scholarly journals Practicing Engineers Conceptions of Sight Distance and Stopping Sight Distance within the Context of Highway Design

2020 ◽  
Author(s):  
Shane Brown ◽  
Shannon Davis ◽  
Chelsea Nicholas
Keyword(s):  
Highway Design ◽  
Sight Distance ◽  
Stopping Sight Distance

Driver Perception–Brake Response in Stopping Sight Distance Situations

1998 ◽  
Vol 1628 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Daniel B. Fambro ◽  
Rodger J. Koppa ◽  
Dale L. Picha ◽  
Kay Fitzpatrick
Keyword(s):  
Response Time ◽  
Performance Studies ◽  
Response Times ◽  
Highway Design ◽  
Braking Performance ◽  
Reaction Distance ◽  
State Highway ◽  
Sight Distance ◽  
Design Speed ◽  
Stopping Sight Distance

One of the most important requirements in highway design is the provision of adequate stopping sight distance at every point along the roadway. At a minimum, this sight distance should be long enough to enable a vehicle traveling at or near the design speed to stop before reaching a stationary object in its path. Stopping sight distance is the sum of two components–brake reaction distance and braking distance. Brake reaction distance is based on the vehicle’s speed and the driver’s perception–brake reaction time (PBRT). Four separate, but coordinated, driver braking performance studies measured driver perception–brake response to several different stopping sight distance situations. The results from the driver braking performance studies suggest that the mean perception–brake response time to an unexpected object scenario under controlled and open road conditions is about 1.1 s. The 95th percentile perception–brake response times for these same conditions was 2.0 s. The findings from these studies are consistent with those in the literature: that is, most drivers are capable of responding to an unexpected hazard in the roadway in 2.0 s or less. Thus, the American Association of State Highway and Transportation Officials’ perception–brake response time of 2.5 s encompasses most of the driving population and is an appropriate value for highway design.

Reliability indices for road geometric design

1992 ◽  
Vol 19 (5) ◽  
pp. 760-766 ◽  
Author(s):  
Francis P. D. Navin
Keyword(s):  
Reliability Index ◽  
Design Parameters ◽  
Limit States ◽  
Highway Design ◽  
Reliability Indices ◽  
The Road ◽  
Modifying Factors ◽  
Sight Distance ◽  
Margin Of Safety ◽  
Stopping Sight Distance

Highway engineers, when asked to state the safety of a particular design, are usually at a loss to give a single meaningful measure as is possible in structural or geotechnical engineering. This paper outlines a method to estimate the margin of safety and reliability index for isolated highway components. The stopping sight distance is used to demonstrate the method. The method uses the basic highway design equations. On the assumption that the variables are random, the expected value of the mean and the variance are estimated; and from these the margin of safety and the reliability index are calculated. The most likely combination of variables for the existing design condition may also be estimated. The variables included represent the characteristics of the driver, the vehicle, and the road surface.A method is proposed to specify the design parameter's value representing a road's strategic importance, the users, the vehicles, the drivers, the environment, the terrain, and the standard of design and construction. The apparent advantage of the proposed reliability-based method is that the designer must explicitly specify the importance of the modifying factors and may also more closely investigate the behaviour of the variables in the design parameters in the critical region near noncompliance. Key words: limit states design, stopping sight distance, safety, highway design, reliability.

Three-Dimensional, Probabilistic Highway Design

2008 ◽  
Vol 2060 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Mohamed Sarhan ◽  
Yasser Hassan
Keyword(s):  
Reliability Analysis ◽  
Probabilistic Approach ◽  
Three Dimensional ◽  
Design Parameters ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Highway Design ◽  
Side Slope ◽  
Sight Distance ◽  
Stopping Sight Distance

The potential usefulness of reliability analysis has recently been stressed in many engineering applications. Given the variability in the design parameters, a reliability-based probabilistic approach is well suited to replace the current deterministic highway design practice. However, progress in this regard is generally slow. In this study, the reliability analysis was used to estimate the probability of hazard (POH) that might result from insufficiency of sight distances. As an application, the available sight distance was checked against required stopping sight distance on an assumed road segment. Variation of the design parameters was addressed with Monte Carlo simulation using 100,000 sets of design parameters based on distributions available in the literature. A computer program was developed to use these sets of design parameters to calculate the profiles of available and required stopping sight distances in two- and three-dimensional projections as well as the profile of POH. The approach was applied to a horizontal curve overlapping with flat grade, crest curves, and sag curves in a cut section where the side slope would restrict the sightline. The analysis showed that the current deterministic approach yields very conservative estimates of available and required stopping sight distance, resulting in very low POH. The application example also showed the change of POH with the change of vertical alignment parameters.

scholarly journals Empirical modeling of the relationship between decision sight distance and stopping sight distance based on AASHTO

