles (i.e., 60 and 135 degrees). Results from the ANOVA tests showed that drivers highly underestimate their driving speed while driving for the condition with 60 degrees of GFOV compared to the condition with 135 degrees of GFOV. Furthermore, drivers drove closer to the real-world situations in the condition with 135 degree of GFOV compared to the condition with 60 degree. Results of this study suggest that, using incorrect GFOV for any simulator would generate biased results in speed and lateral position. Therefore, a proper calibration criterion of the GFOV for the simulators is essential. This study recommends using a scale factor (GFOV/FOV) of 1.00 for virtual environment offered by the simulation scenarios such as GFOV of 135 degree for simulators having three screens with 135 degree of field of view (FOV)

Empirical evaluation of drivers’ start-up behavior at signalized intersection using driving simulator

Start-up behavior at signalized intersection mainly depends on perception reaction time of drivers to the green phase. This study investigated the start-up behavior at signalized intersections by considering reaction time, acceleration and jerk (the rate of change of acceleration) of drivers in the state of Qatar. Distributions for reaction time, acceleration and jerk were plotted and the mean and 50th percentile values were presented. Three demographic factors (i.e., gender, ethnicity and age) were analyzed using two-tailed/unpaired t-tests. The relationships between acceleration and reaction time, and jerk and reaction time were investigated by linear regression analyses. Descriptive analysis showed that drivers had a mean reaction time of 2.91 s. Furthermore, Arab drivers had significantly lower reaction time than non-Arab drivers. Regarding the jerk maneuvers, young drivers (below 30 years) displayed significantly higher jerk than drivers of 30 years or above. Results from linear regressions showed significant negative correlations in both models (i.e., reaction time on acceleration, reaction time on jerk). As this study targeted multi-cultural drivers’ population, the results of reaction time and jerk distributions could be used as inputs in simulation models which are developed for evaluating driver behavior and safety at signalized intersections in regions with multi-cultural driving population

Analysis of Stopping Sight Distance (SSD) Parameters: A Review Study

Stopping sight distance (SSD) is one of the important elements in geometric highway design, which relies on the two key parameters, i.e., vehicle braking characteristics and drivers' reaction time. Previous studies have shown higher discrepancies in the coefficients of the SSD parameters, and therefore, making it difficult for practitioners what values to be followed. Therefore, this review study aims to compare deceleration rates and PRT values in different situations that can be applied to geometric highway design. To this end, two electronic databases were searched and relevant articles that reported drivers' perception reaction time (PRT) or deceleration rates in different situations were identified and included in the review. The obtained results showed that deceleration rates of vehicles ranged from 0.49 m/s2to 8.76 m/s2with a total weighted average of 2.82 m/s2. On the other hand, PRT of drivers ranged from 0.48 seconds to 2.01 seconds, with a total weighted average of 1.21 seconds. The key factors that were assessed on deceleration rate of vehicles are surface condition; vehicle type; stimulus; and initial speed. Results of this study suggest that all these factors, except for initial speeds greater than 80 km/h, have a significant effect on deceleration rates of vehicles. The findings of this study could be used as inputs in geometric highway design calculations under different conditions.The Qatar-Japan Research Collaboration (QJRC) award [M-QJRC-2020-8] from Qatar University

Modelling speed behaviour in rural highways: Safety analysis of driving under adverse road-weather conditions

This study proposes a methodical approach to model desired speed distributions under different road-weather and traffic conditions followed by identification of road-weather conditions with potentially higher safety risks in rural divided highways located in extremely cold regions. Desired speed distributions encompassing unique combinations of adverse road-weather and traffic conditions are modelled as normal distributions characterized by their means and standard deviations formulated based on two principal statistical theorems and techniques i.e., Central Limit Theorem and Minimum Variance Unbiased Estimation. Combination of the precipitation conditions, road surface conditions, time of the day, temperature, traffic flow and the heavy vehicle percentage at the time of travel were considered in defining the combinations of road-weather and traffic conditions. The findings reveal that simultaneous occurrence of particular precipitation and pavement conditions significantly affect the characteristics of the desired speed distribution and potentially expose drivers to elevated safety risks. Jurisdictions experiencing extreme road-weather conditions may adapt the proposed methodology to assess speed behaviour under different road-weather conditions to establishing and deploying weather-responsive traffic management strategies such as variable speed limit to regulate speeding and improve traffic safety in winter

Driving simulation sickness and the sense of presence: Correlation and contributing factors

