Driver perception of roadside configurations on two-lane rural roads: Effects on speed and lateral placement

Information density threshold of urban road traffic signs based on visual comfort

The content and density of traffic signs directly affect the operation of urban road traffic and drivers. To overcome the limitations of quantitative research on the density threshold of traffic signs on urban roads, a real vehicle experiment was conducted to record the psychological characteristics of drivers. Four psychological parameters of drivers-pupil area, fixation intensity, heart rate change rate, and heart rate variability-were explored. Subsequently, principal component analysis was used to present a new index, S, divided into 5 grade scales, to represent the driving visual comfort level. The information entropy theory was applied to quantify the amount of information on road traffic signs that are included in driving tests, and a regression relationship between the traffic sign information and comfort index S was established. The visual psychological load thresholds for different comfort levels were -2.289≤S < -1.526 for very comfortable, 1.526≤S < -0.763 for relatively comfortable, -0.763≤S ≤ 0.763 for comfortable, 0.763 Collapse

Key Words

• Amount of information
• Information density
• Real vehicle test
• Traffic sign
• Urban road
• Visual comfort

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Affiliation(s)

Hui Hu Nanchang Urban Planning & Design Institute Group Co., Ltd., Nanchang, 330038, China
Feng He Nanchang Urban Planning & Design Institute Group Co., Ltd., Nanchang, 330038, China
Yunwei Meng Chongqing Key Laboratory of Intelligent Integrated and Multidimensional Transportation System, Chongqing Jiaotong University, Chongqing, 400074, China
Youzhang Yang Nanchang Urban Planning & Design Institute Group Co., Ltd., Nanchang, 330038, China
Binbin Li Chongqing Key Laboratory of Intelligent Integrated and Multidimensional Transportation System, Chongqing Jiaotong University, Chongqing, 400074, China
Guangyan Qing China Merchants Roadway Information Technology (Chongqing) Co., Ltd., Chongqing, 400067, China

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Influence of continuous edge-line delineation on drivers' lateral positioning in curves: a gaze-steering approach

Recent research indicates that installing shoulders on rural roads for safety purposes causes drivers to steer further inside on right bends and thus exceed lane boundaries. The present simulator study examined whether continuous rather than broken edge-line delineation would help drivers to keep their vehicles within the lane. The results indicated that continuous delineation significantly impacts the drivers' gaze and steering trajectories. Drivers looked more towards the lane centre and shifted their steering trajectories accordingly. This was accompanied by a significant decrease in lane-departure frequency when driving on a 3.50-m lane but not on a 2.75-m lane. Overall, the findings provide evidence that continuous delineation influences steering control by altering the visual processes underlying trajectory planning. It is concluded that continuous edge-line delineation between lanes and shoulders may induce safer driver behaviour on right bends, which has potential implications for preventing run-off-road crashes and cyclist safety.Practitioner summary: This study examined how continuous and broken edge lines influence driving behaviour around bends with shoulders. With continuous delineation, drivers gazed and steered in the bend further from the edge line and thus had fewer lane departures. Continuous marking can therefore help prevent run-off-road crashes and improve cyclists' safety.

Research on left hard shoulder width of super multilane highway based on PTSU operation

Part-time shoulder use (PTSU) is a traffic strategy that temporarily uses the shoulder as a lane when necessary. Research has shown that, when a hard shoulder is required to set the traffic function, the left hard shoulder is preferable. Super multilane highways are usually equipped with left hard shoulders of sufficient width, but the wide cross-sectional characteristics make it difficult for vehicles to turn into the emergency parking lane to avoid a breakdown or accident in the lane, which is an ideal implementation object of PTSU. In this study, two virtual simulation scenarios for PTSU were created: one with the left hard shoulder open and used as a travel lane, and the other with the left hard shoulder closed and its original function restored. Vehicle driving data were collected through driving simulation experiments to reveal the influence of the left hard shoulder on vehicle handling stability. The optimal width of the left hard shoulder was determined by ANOVA and comparison of the mean and standard deviation. The purpose of this study was to quantify the effect of the width of the left hard shoulder on the driving stability of vehicles in the inside lane under PTSU and determine the ideal shoulder width by comparing the stability parameters of vehicles.

Effects of design consistency on run-off-road crashes: An application of a Random Parameters Negative Binomial Lindley model

Run-off-road crashes are one of the most common crash types, especially in rural roadway environments contributing significantly to fatalities and severe injuries. These crashes are complex and multi-dimensional events, and factors like road geometry, driver behaviour, traffic characteristics and roadside features contribute to their occurrence, separately or interactively. Sudden changes in road geometry, in particular, can influence driver behaviour, and therefore, in developing a micro-level crash risk model for run-off-road crashes, one of the challenges is incorporating the effects of driver behaviour (disaggregated information) that may arise from the variations in road geometry (aggregated information). This study aims to examine the interaction between road geometry and driver behaviour through a set of measures for design consistency on two-lane rural roads. Multiple data sources, including crash data for 2014-18, traffic data, probe speed data and roadway geometric data, for twenty-three highways in Queensland, Australia, have been fused for this study. Seventeen types of design consistency measures with regard to alignment consistency, operating speed consistency and driving dynamics are tested. A run-off-road crash risk model is estimated by employing the Random Parameters Negative Binomial Lindley regression framework, which accounts for excess zeros in the crash counts and captures the effects of unobserved heterogeneity in the parameter estimates. Results indicate that the geometric design consistency capturing the interaction between driver behaviour and operational factors better predicts run-off-road crashes along rural highways. In addition, roadside attributes like clear zone width, infrastructures, terrain, and roadway remoteness also contribute to run-off-road crashes. The findings of the study provide a comprehensive understanding of the influence of variations in roadway geometry on driver behaviour and run-off-road crashes along rural highways.

How do driving behavior and attitudes toward road safety vary between developed and developing countries? Evidence from Iran and the Netherlands

INTRODUCTION

The rates of road traffic injuries and fatalities in developing countries are significantly higher than in developed countries. This study examines the differences in driving behavior, road safety attitudes, and driving habits between a developed country (the Netherlands) and a developing country (Iran), which bear major differences in terms of crash involvement per population.

METHOD

In this context, this study assesses the statistical association of crash involvement with errors, lapses, aggressive driving incidents, and non-compliance with traffic rules, attitudes, and habits. Structural equation modeling was used to evaluate data obtained from 1,440 questionnaires (720 samples for each group).

