Sight Distance for Stop-Controlled Intersections Based on Gap Acceptance

2000 ◽  
Vol 1701 (1) ◽  
pp. 32-41 ◽  
Author(s):  
Douglas W. Harwood ◽  
John M. Mason ◽  
Robert E. Brydia
Keyword(s):  
Travel Time ◽  
Field Studies ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicle ◽  
Sight Distance ◽  
Minor Road ◽  
Distance Model ◽  
Design Speed ◽  
A Minor

The current AASHTO policy for sight distance at Stop-controlled intersections is based on a model of the acceleration performance of a minor-road vehicle turning left or right onto a major road and the deceleration performance of the following major road vehicle. An alternative intersection sight distance model based on gap acceptance is developed and quantified. Field studies that were performed to determine the critical gaps appropriate for use in sight distance design are described. It is recommended that the sight distance along the major road for a passenger car at a Stop-controlled intersection should be based on a distance equal to 7.5 s of travel time at the design speed of the major road. Longer sight distances are recommended for minor-road approaches that have sufficient truck volumes to warrant consideration of a truck as the design vehicle.

Delays to road traffic at an intersection

1964 ◽  
Vol 1 (2) ◽  
pp. 297-310 ◽  
Author(s):  
G. F. Yeo ◽  
B. Weesakul
Keyword(s):  
Road Traffic ◽  
Partial Solution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicle ◽  
Mean Delay ◽  
Minor Road ◽  
The Mean ◽  
Stationary Waiting Time ◽  
A Minor

A model for road traffic delays at intersections is considered where vehicles arriving, possibly in bunches, in a Poisson process in a one way minor road yield right of way to traffic, which forms alternate bunches and gaps, in a major road. The gap acceptance times are random variables, and depend on whether or not a minor road vehicle is immediately following another minor road vehicle into the intersection or not.The transforms of the stationary waiting time and queue size distributions, and the mean stationary delay, for minor road vehicles are obtained by substitution of determined service time distributions into results for a generalisation of the M/G/1 queueing system. Some numerical results are given to illustrate the increase in the mean delay for variable gap acceptance times for a Borel-Tanner distribution of major road traffic, and a partial solution is given for a two way major road.

Delays to road traffic at an intersection

1964 ◽  
Vol 1 (02) ◽  
pp. 297-310 ◽  
Author(s):  
G. F. Yeo ◽  
B. Weesakul
Keyword(s):  
Road Traffic ◽  
Partial Solution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicle ◽  
Mean Delay ◽  
Minor Road ◽  
The Mean ◽  
Stationary Waiting Time ◽  
A Minor

A model for road traffic delays at intersections is considered where vehicles arriving, possibly in bunches, in a Poisson process in a one way minor road yield right of way to traffic, which forms alternate bunches and gaps, in a major road. The gap acceptance times are random variables, and depend on whether or not a minor road vehicle is immediately following another minor road vehicle into the intersection or not. The transforms of the stationary waiting time and queue size distributions, and the mean stationary delay, for minor road vehicles are obtained by substitution of determined service time distributions into results for a generalisation of the M/G/1 queueing system. Some numerical results are given to illustrate the increase in the mean delay for variable gap acceptance times for a Borel-Tanner distribution of major road traffic, and a partial solution is given for a two way major road.

scholarly journals Reliability Analysis of Sight Distance for Stopcontrol Intersections on Horizontal Alignments

2021 ◽  
Author(s):  
Altaf Hussain
Keyword(s):  
Extreme Values ◽  
Safety Margin ◽  
Random Variable ◽  
Probability Of Failure ◽  
Major Road ◽  
Road Design ◽  
Sight Distance ◽  
Minor Road ◽  
Reliability Method ◽  
Design Speed

