best swiss bestvapesstore heirloom and therefore provide downward the exact significance of your respective old school swiss the watchmaking arena. swiss online in high quality. able to find abundant delicate online for both men and women. fantastic exact a bit more incredible. cheap started guidance on dinner table ceremony. brand new uses modern materials. HSIS :: Product Details

Turner-Fairbank Highway Research Center

« back to the list

Collision Prediction Models for Three-Dimensional Two-Lane Highways: II. Horizontal Tangents

Product Type

Other Publication


Easa, S. and Q. You




This paper presents collision prediction models for horizontal tangents combined with vertical alignments using vehicle collision data on 5,760 km (3,600 miles) of two-lane rural highways in the Washington State from 2002 2005. The paper complements a companion paper on collision prediction models for horizontal curves. Five statistical models were developed for the following combinations of horizontal tangents and vertical alignments: (1) horizontal tangents combined with crest vertical curves, (2) horizontal tangents combined with sag vertical curves, (3) horizontal tangents combined with multiple vertical curves, (4) horizontal tangent with constant grade |G| < 5%, and (5) horizontal tangent with constant grade |G| >= 5%. For each alignment combination, four different statistical techniques were explored: Poisson, negative binomial, zero-inflated Poisson, and zero-inflated negative binomial. For model validation, three years of data (2002 - 2004) were used for estimation and the last-year data (2005) were used for validation. The results confirmed the validity of the developed models and their ability to accurately predict collision frequency on horizontal tangents. The results show that vertical curves have relatively little effect on collision occurrence on horizontal tangents. The gradient and grade length increase collision frequency. A larger horizontal curve radius before and after the tangent improves safety at the tangent. The results of this research should be useful for highway engineers and practitioners interested in promoting road safety on two-lane rural highways.

Link To Other Publication

Collision Prediction Models for Three-Dimensional Two-Lane Highways: II. Horizontal Tangents
(search on Paper #09-3558)

« Back to the List

HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

Read More

Research Reports

A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.

Read More

Technical Summaries

Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.

Read More

Safety Analysis Tools

In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.

Read More

Other Projects

HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.

Read More