RESULTS

The results revealed that more insecure attitudes toward traffic-regulation observance, negative driving habits, and risky behaviors, such as traffic rule violations act as influential factors of crash involvement. Iranian participants showed a greater likelihood to get involved in violations and driving habits with a higher level of risk. In addition, lower levels of safety attitudes toward traffic-regulation observance were observed. On the other hand, Dutch drivers were more likely to report lapses and errors. Dutch drivers also reported safer behavior in terms of unwillingness to engage in risky behaviors such as violations (speeding and no-overtaking). The structural equation models for crash involvement based on behaviors, attitudes, and driving habits were also evaluated for their accuracy and statistical fit using relevant indicators.

PRACTICAL APPLICATIONS

Finally, the findings of the present study point out the need for extensive research in some areas to foster policies that can effectively enhance safer driving.

A driving simulator study to evaluate the effects of different types of median separation on driving behavior on 2 + 1 roads

In recent years, several countries have started to introduce 2 + 1 roads into their road networks. Although some studies have recognized the great benefits of using 2 + 1 roads, few studies have investigated the effects of different design features of 2 + 1 roads on driver behavior and driving performance, including the type of median separation between opposing traffic flows. The overall aim of this driving simulator study is to determine whether different types of median separation on 2 + 1 roads affect driving behavior, and to provide new insights for designing more effective and safer 2 + 1 roads. A driving simulator study was carried out, and forty-six participants took part in the experiments. The scenario exactly reproduced an existing two-lane rural road in Poland where 2 + 1 sections are implemented; four different median separation types were tested: 1) double-line markings only; 2) reflective elements; 3) flexible guideposts; 4) cable barriers. The effects of the different types of median separation on driving behavior were statistically analyzed using data from 184 simulation tests. The results of the study suggest that the type of median separation significantly affects driving behavior on 2 + 1 roads. While the driving speeds on the passing lane did not differ significantly between the four configurations of the median separation, the lateral position of the passing vehicle on the additional lane was found to be significantly influenced by the type of separation, with a greater distance from the median recorded when the cable barriers were implemented. The potential of using driving simulation to test different solutions for 2 + 1 roads and select the most effective alternative in terms of safety and operation is demonstrated in this study. The results of this study can also be used to improve the behavioral models that can be implemented in the traffic micro-simulation of 2 + 1 road conditions.

Gaze and steering strategies while driving around bends with shoulders

The installation of shoulders on rural roads to create more forgiving roads encourages drivers to cut corners on right-hand bends, but the underlying mechanisms are poorly understood. Since eye movements and steering control are closely coupled, this study investigated how the presence of a shoulder influences drivers' gaze strategies. To this end, eighteen drivers negotiated right-hand bends with and without a shoulder on a simulated rural road. In the presence of a shoulder, participants modified their visual sampling of the road by directing their gaze further inside the bend. At the same time, their lane position was deviated inward throughout the bend and the vehicle spent more time out of the lane. These results suggest that the shoulder influences the visual processes involved in trajectory planning. Recommendations are made to encourage drivers to keep their eyes and vehicle in the driving lane when a shoulder is present.

Three-dimensional characterization and calculation of highway space visual perception

To quantify the impact of three-dimensional highway spatial characteristics on drivers' visual perception, this study analyzes the measurement points of highway spatial visual perception from the perspectives of spatial visual depression and spatial visual continuity based on spatial perception theory. Based on the hemispherical field of view, a spatial enclosure calculation method improved by "Distance/Height value" is proposed. A three-dimensional quantification model of the build-to-line ratio, including the vertical direction, was established using the relative relationship between the maximum section plane and the road area. Finally, a 3D real-scene model of the demonstration highway section was established, the proposed three-dimensional quantization method of visual perception of highway space was applied, and the road area landscape construction and promotion strategy is proposed based on the quantitative calculation results. The results show that: the overall landscape space of the highway section is undulating and that there is a lack of visual continuity. It is advisable to plant an appropriate amount of vegetation on the side of the road at 0 m-250 m and 500 m-700 m of the road section to reduce the fluctuation of its enclosure and enhance its spatial continuity. The improved quantitative results of the spatial enclosure degree and the three-dimensional build-to-line ratio can well characterize the spatial visual depression and the spatial visual continuity and can provide a basis and support for road space reorganization and the improvement of landscape construction.

Modeling driver's braking and steering behavior along horizontal curves of two-lane rural highways for ADAS applications

OBJECTIVE

Drivers continuously manipulate the vehicle's steering and pedals (throttle, brake) while driving. Inadequate or excessive manipulation leads to crashes, possibly leading to injuries. An Advanced Driving Assistance System (ADAS) can warn drivers of inadequate or excessive manipulation to avert risky situations. Such systems evolve continuously and need more road infrastructure inputs for better driving assistance. Rural highways showcased more fatalities than urban counterparts, with more road departure crashes along horizontal curves than straight sections. Hence, the present study explores drivers' braking and steering behavior along the horizontal curves of two-lane rural highways and proposes a suitable runoff risk model.

METHODS

Sixty-eight drivers participated in a driving simulator study, where they drove along fifty-two horizontal curves in free-flow conditions. Typical five brake and three steering measures found in past studies were evaluated. Based on data distribution of brake and steering measures, Tobit and mixed-effects multiple linear regression models were developed to understand the association of these measures with the approach speed and geometric parameters of horizontal curves. Further, a generalized linear mixed runoff (road departure) risk model with a logit link function was developed to identify the effective measures among all brake and steering variables.

RESULTS

The brake and steering measures were significantly associated with the approach speed and the geometric parameters such as curve radius, gradient, and turn type (left or right). Further, the runoff risk analysis revealed a significant effect of braking distance (BD) and standard deviation of steering wheel position (SDSWP). The interaction between BD and SDSWP was significant, suggesting that the runoff risk increased with SDSWP; however, it decreased with BD.

CONCLUSIONS

The runoff risk intensified with higher steering instability along horizontal curves, while it can be reduced with effective brake pedal usage. The study suggests better usage of brakes than steering before entering the curve. It potentially reduces the vehicle speed, thus ensuring more time to perceive the curve and help reduce the driver's steering instability. The models developed in this study can be used in the ADAS systems upon validation with the field observations.

Investigating the effects of travel lane configuration and lane width on traffic safety where powered-two-wheelers (PTWs) share with larger vehicles: A micro perspective

The design of travel lane configuration and lane width is crucial to traffic safety, especially in an urban mixed traffic environment where Powered-Two-Wheelers (PTWs) are prevalent and share the same roads with larger vehicles such as cars, buses, and trucks. However, there have been limited studies on the effects of the design of travel lane configuration and lane width on safety in such a mixed traffic environment. It's true the above-mentioned research question can be evaluated simply in terms of the number of crashes. However, doing so not only requires a few years of crash and traffic data, but limited insight can be gained in terms of how driver and rider behaviours are affected, and this has implications for further improvement in road safety. This study examines the changes in driving/riding behaviours and surrogate events before and after the adjustments of travel lane configuration and lane width by proposing a micro perspective approach as a complement to conventional studies. A before-and-after site-based investigation was conducted at two study sites which had opposite adjustments for travel lane configuration and lane widths: at one site the number of lanes was reduced, thereby widening the lane width in the outer lane on one road section, and at the second site the number of lanes was increased, thereby narrowing lane width in the outer lane on the other road section. The results showed that an increase in lane width resulted in a considerable increase in the number of speeding events as well as unsafe driving/riding behaviours and surrogate events related to lane splitting, lane sharing, and overtaking.

