Consideration of Sight Distance in Placement of Concrete Barriers on Horizontal Curves of Roads

Sarhan, Mohamed; Hassan, Yasser

doi:10.3141/2301-02

Cited by 14 publications

(13 citation statements)

References 12 publications

(11 reference statements)

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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%

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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%

“…Equation (17) Equation (15). The coefficient C 5 is calculated by inserting the upper limit of the domain of Equation (17). When a driver is at PT, d S L = + and the object is at PT S + hence H T S = .…”

Section: Case 2(c): Driver On the Curve And Object On The Receding Tamentioning

confidence: 99%

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

Mauga¹

2015

JTTs

View full text Add to dashboard Cite

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“…Barriers may also be placed in the median area to prevent out-of-control vehicles in one direction from crossing to the other road direction, in which case they are called median barriers. The presence of median barriers on left-turn curved divided highways, although they increase the level of safety, under certain circumstances may affect the sight distance available to drivers [27].…”

Section: Median Barrier Design On Divided Highwaysmentioning

confidence: 99%

“…Sarhan et al [27] using previously developed software, examined the impact of roadside and median barriers on the available SSD on horizontal curves when overlapped with various vertical alignments. The results confirmed previous findings according to which the available sight distance depends on the type of the vertical alignment and the curvature of crest or sag vertical curves overlapping on the horizontal curve.…”

Section: Existing Sight Distance Approach On Left Curved Divided Highmentioning

confidence: 99%

Three-dimensional stopping sight distance control on passing lanes of divided highways

Mavromatis

Mertzanis

Kleioutis

et al. 2016

Eur. Transp. Res. Rev.

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Introduction Stopping Sight Distance control of passing lanes of divided highways represents currently a discussion point among researchers. A 3-D approach to address the issue is accepted as the overall solution to the problem by both researchers and contemporary design policies. This paper aims to contribute to the problem by presenting a sound and practical design solution to it with an analytic and a design values based format. Methods The solution approach consists of both a realistic description of the 3-D highway configuration and a 3-D vehicle kinematics calculation of the stopping maneuver along the vehicle's actual path. A SSD control method, previously developed by the authors', that relates concurrently the 3D configuration of a roadway to the kinematics of a vehicle moving along the actual roadway path, is applied, as a tool for the assessment of critical design parameters directly related to SSD adequacy. Results A rather comfortable alignment case consisting of a left curved divided highway overlapped with crest vertical curve parameters for numerous horizontal-vertical arrangements is examined, where an extensive area of SSD inadequacy during emergency braking procedure is reported. Conclusions The authors propose that the optimal solution to achieve SSD adequacy on left curved divided highways is to increase object height. This would preserve design consistency as well as driver expectations, by avoiding the need for lateral widening or site-specific speed limits. More specifically the object height is suggested to be equivalent to the driver's height of 1.08 m (AASHTO 2011). This would require additional stop lights on those vehicles whose stop lights are currently below this level. Although such a requirement regarding the current vehicle fleet is not feasible, vehicle industries as well as road design guidelines should address this issue in the near future.

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“…Sarhan and Hassan [4] analyzed available stopping sight distance (SSD) on horizontal curves with roadside or median barriers in 3 Dimension (3D) combined alignments by using finite element technique software. Their analysis confirmed the dependency between the available SSD on horizontal curves (due to road barriers) and overlapping vertical alignment.…”

Section: D Models Combining Horizontal and Vertical Alignmentsmentioning

confidence: 99%

Sight distance restriction on highways’ horizontal curves: insights and sensitivity analysis

Bassan¹

2016

Eur. Transp. Res. Rev.

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Consideration of Sight Distance in Placement of Concrete Barriers on Horizontal Curves of Roads

Cited by 14 publications

References 12 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

Three-dimensional stopping sight distance control on passing lanes of divided highways

Sight distance restriction on highways’ horizontal curves: insights and sensitivity analysis

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