One of the important components of traffic simulation models is a car-following model that descri... more One of the important components of traffic simulation models is a car-following model that describes driver behaviour in a car-following situation. The existing car-following models have some limitations that may adversely affect the performance of in-vehicle rear-end collision warning systems. This paper presents a car-following model that addresses some limitations of the existing models. The proposed model considers the variations in the drivers' perceptionreaction time and the effect of the front and back vehicles in the car-following situation. The proposed model explicitly considers the driver's age and gender in car-following modeling. Actual vehicle tracking data obtained from the U.S. Federal Highway Administration were used to calibrate and validate the proposed model. The results of the proposed model closely match the actual speed and spacing profiles of the following vehicle.
Abstract: According to current highway design standards, horizontal and vertical alignments are t... more Abstract: According to current highway design standards, horizontal and vertical alignments are treated separately in two-dimensional (2D) projections. In this paper, a model developed by the writers is used to study the effects of considering three-dimensional (3D) alignment ...
Canadian Journal of Civil Engineering, Sep 1, 2007
Highway design consistency is one of the important criteria in selecting the geometric features o... more Highway design consistency is one of the important criteria in selecting the geometric features of proposed or existing alignments of two-lane rural highways. Operating-speed (OS) profile models have been used to evaluate design consistency by trial and error. For a proposed new highway, however, there may be geometric and physical constraints, and selection of these elements by trial and error to achieve optimal design consistency would be difficult, if not impossible. This paper presents an optimization model that establishes highway horizontal alignment to achieve maximum design consistency based on the OS profile. The decision variables of the model include radius of horizontal curves, spiral curve lengths, length of speed-change (SC) segments, and acceleration and deceleration rates. The objective function of the model minimizes the mean OS difference or the maximum OS difference for successive geometric features along the highway section. Application examples and sensitivity analysis are presented to illustrate the capabilities of the model in evaluating improvement strategies and to ensure that the model produces sound optimum alignments. The proposed model, which complements existing optimization models that mainly address highway construction cost, should be of interest to highway practitioners and engineers.
The main objectives of roundabout design are to maximize traffic safety and operational efficienc... more The main objectives of roundabout design are to maximize traffic safety and operational efficiency. Traditionally, because of the complexity of the system and the multiple objectives involved, the design process is iterative and time-consuming. A minor change in the geometry can result in significant changes in the system performance (operation and safety). This paper presents an optimization model that directly provides the roundabout geometry that optimizes two objectives: design consistency and operational efficiency. Design consistency is represented by the mean difference in operating speeds for various conflicting vehicle paths and operational efficiency is represented by the average roundabout delay. Vehicle paths (through, right, and left) and roundabout delay are modeled for all roundabout approaches. The input geometric data to the model can be easily obtained from an aerial photograph of the selected site using a geographic information systems (GIS) software. The system performance is optimized subject to geometric and traffic constraints. The proposed model is applicable to single-lane roundabouts (urban and rural) with four legs intersecting at right angles. Application of the model to an actual proposed roundabout site is presented. This proposed approach provides the optimum solution directly and is also more efficient than the traditional iterative approach. Key words: geometric design, roundabouts, horizontal curve, radius, optimization, consistency, capacity, traffic delay.
Canadian Journal of Civil Engineering, Dec 1, 2004
One of the main objectives to promote traffic safety at roundabouts is design consistency. Design... more One of the main objectives to promote traffic safety at roundabouts is design consistency. Design consistency ensures that the speed differences along a vehicle path or between conflicting paths are smaller than a specified criterion. Traditionally, roundabout design involves an iterative process. Initially, the vehicle path radii are determined from drawing each path by freehand on the proposed roundabout geometry, and then the speeds along path elements are calculated. The process is repeated until design consistency is satisfied. This paper presents an optimization model that directly provides the design parameters that maximize design consistency. The radii of different vehicle paths (through, right, and left) are mathematically modeled for given design parameters. The optimum design parameters include vehicle path radii, approach entry widths, inscribed circle diameter, circulating width, and central island diameter. The optimization model is applicable to single-lane roundabouts with four legs intersecting at right angles. The proposed model not only makes the design process more efficient, but also guarantees the optimum design consistency.Key words: geometric design, roundabouts, horizontal curve radius, consistency, safety, optimization.
Computer-aided Civil and Infrastructure Engineering, Oct 1, 2008
Highway agencies are continually facing safety problems on highways, especially on horizontal ali... more Highway agencies are continually facing safety problems on highways, especially on horizontal alignments. Traditionally, the geometric design implicitly considers safety through satisfying minimum design requirements for different geometric elements. This article presents a new substantive-safety approach for the design of horizontal alignments based not only on minimum design guidelines, but also on actual collision experience. The curve radii, spiral lengths, lane width, shoulder width, and tangent lengths are determined to optimize the mean collision frequency along the highway. The model allows the parameters of the horizontal alignment to vary within specified ranges. The model also considers any specified physical obstructions in selecting the optimal alignment. Collision experience is addressed using existing collision prediction models for horizontal alignments and cross sections. The model is applicable to two-lane rural highways for which collision prediction models exist. Application of the model is presented using numerical examples. The proposed substantive-safety approach takes horizontal alignment design one step further beyond the minimum-guideline concept, and therefore should be of interest to highway designers.