The effect of listening to Iranian pop and classical music, on mental and physiological drowsiness

Driver's drowsiness is one of the high-risk road behaviors that quadruples the risk of road accidents. Measures to deal with drowsiness during driving include listening to music. The present study investigates the effect of two types of music, namely Iranian high-tempo pop and classical music, on mental and physiological drowsiness during driving. Twelve male students at Tehran University of Medical Sciences within the normal range of the Epworth Drowsiness Scale (ESS) participated in this study. Two types of music (classical and pop) were assessed on two separate days with an interval of one week. The mental aspect of drowsiness was evaluated using the Karolinska Sleepiness Scale (KSS), the physiological aspect by monitoring the EEG and heart rate, and the functional aspect through the mean and standard deviation of speed and the Standard Deviation of Lateral Position (SDLP) in a driving simulator. The results showed that the brain waves (four algorithms (1) (θ + α)/β, (2) α/β, (3) (θ + α)/(α + β) and (4) θ/β), the KSS score, SDLP and standard deviation of speed all decrease while the mean heart rate increases when listening to music during driving compared to driving without music. No significant difference was observed in the mean speed when exposed to music. Moreover, no difference was observed between the effect of the two music styles, i.e. Iranian classical and pop music. Listening to Iranian classical and pop music while driving improves the driver's performance and reduces drowsiness. The present study showed that higher tempo music during driving can reduce drowsiness and change physiological responses and driving performance.

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.

Optical pavement treatments and their impact on speed and lateral position at transition zones: A driving simulator study

Transition zones are a road section where posted speed drops from higher to lower limits. Due to the sudden changes in posted speed limits and road environment, drivers usually do not adapt to the posted speed limits and underestimate their traveling speed. Previous studies have highlighted that crash rates are usually higher in these sections. This study aims at improving the safety at transition zones by introducing perceptual measures that are tested using a driving simulator. The proposed measures are speed limit pavement markings with a gradual increase of brightness and/or size that were placed at transition zones in simulation scenarios replicating the real-world environment of the Doha Expressway in Qatar. These innovative measures aim to produce the impression of increased speed that could stimulate drivers to better adapt speed limits. The driving behavior of 81 drivers possessing a valid Qatari driving license was recorded with a driving simulator interfaced with STISIM Drive® 3. Results showed that pavement markings combining size and brightness manipulations were the most effective treatment, keeping drivers' traveling speed significantly below the traveling speed recorded in the untreated control condition. In this regard, the maximum mean speed reductions of 5.3 km/h and 4.6 km/h were observed for this treatment at the first transition (120 to 100 km/h) and second transition (100 to 80 km/h) zones, respectively. Regarding the variations in drivers' lateral position, the results showed that the proposed pavement markings did not negatively influence drivers' lateral control on the road as the maximum observed standard deviation of lateral position was around 0.065 m. This study shows that the proposed pavement markings are recommended for improving the speed adaptation of drivers in the transition zones.

A novel approach to set driving simulator experiments based on traffic crash data

Several studies have often cited crash occurrences as a motivation to perform a driving simulator experiment and test driver behavior to understand their causal relations. However, decisions regarding the simulated scenario and participants' requirements do not often rely directly on traffic crash data. To fill the gap between simulation and real data, we have proposed a new framework based on Clustering Analysis (K-medoids) to support the definition of driving simulator experiments when the purpose is to investigate the driver behavior under real risky road conditions to improve road safety. The suggested approach was tested with data of three years of police records regarding loss-of-control crashes and information on three Brazilian rural highways' geometry and traffic volume. The results showed the good suitability of the method to compile the data's diversity into four clusters, representing and summarizing the crashes' main characteristics in the region of study. Drivers' attributes (age and gender) were initially intended to integrate the clustering analysis; however, due to the sample's homogeneity of these characteristics, they did not contribute to the cluster definition. Hence, they were used simply to identify the target population for all scenarios. Therefore, we concluded that driving simulator experiments could benefit from the new approach since it identifies scenarios characterized by many variables connected to real risky situations and orients participants' recruitment leading to efficient safety analysis.

Driving simulators to evaluate road geometric design effects on driver behaviour: A systematic review

Several factors can influence driver behaviour, and road geometry is one of them. A better understanding of driver-roadway interaction can enhance road design to create a safer traffic system. In this context, driving simulators are powerful tools that combine convenience and effectiveness in identifying drivers' responses to different geometry factors. In this paper, a systematic review following a Prisma guideline was conducted on driving simulator studies that examined the effects of road geometry on driver behaviour to reveal the current procedures adopted in this field and their main findings. A systematic search of eleven databases was performed covering six years of research results. Inclusion of relevant studies focused on horizontal curves, a topic identified as the most cited, extended this period. The results revealed significant heterogeneity in relation to the measured variables and deficiencies when reporting the experiment, which prevented a meta-analysis of the studies' outcomes. Despite this, a discussion of the potential of driving simulators to contribute to several road safety research gaps is presented. In addition, problems of a lack of standardisation in the performance of the experiments were detected, potentially influencing the findings of the studies. However, the results also suggest that experiments that followed good experimental practices observed effects on driver performances not detected by other studies.

A Novel CRITIC-Fuzzy FUCOM-DEA-Fuzzy MARCOS Model for Safety Evaluation of Road Sections Based on Geometric Parameters of Road

Trends of globalization very often cause the emergence of phenomena that asymmetrically affect the overall sustainability of the transport system. In order to predict certain situations and potentially be able to manage the transport system, it is necessary to manage risk situations and traffic safety in a timely manner. This study has conducted an investigation which implies defining the level of safety of a total of nine sections of two-lane roads. The main aim of the paper is to create a new multiphase model consisting of CRITIC (The CRiteria Importance Through Intercriteria Correlation), Fuzzy FUCOM (Full Consistency Method), DEA (Data Envelopment Analysis), and Fuzzy MARCOS (Measurement Alternatives and Ranking according to the COmpromise Solution) methods for determining the level of traffic safety on road sections under the conditions of uncertainty. In order for the created model to be adequately applied, eight parameters were created, and they were classified through four inputs and four outputs. To calculate the significance of the inputs, the CRITIC method based on the symmetric correlation matrix was used, and taking into account the nature of the outputs, the Fuzzy FUCOM method based on averaged values using the fuzzy Bonferroni Mean (BM) operator was applied to determine their weights. To determine the degree of safety, the DEA model was created. After that, the Fuzzy MARCOS method was used in order to determine the final ranking of the remaining five sections of the road network. Finally, the verification of results was performed through three phases of Sensitivity Analysis (SA).

