Roadside Configurations Research Articles

A Rural Road Accident Probability Model Based on Single-Vehicle Hazard Properties including Hazard Color and Mobility: A Driving Simulator Study

Road safety has recently been considered an important issue in the country. Single-vehicle accident statistics show the importance of this issue. From a safety viewpoint, drivers need to have a reasonable time window for hazard recognition and reaction; therefore, the hazard has to be in sight from a distance preferably longer than the standard minimum stopping sight distance. Nevertheless, if the roadside configuration makes the sight available for a very long distance, the hazard properties are the ones defining the visibility. The hazard size, color, and mobility are some of the most important hazard properties, which may mainly interact with ambient light (like being day or night) and driving speed. In this research, effect of hazard properties on driving accident likelihood was investigated in a condition that enough recognition and reaction time window was available for the driver to provide a ceteris paribus experiment. To fulfil that in a safe experiment condition, a driving simulator was used to test the behavior of 90 licensed drivers encountering an average of 14 hazards with various sets of properties. Based on the findings of this research, there are some interactions between influential hazard properties. The results imply that it is approximately 23% more likely to observe an accident when encountering a dark small stationary hazard at nighttime like a dark-colored with an observed size of 0.5 m × 0.5 m (e.g., a stone) than a major moving light-colored hazard in the daytime like a camel of 1.5 m ∗ 2 m in size. A green-colored hazard is 27% less likely to involve in an accident at nighttime than hazards with other colors. Each 10 km/h speed increment leads to 1.9% more accident likelihood, and every time the driver encounters a hazard, they will be 0.84% less likely to crash next time.

Vehicle’s lateral placement on horizontal curves: A literature review

The placement of vehicle within a curve is a crucial factor with regards to safety as it influences its frictional requirement. The lateral placement of vehicle can be defined as the lateral distance from the centreline or outer edge of the road to the front tire of the vehicle. Limited study has been documented in the literature regarding this crucial element that affects the friction demand. Studies have been conducted to measure the effectiveness of surface treatments that take vehicle placement as a factor for safety analysis, but a lesser number of studies have concentrated on developing lane placement as a statistical model and have relied on statistical tests for comparability. This paper begins with an overview of prior research on the lateral position in conjunction with speed, followed by the different data collecting methodologies and equipment. Later part of the paper discusses the impact of lateral placement and the different modelling approaches proposed in the past. The findings reveal that there is a need to study the lateral positioning of vehicles on curves in greater detail so that better prediction models can be developed. A wide range of considerations including continuous evaluation along different categories of curves with different vehicle types and roadside configurations are needed to enhanced the existing models.

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.

Evaluating the effect of vegetation and clear zone width on driver behavior using a driving simulator

Roadside vegetation provides a myriad of environmental and psychological benefits to drivers. While research has shown that natural landscapes cause less stress and frustration to the driver among other benefits, the same vegetation may potentially increase the severity of run-off-the-road crashes. The aim of this study was to evaluate the extent to which clear zone width and roadside vegetation density influence operating speeds and lateral positioning to determine whether the roadside environment has any effect on drivers’ attention to their speed. A within subject driving simulator experiment tested six combinations of clear zone widths and roadside vegetation densities. Participants’ driving performance was measured throughout the virtual drive. Along tangents and curves to the left, participants slowed down and drove closer to the centerline when trees were near the edge of the road. Similar to the results reported in Calvi (2015), no statistically significant differences in operating speeds were observed with change in vegetation density. The analysis of drivers’ eye movements indicated that the roadside configuration did not affect participants’ attention to their operating speed, however, the number of glances was highly correlated to the time spent in the virtual drive. The results provide evidence to suggest that, while the increased roadside vegetation density does not necessarily result in reduced driver speeds or deviated lateral positioning, the manipulation of the roadside clear zone width does provide tangible benefits to safe driver behavior. These research findings should be considered in the design of roadside elements, accounting for overstated benefits to roadside vegetation.