Ite Journal-institute of Transportation Engineers, Aug 1, 1998
This article presents an analytical method for establishing the vertical alignment of a highway s... more This article presents an analytical method for establishing the vertical alignment of a highway section using profile field data. This method eliminates the need to visually construct the highway vertical alignment when specific profile information is not available, therefore reducing the time and cost required for highway alignment preparation. Another advantage of the method is its usefulness in evaluating the adequacy of newly constructed highways in terms of adherence to the intended design standards. The method can also help the designer prepare alternative improvements to the alignment and evaluate them easily and efficiently. The method is coded into a computer program that determines the straight and curved segments of the highway and estimates the elevation, the instantaneous grade and the instantaneous rate of vertical curvature. A sample alignment and an actual alignment are presented.
Transportation Research Record: Journal of the Transportation Research Board, 1997
Sight distance is one of the major elements that must be considered in the geometric design to ac... more Sight distance is one of the major elements that must be considered in the geometric design to achieve safe and comfortable highways. Daytime sight distance has been extensively studied, and analytical models for two-dimensional (2-D) and three-dimensional (3-D) alignments have been developed. However, nighttime (headlight) sight distance has received less attention. Despite the higher accident rate during nighttime than during daytime, existing analytical models evaluating headlight sight distance are very primitive. Moreover, the interaction between the horizontal and vertical alignments has not been modeled. A four-phase analytical model for headlight sight distance on 3-D combined alignments is presented. The model is an application of the finite-element technique in highway geometric design. The model can determine the maximum distance that can be covered by the vehicle’s headlights and that is not obstructed by any sight obstructions including the road surface. On the basis of...
... Files: HRIS. Report Numbers: E-C003. Pagination: p. 35:1-13. Authors: Hassan, Y. Abd El Halim... more ... Files: HRIS. Report Numbers: E-C003. Pagination: p. 35:1-13. Authors: Hassan, Y. Abd El Halim, AO. Easa, SM. Publication Date: 1998-1. Serial: Transportation Research Circular Issue Number: E-C003 Publisher: Transportation Research Board ISSN: 0097-8515. Conference: ...
... Europe. Previous research work on highway geometric design consistency is categorized into th... more ... Europe. Previous research work on highway geometric design consistency is categorized into three main areas: (1) Speed considerations; (2) safety considerations; and (3) performance considerations. Speed considerations ...
One of the important components of traffic simulation models is a car-following model that descri... more One of the important components of traffic simulation models is a car-following model that describes driver behaviour in a car-following situation. The existing car-following models have some limitations that may adversely affect the performance of in-vehicle rear-end collision warning systems. This paper presents a car-following model that addresses some limitations of the existing models. The proposed model considers the variations in the drivers' perceptionreaction time and the effect of the front and back vehicles in the car-following situation. The proposed model explicitly considers the driver's age and gender in car-following modeling. Actual vehicle tracking data obtained from the U.S. Federal Highway Administration were used to calibrate and validate the proposed model. The results of the proposed model closely match the actual speed and spacing profiles of the following vehicle.
Abstract: According to current highway design standards, horizontal and vertical alignments are t... more Abstract: According to current highway design standards, horizontal and vertical alignments are treated separately in two-dimensional (2D) projections. In this paper, a model developed by the writers is used to study the effects of considering three-dimensional (3D) alignment ...
Canadian Journal of Civil Engineering, Sep 1, 2007
Highway design consistency is one of the important criteria in selecting the geometric features o... more Highway design consistency is one of the important criteria in selecting the geometric features of proposed or existing alignments of two-lane rural highways. Operating-speed (OS) profile models have been used to evaluate design consistency by trial and error. For a proposed new highway, however, there may be geometric and physical constraints, and selection of these elements by trial and error to achieve optimal design consistency would be difficult, if not impossible. This paper presents an optimization model that establishes highway horizontal alignment to achieve maximum design consistency based on the OS profile. The decision variables of the model include radius of horizontal curves, spiral curve lengths, length of speed-change (SC) segments, and acceleration and deceleration rates. The objective function of the model minimizes the mean OS difference or the maximum OS difference for successive geometric features along the highway section. Application examples and sensitivity analysis are presented to illustrate the capabilities of the model in evaluating improvement strategies and to ensure that the model produces sound optimum alignments. The proposed model, which complements existing optimization models that mainly address highway construction cost, should be of interest to highway practitioners and engineers.