Effectiveness of yellow color guardrail belt at freeway exits

If the information on freeway exits is not effective or driver vigilance is not adequate, the driver may not be able to obtain the information in time, resulting in missing the exit or making a forcible lane-change that could cause an accident. To allow the driver to obtain sufficient exit information in time and get off the freeway safely, this study proposes the creation of a guardrail painted with a yellow color and located prior to the exit. The yellow color guardrail belt (YCB) aims at informing the drivers that there is an exit ahead and to pay attention to the exit information, reminding them to adjust vehicle state and driving behavior in time. A driving simulator experiment with two different scenarios (YCB scenario and baseline scenario with no YCB) were used to explore the effectiveness of the YCB. Data on eye movement, electroencephalograph, and driving behavior of the participants were obtained. The results showed that compared with the baseline scenario, in the YCB scenario, the fixation points were mainly distributed in front of the road and the fixation duration on the guide signs was relatively longer; the EEG ratio (θ + α) / β was smaller; the driver decelerated more smoothly; and the steering wheel angle was smaller. In addition, the statistical analysis showed that there were significant differences in the fixation duration, the EEG ratio (θ + α) / β, and steering wheel angle between the two scenarios. This indicated that participants' vigilance in the YCB scenario was significantly improved, where the participants paid more attention to the guide signs and had better control of the vehicle. This study recommends a new device for reminding drivers to pay attention to freeway exits, which would greatly stimulate driver's sense of space on the exit and improve traffic safety on freeways.

Human-like driving behaviour emerges from a risk-based driver model

Current driving behaviour models are designed for specific scenarios, such as curve driving, obstacle avoidance, car-following, or overtaking. However, humans can drive in diverse scenarios. Can we find an underlying principle from which driving behaviour in different scenarios emerges? We propose the Driver’s Risk Field (DRF), a two-dimensional field that represents the driver’s belief about the probability of an event occurring. The DRF, when multiplied with the consequence of the event, provides an estimate of the driver’s perceived risk. Through human-in-the-loop and computer simulations, we show that human-like driving behaviour emerges when the DRF is coupled to a controller that maintains the perceived risk below a threshold-level. The DRF model predictions concur with driving behaviour reported in literature for seven different scenarios (curve radii, lane widths, obstacle avoidance, roadside furniture, car-following, overtaking, oncoming traffic). We conclude that our generalizable DRF model is scientifically satisfying and has applications in automated vehicles.

Most driver models were designed for specific scenario. Here, the authors developed a driver behaviour model that can be applied to multiple scenarios and show that human-like driving behaviour emerges when the Driver’s Risk Field is coupled to a controller that maintains the perceived risk below a threshold level.

Cycling on the edge: the effects of edge lines, slanted kerbstones, shoulder, and edge strips on cycling behaviour of cyclists older than 50 years

To prevent single-bicycle crashes, this study is the first to evaluate effects of slanted kerbstones, edge lines, shoulder strips, and edge strips on cycling behaviour of cyclists ≥50 years. In Experiment 1, 32 participants cycled on a control path and paths with edge lines, slanted kerbstones, and three types of 0.5 m wide shoulder strips (with grey artificial grass, green artificial grass, or concrete street-print). In Experiment 2, 30 participants cycled a different route including a control path and paths with edge lines or 0.3 m white edge strips. Cyclists rode closer to the main cycle path's edge in the shoulder strips conditions, although the presence of these strips resulted in a larger total distance to the verge compared to the control condition. Furthermore, cyclists cycled further from the verge in the edge strip condition than the control condition. Safety implications of the shoulder and edge strips are considered to be positive. Practitioner Summary: Older cyclists have a high risk for single-bicycle crashes (e.g. riding into the verge). In two experiments, cyclists ≥50 years cycled a route where different treatments were applied on a cycle path. Shoulder and edge strip treatments were related to more efficient path use and safer distances from the verge. Abbreviations: AGS: artificial grass strip; CL: control location; CSS: concrete street-print strip; ELC: edge line continuous; ELI: edge line intermittent; LP: lateral position; SDLP: standard deviation of the lateral position; SK: slanted kerbstones; WCES: white chippings edge strip.

An Exploratory Study of Users’ Preference for Different Planting Combinations along Rural Greenways

The literature highlights the importance of vegetation to enhance the ecological and visual qualities of streets and paths; however, when studies specifically focus on rural greenways they do not consider users’ assessments of the planting design. This exploratory study aims to contribute to this issue. It is hypothesized that planting combinations characterized by greater variety and aesthetic flow may be more preferred and restorative. To this end, four virtual scenarios simulating bikers moving along a greenway at 25 km/h were created to find out the following: first, what kind of planting combination is the most preferred, and second, which planting combination is perceived as the most restorative by bicycle riders. To assess the experience, subjects were administered a questionnaire made up of: (i) the Perceived Restorativeness Scale-11 with additional items to assess compatibility, familiarity, and preference; (ii) a list of physical and aesthetic attributes; and (iii) information on bicycle use. The results show that participants’ preferences were affected by the perception of the scenario’s restorative value, which was not given exclusively by the degree of naturalness, but by the opportunity the greenway offered to engage in social/physical activities. This study shows that preference and restorativeness are not a “simple” matter of quantity of vegetation, but of quality instead, i.e., planting variety. Designers have to consider that the restorative value of greenways is related to the opportunities they offer to engage in physical/social activities.

Differences in the Gaze Behaviours of Pedestrians Navigating between Regular and Irregular Road Patterns

While a road pattern influences wayfinding and navigation, its influence on the gaze behaviours of navigating pedestrians is not well documented. In this study, we compared gaze behaviour differences between regular and irregular road patterns using eye-tracking technology. Twenty-one participants performed orientation (ORI) and shortest route selection (SRS) tasks with both road patterns. We used accuracy of answers and response time to estimate overall performance and time to first fixation duration, average fixation duration, fixation count and fixation duration to estimate gaze behaviour. The results showed that participants performed better with better accuracy of answers using irregular road patterns. For both tasks and both road patterns, the Label areas of interest (AOIs) (including shops and signs) received quicker or greater attention. The road patterns influenced gaze behaviour for both Road AOIs and Label AOIs but exhibited a greater influence on Road AOIs in both tasks. In summary, for orientation and route selection, users are more likely to rely on labels, and roads with irregular patterns are important. These findings may serve as the anchor point for determining how people’s gaze behaviours differ depending on road pattern and indicate that labels and unique road patterns should be highlighted for better wayfinding and navigation.