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

This paper reports the results of a driving simulator study which sought to analyze the effect that: (a) three roadside configurations on a two-lane rural road lined with trees have on speed and lateral position of the driver, depending on different cross-sections as well as geometric elements; (b) the beginning of the guardrail barrier has upon the driver's behavior whenever this occurs on the left curve, right curve or tangent.A two-lane rural road lined with trees was designed and implemented in an advanced-interactive driving simulator. Two different cross-sections (with and without a shoulder), which were combined with three roadside configurations (only trees, trees and barriers, trees and barriers having undergone a treatment), were tested. Six road scenarios were then analyzed. Thirty-six drivers (33 were deemed to be valid and used for the analysis) drove in the simulator using these scenarios and the speed and lateral placement values were collected.Statistical analysis showed that the driver behavior was only affected by the cross-sections and geometric elements but not by roadside configurations. Although the presence of trees along the road represents a factor that increases the severity of run-off-road accidents, drivers do not change their behavior when barriers are not present.Concerning the effects of the beginning of the barrier, MANOVA revealed a main effect for roadside configuration on lateral position but not on speed. There was also a clear tendency of drivers to “cut” both the right curves as well as the left curves in order to minimize the speed reduction in the tangent–curve–tangent transition. These main results allow useful suggestions to be made as regards safety measures for improving road safety on two-lane rural roads lined with trees.

Optimal configuration of roadside beacons in V2I communications

Dedicated Short Range Communication (DSRC) standards have been defined as the physical and MAC layers in the context of vehicular communications. In this work the performance of DSRC communications are analyzed in the context of roadside to vehicle environments for different traffic loads. Based on these results optimal configurations are proposed for the physical parameters of the roadside beacon: output power transmission, and antenna height and tilt, as well as for the length of the packets and the access mechanism. An accurate physical model was used, with actual antenna patterns intended for the 5.9 GHz band, suitable propagation models, and assuming capture effect in the packet error computation. Results show notable divergences among roadside configurations for different traffic loads and optimization criteria. Indeed, simulations have shown that a vast majority of errors come from simultaneous transmissions, suggesting the use of suitable link layer protocols.

Empirical calibration of a roadside hazardousness index for Spanish two-lane rural roads

Crash records and roadside data from Spanish two-lane rural roads were analyzed to study the effect of roadside configuration on safety. Four indicators were used to characterize the main roadside features that have an influence on the consequences of roadway departures: roadside slope, non-traversable obstacles distance from the roadway edge, safety barrier installation, and alignment. Based on the analysis of the effect of roadside configuration on the frequency and severity of run-off-road injury crashes, a categorical roadside hazardousness scale was defined. Cluster analysis was applied to group the combinations of the four indicators into categories with homogeneous effects on run-off-road injury crashes frequency and severity. As a result a 5-level Roadside Hazardousness Index (RHI) was defined. RHI can be used as reference to normalize the collection of roadside safety related information. The index can also be used as variable for inclusion of roadside condition information in multivariate crash prediction models.

ROADSIDE HAZARD SIMULATION MODEL ITS DEVELOPMENT AND APPLICATION

The consequences of vehicle interactions, collisions, with objects and other roadside features depend on many factors such as vehicle speed, mass and rigidity; object dimensions, mass and strength; the number of vehicle occupants, their physical condition and age and whether or not occupant restraint systems are used. In order to estimate the relative safety of a variety of roadside configurations and hazard characteristics the Roadside Hazard Simulation Model (RHSM) was developed for Transport Canada in the late 1970's primarily as an efficient tool for comparing various roadside designs and obstacles over a wide range of encroachment conditions. Twenty simulation runs were made with RHSM Version 6 covering 10 terrain and roadside object conditions for two vehicle sizes. The simulation results show that the occupants of small vehicles suffer higher probability of injury/fatality than do occupants of large vehicles when they crash with roadside objects such as poles and barriers.