Driving simulators are useful and effective tools for conducting studies in the field of traffic safety. Simulation sickness (SS) and the sense of presence (SP) are two well-known factors that could affect the results of the driving simulator experiments. This study investigated the relationship between SP and SS in a medium-fidelity driving simulator. Additionally, the impact of the road environment (urban arterials or rural expressways) on these subscales was investigated. Data was collected by means of self-reported questionnaires, which were conducted after the participants have driven the simulation scenarios in a fixed-base medium-fidelity driving simulator. A total of 125 drivers participated in this study. Results showed that females reported significantly higher SS scores than males. An increasing trend in the SS was observed with the increase of age. Importantly, designing buildings that replicate a real-world environment could increase SP and decrease SS. Moreover, designing high quality and resolution scenarios could also increase SP, thus decreasing the severity of SS symptoms. The results of this study can help researchers using medium-fidelity driving simulators to know the influencing factors for each subscale of SP on SS. Adjustments in the driving simulator and scenario settings as well as additional training exercises for higher speed scenarios can be beneficial in reducing the severity of SS.The NPRP award [NPRP11S-1228-170143] from the Qatar National Research Fund (a member of Qatar Foundation). Open Access funding provided by the Qatar National Library

A study on the determinants of Ethiopian minibus taxi drivers' speeding behaviour: An application of the 'major theorists' model

Speeding is the most common road safety problem that results in many traffic accidents in Addis Ababa, Ethiopia. Minibus taxis substantially contribute to speed-related road traffic crashes in Addis Ababa. This study aimed to investigate minibus taxi drivers' speeding behaviour using the 'major theorists' model, an integrated framework drawn from five dominant motivational models. Participants were 218 Ethiopian male minibus taxi drivers in Addis Ababa. The study followed a three-step sequential procedures: 1. Development of a new instrument addressing the assumptions of the 'major theorists' model, and validation using Principal Component Analysis (PCA). 2. Exploration of associations between variables in the 'major theorist' model using a Pearson's correlation analysis. 3. Identification of statistically significant predictors of self-reported speeding via linear multiple regression analyses. It was found that self-efficacy to drive fast, weak speed enforcement, social pressure from relatives to drive fast, and behavioural intention to drive fast were significant predictors of self-reported speeding behaviour. These findings can be applied in awareness rising interventions for taxi driver to improve their speed limit compliance.The NPRP award [NPRP11S-1228-170143] from the Qatar National Research Fund (a member of Qatar Foundation)

Autonomous vehicles between anticipation and apprehension: Investigations through safety and security perceptions

Due to the ongoing enormous infrastructural developments and car ownership culture in Qatar, it could be one of those countries to introduce Autonomous Vehicles (AV) technology at the early stages. Therefore, this study surveyed a number of residents at the State of Qatar to improve our understandings of their perceptions regarding overall safety of AV (General_safety), safety due to the fact that AV could eliminate human errors (Human_errors), safety due to the interactions between Human-Driven Vehicles (HDV) and AV (HDV-AV_interactions), performance in harsh environmental conditions, security, comfort level, travel time, congestion and operational costs. In addition, the study uncovered the relationships of public perceptions towards AV and some other contextual factors with the willingness to adopt it in the future. To study these relations, we relied on a Structural Equation Modeling. Overall, the results showed that respondents had higher and positive perceptions regarding “General_safety” and “Human_errors”, however, they were more concerned about “HDV-AV_interactions” and its security. In addition, individuals’ preference to shift to AV in the future was positively correlated with their perception level of “General_safety”, “Human_errors”, Comfort and Travel_time. Regarding ethnicity of the respondents, non-Arabs reported higher concerns regarding AV security, compared to Arabs. Furthermore, interestingly the results revealed that individuals having higher knowledge about AV technology had more concerns on “General_safety” and “HDV-AV_interactions”, while they had positive perceptions that AV could eliminate human errors. The findings from this study are anticipated to allow AV manufacturers and other relevant authorities to enhance public confidence towards AV technology by targeting different sub-groups through particular safety or security awareness campaigns.The Qatar–Japan Research Collaboration Application Award [M-QJRC-2020-8] from Qatar University. Open Access funding provided by the Qatar National Library

Do detection-based warning strategies improve vehicle yielding behavior at uncontrolled midblock crosswalks?