A driving simulation study to examine the impact of available sight distance on driver behavior along rural highways

The available sight distance (ASD) is the maximum length of the roadway ahead visible to the driver. It is a fundamental factor in road geometry principles and is used by road designers to ensure safe driving conditions. However, designers do not know how a specific ASD may affect the longitudinal and transversal behavior of drivers engaged in negotiating curves. This paper focuses on analyzing driver longitudinal behavior along rural highways curves with limited visibility. A number of virtual sight condition scenarios were recreated and tested in the driving simulator. Three tracks were designed with various combinations of radii and sight obstructions (a continuous wall) along the roadside located at various offsets from the lane centerline, combinations which resulted with a minimum ASD of 56.6 m. Roadside factors capable of influencing the risk perception of drivers (e.g., traffic barriers, posted speed limit signs, vegetation) were all excluded from the simulations. Results indicate that speed and trajectory dispersion from the lane centerline depend linearly on ASD in the investigated range of curve radii (from 120 to 430 m). In general, when ASD increases, so does speed and the trajectories tend to be less dispersed around the lane centerline. As a result, in safety terms, any variation in ASD will have the polar opposite effect on safety related parameters. Furthermore, different curves with similar ASD values resulted in different speed and lateral control behaviors. Analysis from ANOVA support the same findings; in addition, radius, curve direction, and distance from trajectory to sight obstruction have been identified as significant independent parameters. Road designers should adjust the ASD and these parameters when seeking to encourage drivers to adopt appropriate behaviors. To optimize safe driving conditions, ASD should be designed so that it is slightly greater than the required sight distance, since excessive ASD values may encourage drivers to drive at inappropriate speeds.

Examining vehicle operating speeds on rural two-lane curves using naturalistic driving data

Horizontal curves have been shown to exhibit crash rates significantly higher than comparable tangent segments. Extensive research has investigated the causes of crashes on horizontal curves, particularly the curve navigation process and driver speed selection. Research in this area has generally been limited by the nature of the data, which is often inhibited by practical constraints as to the number of locations and drivers that can be observed. This study overcomes these hurdles through the use of naturalistic driving data, providing insights on how drivers navigate and react to curves on rural two-lane highways. Nearly 10,000 vehicle traces were collected from 202 drivers on 219 horizontal curves as a part of this study. All driving traces were collected on rural two-lane highways with prevailing posted speed limits of 45 mph or 55 mph, as well as a diverse range of curve advisory speeds. Regression models are estimated via generalized estimating equations to discern those factors affecting mean speeds on curves. A log-linear relationship was found between curve radius and mean vehicle speed, with speeds relatively stable on radii of 900-1000 ft. or more, decreasing more rapidly as radii decreased below this range. Drivers were found to reduce speeds when curve advisories were present, but the magnitude of these reductions was much less than suggested by the advisory signs. Speeds were significantly lower when a W1-6 curve arrow sign was present adjusting for the curve radius. There were also some differences in speeds based on driver age and gender. Ultimately, this paper provides insights into driver curve navigation and demonstrates the potential of high-fidelity naturalistic driving data to assess speed management and geometric design on horizontal curves.

Steering Control in a Low-Cost Driving Simulator: A Case for the Role of Virtual Vehicle Cab

OBJECTIVE

The aim of this study was to investigate steering control in a low-cost driving simulator with and without a virtual vehicle cab.

BACKGROUND

In low-cost simulators, the lack of a vehicle cab denies driver access to vehicle width, which could affect steering control, insofar as locomotor adjustments are known to be based on action-scaled visual judgments of the environment.

METHOD

Two experiments were conducted in which steering control with and without a virtual vehicle cab was investigated in a within-subject design, using cornering and straight-lane-keeping tasks.

RESULTS

Driving around curves without vehicle cab information made drivers deviate more from the lane center toward the inner edge in right (virtual cab = 4 ± 19 cm; no cab = 42 ± 28 cm; at the apex of the curve, p < .001) but not in left curves. More lateral deviation from the lane center toward the edge line was also found in driving without the virtual cab on straight roads (virtual cab = 21 ± 28 cm; no cab = 36 ± 27 cm; p < .001), whereas driving stability and presence ratings were not affected. In both experiments, the greater lateral deviation in the no-cab condition led to significantly more time driving off the lane.

CONCLUSION

The findings strongly suggest that without cab information, participants underestimate the distance to the right edge of the car (in contrast to the left edge) and thus vehicle width. This produces considerable differences in the steering trajectory.

APPLICATION

Providing a virtual vehicle cab must be encouraged for more effectively capturing drivers' steering control in low-cost simulators.

Impact of roadway geometric features on crash severity on rural two-lane highways

This study examines the impact of a wide range of roadway geometric features on the severity outcomes of crashes occurred on rural two-lane highways. We argue that crash data have a hierarchical structure which needs to be addressed in modeling procedure. Moreover, most of previous studies ignored the impact of geometric features on crash types when developing crash severity models. We hypothesis that geometric features are more likely to determine crash type, and crash type together with other occupant, environmental and vehicle characteristics determine crash severity outcome. This paper presents an application of multilevel models to successfully capture both hierarchical structure of crash data and indirect impact of geometric features on crash severity. Using data collected in Illinois from 2007 to 2009, multilevel ordered logit model is developed to quantify the impact of geometric features and environmental conditions on crash severity outcome. Analysis results revealed that there is a significant variation in severity outcomes of crashes occurred across segments which verifies the presence of hierarchical structure. Lower risk of severe crashes is found to be associated with the presence of 10-ft lane and/or narrow shoulders, lower roadside hazard rate, higher driveway density, longer barrier length, and shorter barrier offset. The developed multilevel model offers greater consistency with data generating mechanism and can be utilized to evaluate safety effects of geometric design improvement projects.

