00769388

Component

https://doi.org/10.3141/1658-02

http://scholar.google.com...mbro&publication_year=1999

Although the design policies of many countries encourage the use of spiral transition curves, questions exist about whether they have any benefit in roadway design. In addition, United States speed prediction models do not account for the presence of spiral transitions. To determine if spiral transitions affect the speed at which vehicles traverse horizontal curves on rural two-lane roadways, speeds of free-flow passenger cars on spiral transition curves were compared with speeds of free-flow passenger cars on circular curves that had similar geometric characteristics. Operating speeds and geometric data were collected at 12 spiral transition curves and 39 circular curves in six states. Using regression techniques, it was concluded that spiral transitions did not significantly affect the 85th percentile speed of drivers on horizontal curves. Analysis of the cumulative speed distributions for different curve radii showed that speeds were higher for spiral transition curves than for circular curves for a 145-m radius (smallest radii studied); however, no data were available to test the hypothesis further. It is believed that spiral transition curves may affect vehicle speeds as the curve radius decreases. It was concluded that spiral transitions did not produce significant differences in passenger-car operating speeds.

This paper appears in Transportation Research Record No. 1658, Highway Geometric Design and Operational Effects Issues.

English

p. 9-16

1999

Transportation Research Record

0309070554

Figures (6) ; References (17) ; Tables (5)

85th percentile speed; Highway curves; Highway design; Operating speed; Radius; Regression analysis; Rural highways; Speed distribution; Spirals; Two lane highways

Circular curves; Horizontal curvature

Data and Information Technology; Design; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Sep 8 1999 12:00AM

• A KNOWLEDGE-BASED GIS APPROACH TO THE EVALUATION OF DESIGN CONSISTENCY OF HORIZONTAL ALIGNMENTS
• DISTRIBUTION OF ROADWAY GEOMETRIC DESIGN FEATURES CRITICAL TO ACCOMMODATION OF LARGE TRUCKS
• EVALUATION OF ZERO-LENGTH VERTICAL CURVES
• LITTLE FALLS, GORHAM: RECONSTRUCTION TO A MODERN ROUNDABOUT
• LOCATION AND CONFIGURATION OF PASSING LANES
• RELATIONSHIP TO SAFETY OF GEOMETRIC DESIGN CONSISTENCY MEASURES FOR RURAL TWO-LANE HIGHWAYS
• RELATIONSHIPS BETWEEN BALL BANK INDICATOR READINGS, LATERAL ACCELERATION RATES, AND VEHICULAR BODY-ROLL RATES
• ROADWAY WIDENING COSTS FOR GEOMETRIC DESIGN IMPROVEMENTS TO ACCOMMODATE POTENTIAL LARGER TRUCKS
• SCHOOL BUS DESIGN VEHICLE DIMENSIONS
• SPEED VARIABILITY ON RURAL TWO-LANE HIGHWAYS