01518717

Component

Since many differences exist in terms of the design of expressway mainline and ramps between Shanghai and foreign countries, it is necessary to evaluate the safety influencing factors on Shanghai Expressway exit ramps. 71 exit ramps were selected for statistical analysis and regression analysis with 4 models including Poisson (PO), Zero-inflated Poisson (ZIP), Negative binomial (NB), and negative binomial (ZINB). The results of ZINB model showed that ramp AADT, number of exit ramp lanes, the ramp slope, and the deceleration length significantly affect the safety of expressway exit ramps. Meanwhile, ramp type, the length from ramp terminal to the stop line of downstream intersection and the lane arrangement at downstream intersection are also significant factors in the PO, NB, ZIP models. The study demonstrated that: 1) The crash frequency of Type 4 (not lane-balanced) exit ramp is 46% more than that of Type 2 (lane-balanced) exit ramp; 2) within the 3 exit ramp slope types, uphill-to-ground shows the worst safety, while the best one is downhill-to-ground exit ramp; 3) compared with the conventional lane arrangement, crash frequency increases by 38% with the downstream left-turn lane placed on the right side. Finally, comparing the results of 4 models, it was founded that ZINB model can fit the crash data on exit ramps better. Furthermore, several suggestions about the design of exit ramp on expressways were put forward in the last.

This paper was sponsored by TRB committee ANB25 Highway Safety Performance. Alternate title: Safety Influencing Factor Assessment of Expressway Exit Ramps in Shanghai.

01503729

14-3640

English

17p

2014

Transportation Research Board 93rd Annual Meeting

Digital/other

Figures; Maps; References; Tables

Expressways; Geometric design; Highway factors in crashes; Off ramps; Regression analysis; Safety factors

Shanghai (China)

Design; Highways; Safety and Human Factors; I82: Accidents and Transport Infrastructure

Transportation Research Board Annual Meeting 2014 Paper #14-3640

TRIS, TRB, ATRI

Jan 27 2014 3:15PM