Intersection sight distance (ISO) for stop-control intersections refers to the provision of adequate sight distance between a minor-road stopped vehicle and a major-road vehicle. The AASHTO policy for ISO for intersections on straight roadways Is based on the extreme values of the component design variables, such as major-road design speed and time gap, and assumes that these variables are deterministic. This research presents a reliability method that considers the moments (mean and variance) of the probability distribution of each random variable instead of the extreme values. This reliability method also accounts for the correlations among the component random variables. A performance function in terms of a safety margin is defined as the difference between the expected available and expected required ISO. Relationships for the mean and standard deviation of the safety margin are developed using First- Order Second-Moment analysis. Design graphs for the obstruction location are established for different radii of horizontal curves, design speed, and probability of failure. The reliability method is very useful as it provides the reliability associated with I8D design values. For evaluation purposes, the method can be used to determine the probability of failure of a particular intersection for an existing obstruction and current traffic conditions. The method can also be used to design the obstruction location for a given probability of failure. It was found that the deterministic method generally provides a higher probability of failure when the obstruction is closer to the minor road.

scholarly journals Reliability Analysis of Sight Distance for Stopcontrol Intersections on Horizontal Alignments

2021 ◽  
Author(s):  
Altaf Hussain
Keyword(s):  
Extreme Values ◽  
Safety Margin ◽  
Random Variable ◽  
Probability Of Failure ◽  
Major Road ◽  
Road Design ◽  
Sight Distance ◽  
Minor Road ◽  
Reliability Method ◽  
Design Speed

Intersection sight distance (ISO) for stop-control intersections refers to the provision of adequate sight distance between a minor-road stopped vehicle and a major-road vehicle. The AASHTO policy for ISO for intersections on straight roadways Is based on the extreme values of the component design variables, such as major-road design speed and time gap, and assumes that these variables are deterministic. This research presents a reliability method that considers the moments (mean and variance) of the probability distribution of each random variable instead of the extreme values. This reliability method also accounts for the correlations among the component random variables. A performance function in terms of a safety margin is defined as the difference between the expected available and expected required ISO. Relationships for the mean and standard deviation of the safety margin are developed using First- Order Second-Moment analysis. Design graphs for the obstruction location are established for different radii of horizontal curves, design speed, and probability of failure. The reliability method is very useful as it provides the reliability associated with I8D design values. For evaluation purposes, the method can be used to determine the probability of failure of a particular intersection for an existing obstruction and current traffic conditions. The method can also be used to design the obstruction location for a given probability of failure. It was found that the deterministic method generally provides a higher probability of failure when the obstruction is closer to the minor road.

Gap-acceptance in road traffic

1968 ◽  
Vol 5 (1) ◽  
pp. 84-92 ◽  
Author(s):  
A. G. Hawkes
Keyword(s):  
Simple Model ◽  
Service Time ◽  
Time Distribution ◽  
Road Traffic ◽  
Service Time Distribution ◽  
Major Road ◽  
Gap Acceptance ◽  
Road Vehicles ◽  
Minor Road ◽  
Acceptance Function

We find the distribution of delay to minor road vehicles waiting to merge or cross a single stream of major road traffic. The decision to cross is taken on the basis of a gap-acceptance function. The model turns out to be a simple queueing problem in which a customer finding an empty queue has a different service time distribution from queueing customers. The key to this representation is given in Section 3. Some numerical results in Section 6 indicate that in most circumstances a simple model will give adequate results.

The capacity of an intersection with non-stationary traffic

1976 ◽  
Vol 13 (02) ◽  
pp. 418-422
Author(s):  
Helmut Wegmann
Keyword(s):  
Road Traffic ◽  
Intensity Function ◽  
Major Road ◽  
Homogeneous Case ◽  
Homogeneous Poisson Process ◽  
Periodic Intensity ◽  
Minor Road ◽  
Traffic Stream ◽  
A Minor ◽  
Non Homogeneous Poisson Process

The average number of vehicles being able to enter an intersection per time unit from a minor road with a stop or yield sign — the capacity of the intersection — depends on the density of the traffic stream on the major road. In case the time-process of the major road traffic at the intersection is a non-homogeneous Poisson process with a periodic intensity function the capacity is calculated and compared with the capacity in the homogeneous case.

scholarly journals Modelling of Three-Dimensional Intersection Sight Distance

2021 ◽  
Author(s):  
Muhammad Zain Abrahim Ali
Keyword(s):  
Three Dimensional ◽  
Design Element ◽  
Major Road ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Left Turn ◽  
Horizontal Curves ◽  
Sight Distance ◽  
Minor Road ◽  
Left Turns