Evaluating the effect of lane width and roadside configurations on speed, lateral position and likelihood of comfortable overtaking in exclusive motorcycle lane

Construction of exclusive motorcycle lanes is one of the measures to reduce motorcycle fatalities. Previous studies highlighted the risk of crashes with roadside objects and the tendency of motorcyclists to ride with excessive speed on exclusive motorcycle lanes. However, the risk of same-direction crashes on exclusive motorcycle lanes was not explored in much detail, especially on the impact of lane geometry and roadside configurations. This study used naturalistic riding data to determine the effects of lane width and roadside configurations on overtaking speed, lateral position and likelihood of comfortable overtaking on tangential sections of an exclusive motorcycle lane. Twenty-nine recruited motorcyclists rode the instrumented motorcycles along a 20km stretch of an exclusive motorcycle lane along a major urban road. Results revealed that both the roadside configurations and lane width significantly affect the participants' lateral position, while the roadside configurations only affects the overtaking speed. Participants' overtaking speeds and the front motorcycles' lateral position contribute significantly to the likelihood of comfortable overtaking in exclusive motorcycle lanes. The findings highlight the importance of micro-level behavior indicators in improving the design and overall safety of the exclusive motorcycle facility.

Crashes and near-crashes on horizontal curves along rural two-lane highways: Analysis of naturalistic driving data

INTRODUCTION

Prior research has shown the probability of a crash occurring on horizontal curves to be significantly higher than on similar tangent segments, and a disproportionally higher number of curve-related crashes occurred in rural areas. Challenges arise when analyzing the safety of horizontal curves due to imprecision in integrating information as to the temporal and spatial characteristics of each crash with specific curves.

METHODS

The second Strategic Highway Research Program(SHRP 2) conducted a large-scale naturalistic driving study (NDS),which provides a unique opportunity to better understand the contributing factors leading to crash or near-crash events. This study utilizes high-resolution behavioral data from the NDS to identify factors associated with 108 safety critical events (i.e., crashes or near-crashes) on rural two-lane curves. A case-control approach is utilized wherein these events are compared to 216 normal, baseline-driving events. The variables examined in this study include driver demographic characteristics, details of the traffic environment and roadway geometry, as well as driver behaviors such as in-vehicle distractions.

RESULTS

Logistic regression models are estimated to discern those factors affecting the likelihood of a driver being crash-involved. These factors include high-risk behaviors, such as speeding and visual distractions, as well as curve design elements and other roadway characteristics such as pavement surface conditions.

CONCLUSIONS

This paper successfully integrated driver behavior, vehicle characteristics, and roadway environments into the same model. Logistic regression model was found to be an effective way to investigate crash risks using naturalistic driving data.

PRACTICAL APPLICATIONS

This paper revealed a number of contributing factors to crashes on rural two-lane curves, which has important implications in traffic safety policy and curve geometry design. This paper also discussed limitations and lessons learned from working with the SHRP 2 NDS data. It will benefit future researchers who work with similar type of data.

The effects of lane width, shoulder width, and road cross-sectional reallocation on drivers' behavioral adaptations

Previous research has shown that lane-width reduction makes drivers operate vehicles closer to the center of the road whereas hard-shoulder widening induces a position farther away from the road's center. The goal of the present driving-simulator study was twofold. First, it was aimed at further investigating the respective effects of lane and shoulder width on in-lane positioning strategies, by examining vehicle distance from the center of the lane. The second aim was to assess the impact on safety of three possible cross-sectional reallocations of the width of the road (i.e., three lane-width reductions with concomitant shoulder widening at a fixed cross-sectional width) as compared to a control road. The results confirmed that lane-width reduction made participants drive closer to the road's center. However, in-lane position was affected differently by lane narrowing, depending on the traffic situation. In the absence of oncoming traffic, lane narrowing gave rise to significant shifts in the car's distance from the lane's center toward the edge line, whereas this distance remained similar across lane widths during traffic periods. When the shoulders were at least 0.50m wide, participants drove farther away from both the road center and the lane center. Road reallocation operations resulted in vehicles positioned farther away from the edge of the road and less swerving behavior, without generating higher driving speeds. Finally, it is argued that road-space reallocation may serve as a good low-cost tool for providing a recovery area for steering errors, without impairing drivers' behavior.

The effect of pavement markings on driving behaviour in curves: a simulator study

This study investigates the effect of two pavement markings (transverse rumble strips (TRS) and a backward pointing herringbone pattern (HP)) on speed and lateral control in and nearby curves. Two real-world curves with strong indications of a safety problem were replicated as realistic as possible in the simulator. Results show that both speed and lateral control differ between the curves. These behavioural differences are probably due to curve-related dissimilarities with respect to geometric alignment, cross-sectional design and speed limit. TRS and HP both influenced mean speed and mean acceleration/deceleration but not lateral control. TRS generated an earlier and more stable speed reduction than HP which induced significant speed reductions along the curve. The TRS gives drivers more time to generate the right expectations about the upcoming curve. When accidents occur primarily near the curve entry, TRS is recommended. The HP has the potential to reduce accidents at the curve end. Practitioner Summary: Two pavement markings (transversal rumble strips and HP) nearby dangerous curves were investigated in the driving simulator. TRS generated an earlier and more stable speed reduction than HP which induced speed reductions along the curve. The TRS gives drivers more time to generate right expectations about the upcoming curve.

Interaction driver-bicyclist on rural roads: Effects of cross-sections and road geometric elements

The interaction of motorists and bicyclists, particularly during passing maneuvers, is cited as one of the primary causes of bicyclist fatalities. This paper reports the results of a driving simulator study, which sought to analyze the effects that three cross-section configurations of a two-lane rural road and four geometric elements of the road have on driver behavior, during the interaction with a cyclist. A two-lane rural road, about 11km long, was designed and implemented in an advanced-interactive driving simulator. Three different cross-sections (all with same width, but with and without a bicycle lane and for different widths of bicycle lane) were tested. Forty participants carried out three driving sessions (one for each road alignment with different cross-section) and were exposed to the condition of bicycle traffic along four geometric elements of the alignment (2 tangents with different lengths, right curve and left curve). The driving simulator experiments were designed in such a way that, along the sections where the driver-cyclist interactions occurred, the oncoming traffic was absent. Overall, 468 speed profiles and 468 lateral position profiles were plotted to obtain the descriptive variables of the driver behavior during the interaction with the cyclist. The influences of cross-sections, geometric elements and bicycle traffic conditions on driver behavior were evaluated by a multivariate variance analysis. The presence of the cyclist determined different levels of influence on driver's trajectory for the three cross-sections. A wider bicycle lane ensured a higher later clearance distance between driver and cyclist, allowing safer overtaking maneuver. The interferences of the cyclist on driver's behavior depended on the geometric elements. On tangents, the lowest lateral clearances were recorded and no speed reduction was observed, compared to the cyclist absence condition. On the left curve, the higher lateral clearance was recorded, due to the concordant tendencies of the driver to move away from the cyclist and to cut the curve. This determined an excessive and risky displacement of the vehicle to the opposing lane, whose criticality was also emphasized by the high speed adopted by the driver. On the right curve, the lateral clearance was higher than that recorded on the tangents, probably due to the necessity of the driver to perform the demanding maneuver of entering in the right curve, which also determined a speed reduction compared to the cyclist absence condition. The obtained results provide suggestions for the most efficient cross-section reorganization of existing two-lane rural roads in order to improve the road safety.

