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Title:

Random Parameter Framework for Two-Lane Rural Roadways: Findings from Washington State

Accession Number:

01592851

Record Type:

Component

Abstract:

This paper discusses a modeling framework for Safety Performance Function (SPF) estimation, based on explanatory variable type and modeling technique, for 31 crash classifications. The scope of this research was approximately 5,443 miles of two-lane rural highways in Washington State, with SPFs analyzed in terms of crash data, roadway geometry, and roadside features aggregated between 2002 and 2010. Model evolution involved traditional and advanced fixed parameter Negative Binomial (NB) SPF estimations, followed by segment specific estimations using Random Parameter Negative Binomial (RPNB) models, built on two homogeneous segment datasets, one with pure mid-block segments, and the other including intersection ranges. Model behavior was analyzed considering roadside information, existence of intersection segments, specific route effects, and parameter heterogeneity. It was found that roadside features could have a significant impact on route specific model performance, and that the magnitude for Incident Rate Ratio for Average Daily Traffic (ADT) was lesser in the total accident models on pure mid-block segments as compared to those including intersection ranges. Through the RPNB estimations, the logarithm of ADT, logarithm of segment length, and eight different roadway geometry characteristics were found to have segment specific varying effects on the predicted crash frequency across the 31 crash types. Over-dispersion values were significantly reduced when considering roadway geometry parameter heterogeneity across the crash types on two-lane rural highways, indicating the erroneous inflation of alpha due to the assumption of fixed parameters in NB models.

Supplemental Notes:

This paper was sponsored by TRB committee ANB20 Standing Committee on Safety Data, Analysis and Evaluation. Alternative Title: Heterogeneous Overdispersion Parameter and Random Parameter Negative Binomial Models for Two-Lane Rural Roadways: Findings from Washington State

Monograph Accession #:

01584066

Report/Paper Numbers:

16-5439

Language:

English

Corporate Authors:

Transportation Research Board

500 Fifth Street, NW
Washington, DC 20001 United States

Authors:

Hong, Jungyeol
Hariharan, Barad
Shankar, Venky
Venkataraman, Narayan
Huang, Shuaiqi
Kezhiyur, Alben Jose
Milton, John C
Van Schalkwyk, Ida

Pagination:

23p

Publication Date:

2016

Conference:

Transportation Research Board 95th Annual Meeting

Location: Washington DC, United States
Date: 2016-1-10 to 2016-1-14
Sponsors: Transportation Research Board

Media Type:

Web

Features:

Figures; References (22) ; Tables

Geographic Terms:

Washington (State)

Subject Areas:

Highways; Safety and Human Factors

Source Data:

Transportation Research Board Annual Meeting 2016 Paper #16-5439

Files:

TRIS, TRB, ATRI

Created Date:

Jan 12 2016 6:22PM