2018 ◽  
Vol 4 (48) ◽  
pp. 7-25
Author(s):  
Shy BASSAN
Keyword(s):  
Friction Coefficient ◽  
Empirical Relationship ◽  
Design Guidelines ◽  
Empirical Modeling ◽  
Highway Design ◽  
Deceleration Rate ◽  
Sight Distance ◽  
Rough Approximation ◽  
Stopping Sight Distance ◽  
The Relationship

The paper introduces implementation of highways' stopping sight distance (SSD) and decision sight distance (DSD) based on AASHTO modeling assumptions. SSD characterizes the necessary distance for highway vehicles to stop safely in front from an obstacle. SSD is a function of vehicle speed, perception reaction time, deceleration rate, and grade based on AASHTO and most highway design international guidelines. The deceleration rate which is assumed constant (3.4 m/sec2) based on AASHTO 2011 is generally controlled by the friction coefficient depending on the road surface conditions. A driver's demanded deceleration rate may not exceed the range of friction coefficient according to various pavement conditions. Although SSD is generally sufficient to allow skilled and alert drivers to the stop their vehicles under regular situations, this distance is insufficient when information is difficult to comprehend. A DSD should be provided in highways geometric design when the driver is required to detect an unexpected or difficult to perceive information source. Interchanges (specifically exit ramps) and intersections, and required changing in driver direction of travel, changes in the basic cross section such as toll plaza, lane drop, are typical scenarios where driver needs DSD in the safety manner. The introduction of the two sight distance types (SSD and DSD) is a perquisite for empirical modeling of the relationship between DSD and SSD. The modeling refers to DSD for rural highways, suburban roads, and urban roads based on AASHTO models. Specifically the paper covers DSD three avoidance maneuver types of stopping (types A, A1, B) and three maneuver types of speed, path, and direction changing (types C,D, E) for the three roadway categories. The major parameters that control these avoidance types are pre-maneuver times, and pre-maneuver plus maneuver times. The empirical relationship proposed in this study simplifies the process of evaluating the decision sight distance based on stopping sight distance record, based on AASHTO models, without the need of strenuous estimation of the DSD model maneuver and deceleration parameters. Such a simplified correlation has not been found in the literature except a rough approximation documented in the British highway design guidelines.

Coupling Impacts of Spray and Rainfall on Road Visibility and Vehicle Speeds: A Simulation-based Analysis

2021 ◽  
Author(s):  
Shuyi Wang ◽  
Tianheng Chen ◽  
Bin Yu ◽  
Yue Sun ◽  
Xiaochun Qin
Keyword(s):  
High Speed ◽  
Traffic Accidents ◽  
Water Film ◽  
Design Parameters ◽  
Vehicle Speed ◽  
Highway Design ◽  
The Road ◽  
Sight Distance ◽  
Rain Medium ◽  
Stopping Sight Distance

Impaired visibility resulting from rainfall contributes greatly to the occurrence of traffic accidents. This study presents a numerical simulation approach to analyze the extent to which the coupling of spray and raindrops reduces visibility and thus proposes safe speeds against inadequate visibility. The spray-raindrop coupling particles were modeled by considering the real highway design parameters and rainfall conditions. The road visibility was estimated through simulating the multiple scattering process of taillights in the spray-rain medium, and the maximum safe speed against inadequate visibility was then derived by comparing the visibility with the required stopping sight distance. Results show that: 1) either a high speed of the front truck or a thick water-film results in a significant reduction in road visibility and the maximum safe speed of the ego vehicle, 2) front vehicle speed plays a more important role in visibility reduction than the water-film thickness does.

Sight distance red zones on combined horizontal and sag vertical curves

1998 ◽  
Vol 25 (4) ◽  
pp. 621-630 ◽  
Author(s):  
Yasser Hassan ◽  
Said M Easa
Keyword(s):  
Quantitative Analysis ◽  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Horizontal Curve ◽  
Sight Distance ◽  
Stopping Sight Distance ◽  
Three Dimensional Models ◽  
Highway Alignment ◽  
Current Standards

Coordination of highway horizontal and vertical alignments is based on subjective guidelines in current standards. This paper presents a quantitative analysis of coordinating horizontal and sag vertical curves that are designed using two-dimensional standards. The locations where a horizontal curve should not be positioned relative to a sag vertical curve (called red zones) are identified. In the red zone, the available sight distance (computed using three-dimensional models) is less than the required sight distance. Two types of red zones, based on stopping sight distance (SSD) and preview sight distance (PVSD), are examined. The SSD red zone corresponds to the locations where an overlap between a horizontal curve and a sag vertical curve should be avoided because the three-dimensional sight distance will be less than the required SSD. The PVSD red zone corresponds to the locations where a horizontal curve should not start because drivers will not be able to perceive it and safely react to it. The SSD red zones exist for practical highway alignment parameters, and therefore designers should check the alignments for potential SSD red zones. The range of SSD red zones was found to depend on the different alignment parameters, especially the superelevation rate. On the other hand, the results showed that the PVSD red zones exist only for large values of the required PVSD, and therefore this type of red zones is not critical. This paper should be of particular interest to the highway designers and professionals concerned with highway safety.Key words: sight distance, red zone, combined alignment.

