00799063

Component

https://doi.org/10.3141/1701-11

http://scholar.google.com...mmes&publication_year=2000

A proposed speed profile model was used to estimate the reduction in 85th percentile speeds from the approach tangent to the midpoint of 1,126 horizontal curve sites on rural two-lane highways in three states. The sites were divided into eight speed-reduction intervals, the mean accident rate and mean speed reduction were computed for each category, and linear regression was performed to analyze the statistical relationship between mean accident rate and mean speed reduction. Similar analyses were performed with degree-of-curvature intervals to compare mean degree of curvature and mean speed reduction as predictors of accident experience. The results suggest that estimated speed reduction is a useful measure that helps explain how accident experience at horizontal curves on rural two-lane highways varies with degree of curvature. Horizontal curves that require speed reductions [generally, curves sharper than about 4 deg, a condition that corresponds with design speeds less than 100 km/h (60 mph) and estimated 85th percentile speeds less than drivers' desired speeds on long tangents] have higher accident rates than curves that do not require speed reductions. When curve sites are grouped into speed-reduction intervals, there is a statistically significant relationship between the intervals' mean accident rate and mean speed reduction. The mean accident rate increases approximately linearly with the mean speed reduction.

This paper appears in Transportation Research Record No. 1701, Design Speed, Operating Speed, and Sight Distance Issues.

English

p. 86-94

2000

Transportation Research Record

0309066808

Figures (4) ; References (12) ; Tables (5)

85th percentile speed; Crash rates; Curvature; Estimating; Mean (Statistics); Regression analysis; Rural highways; Two lane highways

Approach tangents; Horizontal curvature; Speed reduction; Speed-profile models

Data and Information Technology; Design; Highways; Planning and Forecasting; Safety and Human Factors; I21: Planning of Transport Infrastructure; I82: Accidents and Transport Infrastructure

TRIS, TRB, ATRI

Sep 29 2000 12:00AM

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