Risk in our midst: Centrelines, perceived risk, and speed choice

The idea that drivers' perceptions of risk affect their decisions and choices, particularly as regards their speed, is at the heart of many years of our education, engineering, and enforcement strategies to improve road safety. Our previous research has shown that horizontal curvature, road width, vertical curvature and separation from on-coming traffic are principal determinants to perceptions of risk on rural roads. The present study examined the relationship between drivers' perceptions of risk and the speeds they choose to drive. Participants drove high definition videos of familiar rural roads in a driving simulator and a smaller group of participants drove the same roads in a university fleet vehicle similar to the one used in the simulator. The results showed that double yellow and wide centreline markings were associated with lower speed choices and higher perceptions of risk, an effect magnified under high traffic conditions. Similarly, in both the simulator and on the roads, driving on narrow roads was associated with significantly lower speeds and increased risk ratings, while wider roads showed a small but significant increase in speeds as compared to standard width control roads. Finally, a range of other road and traffic conditions such as one-lane bridges, level crossings, police cars, and crash area warning signs were also found to be associated with lower speed choices and higher risk perceptions.

Evaluating the safety risk of roadside features for rural two-lane roads using reliability analysis

The severity of roadway departure crashes mainly depends on the roadside features, including the sideslope, fixed-object density, offset from fixed objects, and shoulder width. Common engineering countermeasures to improve roadside safety include: cross section improvements, hazard removal or modification, and delineation. It is not always feasible to maintain an object-free and smooth roadside clear zone as recommended in design guidelines. Currently, clear zone width and sideslope are used to determine roadside hazard ratings (RHRs) to quantify the roadside safety of rural two-lane roadways on a seven-point pictorial scale. Since these two variables are continuous and can be treated as random, probabilistic analysis can be applied as an alternative method to address existing uncertainties. Specifically, using reliability analysis, it is possible to quantify roadside safety levels by treating the clear zone width and sideslope as two continuous, rather than discrete, variables. The objective of this manuscript is to present a new approach for defining the reliability index for measuring roadside safety on rural two-lane roads. To evaluate the proposed approach, we gathered five years (2009-2013) of Illinois run-off-road (ROR) crash data and identified the roadside features (i.e., clear zone widths and sideslopes) of 4500 300ft roadway segments. Based on the obtained results, we confirm that reliability indices can serve as indicators to gauge safety levels, such that the greater the reliability index value, the lower the ROR crash rate.

Effects of safety measures on driver's speed behavior at pedestrian crossings

This paper reports the results of a multi-factorial experiment that was aimed at the following: (a) analyzing driver's speed behavior while approaching zebra crossings under different conditions of vehicle-pedestrian interaction and with respect to several safety measures and (b) comparing safety measures and identifying the most effective treatment for zebra crossings. Three safety countermeasures at pedestrian crossings (curb extensions, parking restrictions and advanced yield markings) and the condition of no treatment (baseline condition) were designed on a two-lane urban road and implemented in an advanced driving simulator. Several conditions of vehicle-pedestrian interaction (in terms of the time left for the vehicle to get to the zebra crossing at the moment the pedestrian starts the crossing) were also simulated. Forty-two drivers completed the driving in the simulator. Based on the recorded speed data, two analyses were performed. The first analysis, which focused on the mean speed profiles, revealed that the driver's speed behavior was affected by conditions of vehicle-pedestrian interaction and was fully consistent with previous findings in the literature and with the Threat Avoidance Model developed by Fuller. Further analysis was based on variables that were obtained from the speed profiles of drivers (the speed at the beginning of the deceleration phase, the distance from the zebra crossing where the deceleration began, the minimum speed value reached during the deceleration, the distance from the pedestrian crossing where the braking phase ended and the average deceleration rate). Multivariate variance analysis (MANOVA) revealed that there was a significant main effect for safety measures and for pedestrian conditions (the presence and absence of a pedestrian). The results identified that the curb extension was the countermeasure that induces the most appropriate driver's speed behavior while approaching the zebra crossing. This conclusion was also confirmed by outcomes of the questionnaire on the countermeasure's effectiveness. More than 80% of the drivers perceived that the curb extensions were effective, which indicates that when this countermeasure was present, the drivers were more willing to yield and that the visibility of the pedestrian crossing was better. For this countermeasure, the lowest number of interactions in which the drivers did not yield to a pedestrian was also recorded.

Effects of fog, driver experience and gender on driving behavior on S-curved road segments

Driving on curved roads has been recognized as a significant safety issue for many years. However, driver behavior and the interactions among variables that affect driver performance on curves is complicated and not well understood. Previous studies have investigated various factors that influence driver performance on right- or left-turn curves, but have paid little attention to the effects of foggy weather, driver experience and gender on driver performance on complex curves. A driving simulator experiment was conducted in this study to evaluate the relationships between driving behavior on a continuous S-curve and foggy weather, driver experience and gender. The process of negotiating a curve was divided into three stages consisting of a straight segment, the transition from the straight segment to the S-curve and the S-curve. The experimental results indicated that drivers tended to drive more cautiously in heavy fog, but the driving risk was still increased, especially in the transition stage from the straight segment to the S-curve. The non-professional (NP) drivers were less sensitive to the impending change in the road geometry, and less skilled in both longitudinal and lateral vehicle control than the professional drivers. The NP female drivers in particular were found to be the most vulnerable group in S-curve driving.

Experimental research on safety impacts of the inside shoulder based on driving simulation

Statistical data shows that single-vehicle crashes account for half of all traffic crashes on expressways in China, and previous research has indicated that main contributing factors were related to whether and how the inside shoulder was paved. The inside shoulder provides space for drivers to make evasive maneuvers and accommodate driver errors. However, lower-cost construction solutions in China have resulted in the design of numerous urban expressway segments that lack inside shoulders. This paper has two objectives. The first is to reveal the safety impacts of inside shoulders on urban expressways by driving simulator experiment. The second objective is to propose optimal range and recommended value of inside shoulder width for designing inside shoulders of urban expressways. The empirical data, including subjects' eye movement data, heart rate (HR) and the lateral position of vehicles, were collected in a driving simulator. The data were analyzed to evaluate the safety impacts of the inside shoulder. The results have revealed that the inside shoulder has an impact on drivers' visual perception, behaviors, and psychology; in particular, it has a significant effect on vehicle operations. In addition, this paper recommends the desired and optimal inside shoulder widths for eight-lane, two-way divided expressways.