Intersection sight distance(ISD) is an important design element. Each intersection has a potential for several different types of vehicular conflicts that can be greatly reduced through the provision of proper sight distance. Current guidelines do not adequately address sight distance requirements for intersections located on horizontal curves alone or horizontal curves combined with vertical alignments. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. In many practical situations, however, sight distance is required to be checked for an existing or proposed three-dimensional(3D) intersection alignments. In this thesis, models were developed to check sight (2001) were considered on 3D alignment: (1)Departure from stop-control minor-road and (2) Left-turns from major-road. For stop-control intersections, several cases were addressed. These include Case 1(a): Intersection and approaching vehicle (object) lie on the curve, Case 2: Intersection lies on the tangent and object lies on the curve. For both cases (1) and (2), obstruction may lie inside or outside the horizontal curve and the intersection and object can be anywhere with respect to the vertical alignment. Design aids for required minimum lateral clearance (from the minor and major roads) are presented for different radii of intersections located on horizontal curves, guidelines are presented for offsetting opposing left-turn lanes to provide unobstructed required sight distance. Applications of the methodologies are illustrated using numerical examples.

scholarly journals Sight distances at unsignalized intersections: a comparison of guidelines and requirements for human drivers and autonomous vehicles

2021 ◽  
Vol 59 (3) ◽  
pp. 7-19
Author(s):  
Zsófia Magyari ◽  
Csaba Koren ◽  
Mariusz Kieć ◽  
Attila Borsos
Keyword(s):  
Autonomous Vehicles ◽  
Traffic Accidents ◽  
Human Vision ◽  
Design Parameters ◽  
Major Road ◽  
Gap Acceptance ◽  
Human Capabilities ◽  
Road Design ◽  
Unsignalized Intersections ◽  
Minor Road

Many traffic accidents are caused by unforeseen and unexpected events in a site that was hidden from the driver's eyes. Road design parameters determining required visibility are based on relationships formulated decades ago. It is worth reviewing them from time to time in the light of technological developments. In this paper, sight distances for stopping and crossing situations are studied in relation to the assumed visual abilities of autonomous vehicles. Current sight distance requirements at unsignalized intersections are based among others on speeds on the major road and on ac-cepted gaps by human drivers entering or crossing from the minor road. Since these requirements vary from country to country, regulations and sight terms of a few selected countries are compared in this study. From the comparison it is remarkable that although the two concepts, i.e. gap acceptance on the minor road and stopping on the major road have different backgrounds, but their outcome in terms of required sight distances are similar. Both distances are depending on speed on the major road: gap sight distances show a linear, while stopping sight distances a parabolic function. In general, European SSD values are quite similar to each other. However, the US and Australian guidelines based on gap acceptance criteria recommend higher sight distances. Human capabilities and limitations are considered in sight field requirements. Autonomous vehicles survey their environment with sensors which are different from the human vision in terms of identifying objects, estimating distances or speeds of other vehicles. This paper compares current sight field requirements based on conventional vehicles and those required for autonomous vehicles. Visibility requirements were defined by three vision indicators: distance, angle of view and resolution abilities of autonomous cars and human drivers. These indicators were calculated separately for autonomous vehicles and human drivers for various speeds on the main road and for intersections with 90° and 60° angles. It was shown that the required sight distances are 10 to 40 meters shorter for autonomous vehicles than for conventional ones.

The capacity of an intersection with non-stationary traffic

1976 ◽  
Vol 13 (2) ◽  
pp. 418-422 ◽  
Author(s):  
Helmut Wegmann
Keyword(s):  
Road Traffic ◽  
Intensity Function ◽  
Major Road ◽  
Homogeneous Case ◽  
Homogeneous Poisson Process ◽  
Periodic Intensity ◽  
Minor Road ◽  
Traffic Stream ◽  
A Minor ◽  
Non Homogeneous Poisson Process

The average number of vehicles being able to enter an intersection per time unit from a minor road with a stop or yield sign — the capacity of the intersection — depends on the density of the traffic stream on the major road. In case the time-process of the major road traffic at the intersection is a non-homogeneous Poisson process with a periodic intensity function the capacity is calculated and compared with the capacity in the homogeneous case.

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