scholarly journals An Initial Investigation of the Effects of a Fully Automated Vehicle Fleet on Geometric Design

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
John Khoury ◽  
Kamar Amine ◽  
Rima Abi Saad
Keyword(s):  
Autonomous Vehicles ◽  
Autonomous Vehicle ◽  
Real Life ◽  
Geometric Design ◽  
Design Elements ◽  
Sight Distance ◽  
Human Driver ◽  
Projected Change ◽  
Vehicle Fleet ◽  
Stopping Sight Distance

This paper investigates the potential changes in the geometric design elements in response to a fully autonomous vehicle fleet. When autonomous vehicles completely replace conventional vehicles, the human driver will no longer be a concern. Currently, and for safety reasons, the human driver plays an inherent role in designing highway elements, which depend on the driver’s perception-reaction time, driver’s eye height, and other driver related parameters. This study focuses on the geometric design elements that will directly be affected by the replacement of the human driver with fully autonomous vehicles. Stopping sight distance, decision sight distance, and length of sag and crest vertical curves are geometric design elements directly affected by the projected change. Revised values for these design elements are presented and their effects are quantified using a real-life scenario. An existing roadway designed using current AASHTO standards has been redesigned with the revised values. Compared with the existing design, the proposed design shows significant economic and environmental improvements, given the elimination of the human driver.

scholarly journals Three-Dimensional Stopping Sight Distance Calculation Method under High Slope Restraint

2020 ◽  
Vol 10 (20) ◽  
pp. 7118
Author(s):  
Yonghong Yang ◽  
Jiecong Wang ◽  
Yuanbo Xia ◽  
Lan Huang
Keyword(s):  
Calculation Method ◽  
Three Dimensional ◽  
Highway Safety ◽  
Small Radius ◽  
Safety Engineering ◽  
Design Data ◽  
Important Indicator ◽  
High Slope ◽  
Sight Distance ◽  
Stopping Sight Distance

Sight distance is an important indicator to ensure the safety of drivers, and is also an indispensable evaluation basis in highway safety engineering. In mountainous highways, high slopes and small radius often lead to poor visibility and traffic accidents. Through the combined calculation of horizontal and vertical sections, this paper comprehensively considers the specific sizes of roadside clearance, high slope, as well as the position and height of the driver’s view point and other factors, and it analyzes the limited visibility of the driver in the process of driving right turn. An effective and simplified calculation method based on design data for three dimensional (3D) stopping sight distance (S.S.D.) in high fill sections is proposed. Finally, the S.S.D. inspection of the actual highway, based on design speed and operating speed, is carried out, and the sight distance of the calculated point is judged by comparing the value with the normal value and the calculation result of the horizontal sightline offset. The results show that the method proposed in this paper is consistent with the sight distance results obtained by the horizontal sightline offset method, which indicates the calculation method is accurate and provides a technical reference for S.S.D. evaluation in highway safety engineering.

Location-based analysis of car-following behavior during braking using naturalistic driving data

2020 ◽  
Vol 47 (5) ◽  
pp. 498-505 ◽  
Author(s):  
Mostafa H. Tawfeek ◽  
Karim El-Basyouny
Keyword(s):  
Driver Assistance Systems ◽  
Behavioral Measures ◽  
Car Following ◽  
Sight Distance ◽  
Influence Area ◽  
Data Source ◽  
Naturalistic Driving ◽  
Stopping Sight Distance ◽  
Microscopic Modeling ◽  
Rich Data

This study investigates the car-following behavior during braking at intersections and segments. Car-following events were extracted from a naturalistic driving dataset, mapped using ArcGIS, and analyzed to differentiate between the intersection- and segment-related events. The intersection-related events were identified according to an intersection influence area, which was estimated based on the stopping sight distance and the speed limit. Five behavioral measures were quantified based on exploring the probability density functions (PDF) for intersection- and segment-related events. The results showed that there were significant differences between the PDFs of the measures for both cases. Moreover, it was indicated that drivers tend to be more aggressive at intersections compared with segments. Thus, it is crucial to consider the driver’s location when investigating driver behavior. The quantified behavioral measures are a rich data source that can be used for car-following microscopic modeling, surrogate safety analysis, and driver assistance systems development.

Sign in / Sign up

Export Citation Format

Share Document