The main objectives of roundabout design are to maximize traffic safety and operational efficienc... more The main objectives of roundabout design are to maximize traffic safety and operational efficiency. Traditionally, because of the complexity of the system and the multiple objectives involved, the design process is iterative and time-consuming. A minor change in the geometry can result in significant changes in the system performance (operation and safety). This paper presents an optimization model that directly provides the roundabout geometry that optimizes two objectives: design consistency and operational efficiency. Design consistency is represented by the mean difference in operating speeds for various conflicting vehicle paths and operational efficiency is represented by the average roundabout delay. Vehicle paths (through, right, and left) and roundabout delay are modeled for all roundabout approaches. The input geometric data to the model can be easily obtained from an aerial photograph of the selected site using a geographic information systems (GIS) software. The system performance is optimized subject to geometric and traffic constraints. The proposed model is applicable to single-lane roundabouts (urban and rural) with four legs intersecting at right angles. Application of the model to an actual proposed roundabout site is presented. This proposed approach provides the optimum solution directly and is also more efficient than the traditional iterative approach. Key words: geometric design, roundabouts, horizontal curve, radius, optimization, consistency, capacity, traffic delay.
Canadian Journal of Civil Engineering, Dec 1, 2004
One of the main objectives to promote traffic safety at roundabouts is design consistency. Design... more One of the main objectives to promote traffic safety at roundabouts is design consistency. Design consistency ensures that the speed differences along a vehicle path or between conflicting paths are smaller than a specified criterion. Traditionally, roundabout design involves an iterative process. Initially, the vehicle path radii are determined from drawing each path by freehand on the proposed roundabout geometry, and then the speeds along path elements are calculated. The process is repeated until design consistency is satisfied. This paper presents an optimization model that directly provides the design parameters that maximize design consistency. The radii of different vehicle paths (through, right, and left) are mathematically modeled for given design parameters. The optimum design parameters include vehicle path radii, approach entry widths, inscribed circle diameter, circulating width, and central island diameter. The optimization model is applicable to single-lane roundabouts with four legs intersecting at right angles. The proposed model not only makes the design process more efficient, but also guarantees the optimum design consistency.Key words: geometric design, roundabouts, horizontal curve radius, consistency, safety, optimization.
Computer-aided Civil and Infrastructure Engineering, Oct 1, 2008
Highway agencies are continually facing safety problems on highways, especially on horizontal ali... more Highway agencies are continually facing safety problems on highways, especially on horizontal alignments. Traditionally, the geometric design implicitly considers safety through satisfying minimum design requirements for different geometric elements. This article presents a new substantive-safety approach for the design of horizontal alignments based not only on minimum design guidelines, but also on actual collision experience. The curve radii, spiral lengths, lane width, shoulder width, and tangent lengths are determined to optimize the mean collision frequency along the highway. The model allows the parameters of the horizontal alignment to vary within specified ranges. The model also considers any specified physical obstructions in selecting the optimal alignment. Collision experience is addressed using existing collision prediction models for horizontal alignments and cross sections. The model is applicable to two-lane rural highways for which collision prediction models exist. Application of the model is presented using numerical examples. The proposed substantive-safety approach takes horizontal alignment design one step further beyond the minimum-guideline concept, and therefore should be of interest to highway designers.
Ite Journal-institute of Transportation Engineers, Aug 1, 1998
This article presents an analytical method for establishing the vertical alignment of a highway s... more This article presents an analytical method for establishing the vertical alignment of a highway section using profile field data. This method eliminates the need to visually construct the highway vertical alignment when specific profile information is not available, therefore reducing the time and cost required for highway alignment preparation. Another advantage of the method is its usefulness in evaluating the adequacy of newly constructed highways in terms of adherence to the intended design standards. The method can also help the designer prepare alternative improvements to the alignment and evaluate them easily and efficiently. The method is coded into a computer program that determines the straight and curved segments of the highway and estimates the elevation, the instantaneous grade and the instantaneous rate of vertical curvature. A sample alignment and an actual alignment are presented.
Transportation Research Record: Journal of the Transportation Research Board, 1997
Sight distance is one of the major elements that must be considered in the geometric design to ac... more Sight distance is one of the major elements that must be considered in the geometric design to achieve safe and comfortable highways. Daytime sight distance has been extensively studied, and analytical models for two-dimensional (2-D) and three-dimensional (3-D) alignments have been developed. However, nighttime (headlight) sight distance has received less attention. Despite the higher accident rate during nighttime than during daytime, existing analytical models evaluating headlight sight distance are very primitive. Moreover, the interaction between the horizontal and vertical alignments has not been modeled. A four-phase analytical model for headlight sight distance on 3-D combined alignments is presented. The model is an application of the finite-element technique in highway geometric design. The model can determine the maximum distance that can be covered by the vehicle’s headlights and that is not obstructed by any sight obstructions including the road surface. On the basis of...
... Files: HRIS. Report Numbers: E-C003. Pagination: p. 35:1-13. Authors: Hassan, Y. Abd El Halim... more ... Files: HRIS. Report Numbers: E-C003. Pagination: p. 35:1-13. Authors: Hassan, Y. Abd El Halim, AO. Easa, SM. Publication Date: 1998-1. Serial: Transportation Research Circular Issue Number: E-C003 Publisher: Transportation Research Board ISSN: 0097-8515. Conference: ...
... Europe. Previous research work on highway geometric design consistency is categorized into th... more ... Europe. Previous research work on highway geometric design consistency is categorized into three main areas: (1) Speed considerations; (2) safety considerations; and (3) performance considerations. Speed considerations ...
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