Mixed logit model-based driver injury severity investigations in single- and multi-vehicle crashes on rural two-lane highways

Crashes occurring on rural two-lane highways are more likely to result in severe driver incapacitating injuries and fatalities. In this study, mixed logit models are developed to analyze driver injury severities in single-vehicle (SV) and multi-vehicle (MV) crashes on rural two-lane highways in New Mexico from 2010 to 2011. A series of significant contributing factors in terms of driver behavior, weather conditions, environmental characteristics, roadway geometric features and traffic compositions, are identified and their impacts on injury severities are quantified for these two types of crashes, respectively. Elasticity analyses and transferability tests were conducted to better understand the models' specification and generality. The research findings indicate that there are significant differences in causal attributes determining driver injury severities between SV and MV crashes. For example, more severe driver injuries and fatalities can be observed in MV crashes when motorcycles or trucks are involved. Dark lighting conditions and dusty weather conditions are found to significantly increase MV crash injury severities. However, SV crashes demonstrate different characteristics influencing driver injury severities. For example, the probability of having severe injury outcomes is higher when vans are identified in SV crashes. Drivers' overtaking actions will significantly increase SV crash injury severities. Although some common attributes, such as alcohol impaired driving, are significant in both SV and MV crash severity models, their effects on different injury outcomes vary substantially. This study provides a better understanding of similarities and differences in significant contributing factors and their impacts on driver injury severities between SV and MV crashes on rural two-lane highways. It is also helpful to develop cost-effective solutions or appropriate injury prevention strategies for rural SV and MV crashes.

Analysis of driver speeds under night driving conditions using a driving simulator

PROBLEM

Accident statistics demonstrate that there should be a greater focus on nighttime driving to improve our knowledge of driver behavior under poor lighting conditions. However, the current geometric design criteria do not take into account driving at night. Moreover, studies that propose predictive models of operating speed only consider daytime driving conditions.

METHOD

This study compares driver speed behavior during daytime and nighttime driving and models operating speeds and speed differentials, identifying significant factors that influence speed behavior under different lighting conditions. The research was carried out using a driving simulator for a section of an existing two-lane rural road composed of 39 tangent-curve configurations. Speed profiles were recorded for 40 drivers under simulated daytime and nighttime driving conditions.

RESULTS

New predictive speed models, differentiated for daytime and nighttime driving, are proposed that highlight the effects of different geometric predictors under different visibility conditions. Specifically, predictive models for operating speed on curves identified the inverse of the radius and the deflection angle of the curve as predictors under both driving conditions. For speed differentials based on the 85th percentile for maximum speed reduction (85 MSR), we found that the inverse of the approaching tangent length and of the curve radius significantly explained the dependent variable in both cases, with a higher dependence of nighttime 85 MSR on the curve geometry than on the tangent length. Tangent length had a significant effect on operating speed for independent tangents only for the daytime model, whereas the inverse of the previous radius was confirmed as a predictor for both visibility conditions.

PRACTICAL APPLICATIONS

This research may influence design considerations for nighttime driving by providing evidence of the effects of nighttime conditions on driver speed choices and road safety.

Driver performance approaching and departing curves: driving simulator study

OBJECTIVE

This article reports the outcomes of a driving simulator study on the driver performance approaching and departing curves. The study aimed to analyze driver performance in the tangent-curve-tangent transition and verify the assumption of constant speed in a curve that is commonly used in the operating speed profiles; test whether the 85th percentile of acceleration and deceleration rates experienced by drivers and the acceleration and acceleration rates obtained from the operating speeds are equivalent; find the explanatory variables associated with the 85th percentile of deceleration and acceleration rates experienced by drivers when approaching and departing horizontal curves and provide predicting models of these rates.

METHODS

A driving simulator study was carried out. Drivers' speeds were recorded on 26 configurations of the tangent-curve-tangent transition of 3 2-lane rural roads implemented in the CRISS (Inter-University Research Center for Road Safety) driving simulator; 856 speed profiles were analyzed.

RESULTS

The main results were the following: The simplified assumption of the current operating speed profiles that the speed on the circular curve is constant and equal to that at midpoint can be considered admissible; The 85th percentile of deceleration and acceleration rates exhibited by each driver best reflect the actual driving performance in the tangent-curve-tangent transition; Two models that predict the expected 85th percentile of the deceleration and acceleration rates experienced by drivers were developed.

CONCLUSIONS

The findings of the study can be used in drawing operating speed profiles that best reflect the actual driving performance and allow a more effective safety evaluation of 2-lane rural roads.

Effects of simulated day and night driving on the speed differential in tangent-curve transition: a pilot study using driving simulator

OBJECTIVE

The pilot study described in this article aimed to analyze the driver speed profile for evaluation of road design consistency during simulated day and nighttime driving. The research, carried out using a driving simulator, was developed with the overall objectives of evaluating the speed differential during simulated nighttime driving for the identification of critical road situations not detected by design consistency evaluation during simulated daytime driving.

METHODS

An existing 2-lane rural road, where high accident rates were recorded during nighttime, was implemented in the driving simulator of the Inter-University Research Centre of Road Safety (CRISS) and the drivers' speed profiles were recorded in both simulated day and nighttime driving conditions over the 39 tangent-curve configurations that composed the road alignment.

RESULTS

The analysis of the speed differential based on the 85MSR (Maximum Speed Reduction) indicator during simulated daytime driving was not able to identify critical road situations that the same analysis revealed during the simulated nighttime driving. Such results occurred for most of the tangent-curve configurations.

CONCLUSIONS

The study demonstrated that limiting the speed analysis only to daytime driving conditions cannot exclude the possibility that during nighttime driving some road configurations could become unsafe. The findings of the study highlight the need to carry out design consistency evaluations for nighttime driving conditions.

Detecting driver drowsiness based on sensors: a review

In recent years, driver drowsiness has been one of the major causes of road accidents and can lead to severe physical injuries, deaths and significant economic losses. Statistics indicate the need of a reliable driver drowsiness detection system which could alert the driver before a mishap happens. Researchers have attempted to determine driver drowsiness using the following measures: (1) vehicle-based measures; (2) behavioral measures and (3) physiological measures. A detailed review on these measures will provide insight on the present systems, issues associated with them and the enhancements that need to be done to make a robust system. In this paper, we review these three measures as to the sensors used and discuss the advantages and limitations of each. The various ways through which drowsiness has been experimentally manipulated is also discussed. We conclude that by designing a hybrid drowsiness detection system that combines non-intusive physiological measures with other measures one would accurately determine the drowsiness level of a driver. A number of road accidents might then be avoided if an alert is sent to a driver that is deemed drowsy.