01555088

Component

American Association of State Highway and Transportation Officials (AASHTO) guideline for geometric design requires that objects on the inside of horizontal curves be cleared so that sufficient sight distance is provided. Roadside barriers are also recommended to be installed on the inside of the curves so as to lessen severity of run-off road accidents. Effective heights of these barriers may cause the barriers to encroach sightline space which is the space that contains sightlines from drivers to downstream dangerous objects. This study has developed and validated a methodology that uses alignment data as input to detect locations where roadside objects encroach the sightline space and to propose clearance such that required sight distance is guaranteed. The methodology uses cross section views with which interaction between the sightline space and roadside environment is analyzed automatically or visually. The interaction of the two is maximum where horizontal and crest curves overlap. At those locations, the room between the sightline space and the roadside surface is diminished such that fitting in barriers without the cross section analysis may end up in deficient sight distance. The cross section displays are visual decision support for designers to inspect existing sites and to develop sight distance solutions ranging from choice of barriers, location of barriers, flattening of back- slopes, to choice of highway radii. The methodology is simple and incorporable in current design software since the software already generate cross section views for roadway and roadside. Implementation of the methodology will be beneficial to areas of roadside design and maintenance.

This paper was sponsored by TRB committee AFB10 Geometric Design.

01550057

15-0068

English

18p

2015

Transportation Research Board 94th Annual Meeting

Digital/other

Figures; References; Tables

Barriers (Roads); Clearances (Navigation); Geometric design; Height; Highway curves; Highway safety; Line of sight; Roadside hazards

Crest curves; Sightline offsets

Design; Highways; Safety and Human Factors; I22: Design of Pavements, Railways and Guideways; I83: Accidents and the Human Factor

Transportation Research Board Annual Meeting 2015 Paper #15-0068

TRIS, TRB, ATRI

Dec 30 2014 12:11PM