Automated Calculation of Sight Distance from Horizontal Geometry

Lovell, David J.

doi:10.1061/(asce)0733-947x(1999)125:4(297)

Cited by 40 publications

(22 citation statements)

References 4 publications

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“…. The intercept of the equation is obtained from the maximum value of T H in Equation (13). The maximum value of T H in Equation (13) is obtained when a driver is at distance L downstream of PC-S. To obtain the value of the constant C 4 the location of driver corresponding to maximum offset is used.…”

Section: Case 2(a): Driver On the Approach Tangent And Object On The mentioning

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: Case 2(a): Driver On the Approach Tangent And Object On The mentioning

confidence: 99%

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

Mauga¹

2015

JTTs

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“…More tables are needed to cover a wide range of values of common tangents, which is possible for design guidelines. Other models on available sight distance were developed by Lovell and others [10]- [12]. Further work was done by Lovell and Iida [13] who developed an algorithm that used GPS data to determine the boundary of the roadside area to clear such that design sight distance was provided.…”

Section: Cosmentioning

confidence: 99%

Minimum Roadside Clearance Offsets on the Inside of Reverse Curves Based on Flat Spirals

Mauga¹

2015

JTTs

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Design guidelines require that high objects on the inside of horizontal curves be cleared so as to provide sufficient sight distance. An example of the guidelines that require such clearance is the AASHTO's Green Book. The Green Book has an analytical model for determining minimum clearance for a given design sight distance. The model is well suited for middle sections of long curves. Applying such clearance to sections near beginnings and ends of the curves and to sections where there is reverse of curvature will result in over-clearance. Over-clearance implies extra cost of earthwork where highways pass in cut zones. To avoid such extra costs the guideline suggests using the graphical method to determine exact clearance offsets. The graphical method is accurate but it is also tedious and time consuming. This study developed analytical models for efficiently determining clearance offsets that match the offsets determined with the graphical method. The offsets are ordinates from driver paths to flat roadside spirals that make the boundary of the roadside area to clear. Mathematical equations for the spirals comprise of terms related to highway speed (in the form of design sight distance), curve features, and driver locations. In turn, these terms define magnitudes of the offsets to the spirals. Combination of the terms results in many parameters to the extent of making difficult development of design charts for offsets. However, examining suitability of published offset charts for simple curves as estimates of offsets for sites with reverse curves leads to finding that the charts are suitable as long as the reverse curves have common tangents that are at least as long as 25% of design sight distance. For reverse curves with no common tangents, offset charts have been developed and presented in this paper. Practitioners can use these charts or the derived equations to determine clearance offsets for new sites as well as for existing sites that are deficient in design sight distance.

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“…While clothoid spirals are also used frequently for curve transitions, they do not lend themselves to closed-form geometric calculations [5]. Furthermore, their effect is to reduce the rate of change of curvature and spread it over a longer distance, giving a following vehicle more time to enter the curve and become aware of the new circumstances.…”

Section: Geometric Derivationmentioning

confidence: 99%

“…where R(δ) is the transformation matrix that effects a counter-clockwise rotation about the origin through an angle of δ radians (for examples of this form of vector algebra for highway design purposes, see [5,6]), and is given by…”

Section: Geometric Derivationmentioning

confidence: 99%

A Solution for the Dropout Problem in Adaptive Cruise Control Range Sensors

Son

Kim²,

Shin

2006

Lecture Notes in Computer Science

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Abstract. At the transition from a tangent section to a curved section, it is possible for a following vehicle with adaptive cruise control in car-following mode to lose track of the lead vehicle. This occurs because the lead vehicle enters the curve and its path diverges from the axis of the following vehicle, yet the following vehicle does not yet have lateral acceleration information that would induce its range sensor to bend according to the curvature of its own path. This is a temporary situation, but one that could have an impact on cruise control safety and appropriate algorithms. In this paper, the conditions of time and distance that produce this circumstance are derived. Examples are given using typical values of roadway and vehicle parameters. Finally, some conclusions regarding possible solutions are offered.

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Automated Calculation of Sight Distance from Horizontal Geometry

Cited by 40 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

Minimum Roadside Clearance Offsets on the Inside of Reverse Curves Based on Flat Spirals

A Solution for the Dropout Problem in Adaptive Cruise Control Range Sensors

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