Analytical Model for Sight Distance Analysis on Three-Dimensional Highway Alignments

Hassan, Yasser; Easa, Said M.; Halim, A O Abd El

doi:10.3141/1523-01

Cited by 53 publications

(21 citation statements)

References 4 publications

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“…Hassan et al [9] developed models that determined S av given offsets to continuous obstacles. Further studies were conducted to determine S av , mostly using methods that subdivided a highway and its surroundings into small geometric elements [10]- [17]. All these models are for evaluating whether or not the determined S av is greater than design sight distance given offsets to obstructions.…”

Section: Cosmentioning

confidence: 99%

New Spiral Curves for Appropriate Transition of Minimum Roadside Clearance on Simple Curves

Mauga¹

2015

JTTs

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Guidelines for geometric design of highways require that the inside of horizontal curves be cleared of obstructions to sight in order to provide necessary sight distance. Many of these guidelines use one analytical model for determining minimum clearance offsets. These offsets are suitable for middle sections of long curves because the analytical model was derived with consideration that drivers on the curves are able to see downstream curved sections whose lengths are equal to stopping sight distance. Applying these offsets to straight sections near beginnings and ends of the curves results in unnecessary clearance costs since sightlines are accommodated within lanes and wide shoulders. This paper presents a new analytical model for gradual transition of clearance from zero on straight sections to the minimum value required at the middle of horizontal curves. The model is based on new spiral curves whose mathematical equations incorporate driver location, object location, radius of horizontal curve, length of horizontal curve, and design sight distance. Moreover, the already known Euler's spiral curve is examined whether or not it is also suitable for transitioning clearance. It is found that the Euler's spiral consistently underestimates clearance offsets. Underestimation of the offsets is due to high degree of sharpness of the Euler's spiral which renders the spiral unsuitable for transitioning clearance. Finally, the analytical model is presented in the form of a design chart. Without compromising safety and mobility of highways, use of either the design chart or the analytical equations will help agencies save money that would otherwise be spent for unnecessary extra clearance of roadside areas near beginnings and ends of horizontal curves.

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Section: Cosmentioning

confidence: 99%

New Spiral Curves for Appropriate Transition of Minimum Roadside Clearance on Simple Curves

Mauga¹

2015

JTTs

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“…Several years later, Hassan et al [8] presented an analytical model for computing available sight distance on combined horizontal and vertical highway alignments, using parametric finite elements (four, six and eight-node rectangular elements as well as three-node triangular elements) to represent the highway and sight obstructions. The idea behind the proposed model is summarized in checking the driver's sight line, which is represented by a straight line between the driver's eye and an object, against all the possible sight obstructions, by using an iterative procedure.…”

Section: Ssd Modelingmentioning

confidence: 99%

Analytical Method for 3-D Stopping Sight Distance Adequacy Investigation

Mertzanis¹,

Boutsakis²,

Kaparakis³

et al. 2015

JCEA

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Abstract:The adopted 2-D SSD (stopping sight distance) adequacy investigation in current design practice may lead to design deficiencies due to inaccurate calculation of the available sight distance. Although this concern has been identified by many research studies in the past, none of them suggested a comprehensive methodology to simulate from a 3-D perspective concurrently both the cross-section design and the vehicle dynamics in space during emergency braking conditions. The proposed methodology can accurately perform SSD adequacy investigation in any 3-D road environment where the ground, road and roadside elements are inserted by identifying areas of interrupted vision lines between driver and obstacle being less than the required distance necessary to bring the vehicle to a stop condition. The present approach provides flexibility among every road design and/or vehicle dynamic parameter inserted, as well as direct overview regarding design elements that restrict the driver's vision and create SSD inadequacies. As a result, precious guidance is provided to the designer for further alignment improvement but mostly an accurate aid to implement geometric design control criteria with respect to both existing as well as new road sections is delivered. The efficiency of the suggested methodology is demonstrated through a case study.

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“…They implement a ray-tracing algorithm, but they run it in a triangulation instead directly in the point cloud as this work approaches. Another example using the ASD technique for visibility analysis in roads is the one proposed by Hassan, Easa, and El Halim [1996]. They use parametric finite elements, resulting in a quite expensive computational technique.…”

Section: Related Workmentioning

confidence: 99%

Interurban visibility diagnosis from point clouds

Iglesias

Díaz-Vilariño²,

González-Jorge

et al. 2016

European Journal of Remote Sensing

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We present an approach for automatic visibility analysis in interurban roads from point clouds. The methodology is based on a ray-tracing algorithm followed by an occlusion detection to identify potential obstacles between the driver and the theoretical position of pedestrians and cyclists. As a result, the area of visibility from each driver position is obtained. The method compares the performance and suitability of point clouds acquired from both Airborne and Mobile Laser Scanning. The methodology is tested in six real case studies. In most cases, results obtained from MLS are more accurate since the point clouds are acquired from a perspective similar to driver and they have higher resolution.

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Analytical Model for Sight Distance Analysis on Three-Dimensional Highway Alignments

Cited by 53 publications

References 4 publications

New Spiral Curves for Appropriate Transition of Minimum Roadside Clearance on Simple Curves

New Spiral Curves for Appropriate Transition of Minimum Roadside Clearance on Simple Curves

Analytical Method for 3-D Stopping Sight Distance Adequacy Investigation

Interurban visibility diagnosis from point clouds

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