00741915

Component

https://doi.org/10.3141/1579-10

http://scholar.google.com...alim&publication_year=1997

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 this analytical model, computer software was developed and used in a preliminary application for 3-D headlight sight distances on a sag or crest vertical curve combined with a horizontal curve. The application showed that the 3-D sight distance on sag vertical curves was generally lower than the corresponding 2-D value when the sag curve was overlapping with a horizontal curve. On the other hand, the overlapping of horizontal curves with crest vertical curves enhanced the 3-D sight distance. The difference between 2-D and 3-D sight distance values in both cases increased with a decrease in the horizontal curve radius and an increase in the pavement cross slope. The model was proved to be extremely valuable in establishing 3-D highway geometric design standards.

This paper appears in Transportation Research Record No. 1579, Geometric Design and Its Effects on Operations.

English

p. 79-88

1997

Transportation Research Record

030906158X

Figures (9) ; References (12)

Alignment; Curves (Geometry); Finite element method; Geometric design; Highway curves; Highway design; Mathematical models; Night; Sight distance; Software

Analytical models; Horizontal curvature; Vertical curvature

Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Oct 6 1997 12:00AM

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• FIELD ANALYSIS OF OPERATION AND DESIGN OF SINGLE-POINT URBAN INTERCHANGES
• FORMULATION AND VALIDATION OF OPERATING SPEED-BASED DESIGN CONSISTENCY MODELS BY BOOTSTRAPPING
• GUIDELINES FOR OFFSETTING OPPOSING LEFT-TURN LANES ON DIVIDED ROADWAYS
• GUIDELINES FOR RIGHT-TURN TREATMENTS AT UNSIGNALIZED INTERSECTIONS AND DRIVEWAYS ON RURAL HIGHWAYS
• MODEL FOR MINIMUM DRIVEWAY CORNER CLEARANCES AT SIGNALIZED INTERSECTIONS
• OPERATING SPEED ON SUBURBAN ARTERIAL CURVES
• OPERATIONAL ASPECTS OF MICHIGAN DESIGN FOR DIVIDED HIGHWAYS
• OPERATIONAL IMPACT OF SPLIT INTERSECTIONS
• RURAL TWO-LANE PASSING HEADWAYS AND PLATOONING
• STATE-OF-THE-ART DESIGN OF ROUNDABOUTS