Pedestrians being the most vulnerable road users account for a large proportion of injuries and fatalities from road traffic crashes. Pedestrians are involved in around one-third of the whole fatalities coming from the road traffic crashes in the state of Qatar. In areas with uncontrolled midblock crosswalks, it is very crucial to improve drivers’ alertness and yielding behavior. The objective of this driving simulator study is to investigate the impact of pedestrian detection strategies and pavement markings on driving behavior at high-speed uncontrolled crosswalks. To this end, an untreated condition (i.e. Control) was compared with three treatment conditions. The three treated conditions included two detection strategies, i.e., advance variable message sign (VMS) and LED lights, and road markings with pedestrian encircled. Each condition was tested with a yield/stop controlled marked crosswalk for two situations, i.e. with vs. without a pedestrian present. The experiment was conducted using the driving simulator at Qatar University. In total, 67 volunteers possessing a valid Qatari driving license participated in the study. Different analyses were conducted on vehicle-pedestrian interactions, driving speed, variations in acceleration/deceleration and lateral position. The results showed that both the LED and VMS conditions were helpful in increasing yielding rates up to 98.4 % and reducing the vehicle-pedestrian conflicts significantly. Furthermore, both treatments were effective in motivating drivers to reduce vehicle speed in advance. Considering the findings of this study, we recommend LED and VMS conditions as potentially effective solutions to improve safety at yield/stop controlled crosswalks.The NPRP award [NPRP 9-360-2-150] from the Qatar National Research Fund (a member of Qatar Foundation). Open Access funding provided by the Qatar National Library

Analysis of gap parameters for the estimation of single lane roundabouts' capacity in the State of Qatar

Entry capacity is an important parameter for evaluating the roundabout performance. In general, entry capacity is influenced by three gap parameters: critical gap, follow-up time and minimum headway of circulating vehicles. These gap parameters certainly are correlated with the driving behavior as well as the roundabout characteristics. In this paper, video records of two single roundabouts in the state of Qatar were used to estimate the gap parameters. In addition, the entry capacity of both roundabouts was estimated and compared through different methodologies. Results showed that the entry capacity is directly related with the inscribed circle diameter (ICD) until 400 vph of circulating flow. However, it is inversely related with ICD if the circulating flow exceeds 400 vph. Moreover, we found that the entry capacity has a negative relation with the gap parameters. Estimated entry capacities with the calibrated Highway Capacity Manual 6th Edition model (HCM, 2016) were significantly higher than estimated ones through the proposed approach by Qatar Highway Design Manual (QHDM, 2015). Interestingly, the entry capacity was underestimated in both approaches if default gap parameter values are used compared to the calibrated models using the observed gap parameters (36.7% less for HCM, and 19.4% less for QHDM). Thus, the utilization of realistic gap parameter values representing local traffic condition is essential for traffic planners to accurately estimate the entry capacity and accordingly ensure feasible design of different types of roundabouts

Aberrant driving behaviors as mediators in the relationship between driving anger patterns and crashes among taxi drivers: An investigation in a complex cultural context

Objective: Taxis have become an integrated component of Qatar’s urban transportation network due to their convenience, comfort, and flexibility. Qatar has seen an uptick in the demand for professional taxi drivers. Most Qatari taxi drivers come from developing countries with poor awareness of road safety; therefore, they regularly engage in aberrant driving behavior, leading to traffic violations and crashes. For taxi rides to be safer, it is essential to determine the association between driving aberration and road traffic crashes (RTCs), with an emphasis on the underlying factors that trigger these behaviors. Methods: To this end, we collected the data from taxi drivers relying on standard questionnaires, namely the Driving Anger Scale (DAS) and the Driver Behavior Questionnaire (DBQ), together with the real crash data of the same taxi drivers obtained from the police department. We relied on factor analysis to identify the main factors of these tools and then structural equation modeling to predict their causal relationship with RTCs. Results: The results indicated that the component of DAS, namely “illegal driving”, triggered all dimensions of aberrant driving behaviors, whereas hostile gestures had a positive correlation with lapses. In addition, the factor “error” was identified as a significant direct predictor, while the factor “illegal driving” was identified as a significant indirect predictor for RTCs. Regarding demographic characteristics, professional driving experience was found to be negatively associated with RTCs. Conclusion: Driving aberration mediated the impact of driving anger on RTCs. The findings from this study could help road safety practitioners and researchers better understand these relations. In addition, these results could also be very helpful for driving instructors to train taxi drivers in a way to cope with provoking situations.Open Access funding provided by the Qatar National Library. This study was made possible by the internal grant award [QUCG-CENG-21/22-2] from Qatar University