01628146

Component

https://doi.org/10.3141/2618-05

Despite the extensive implementations of unsignalized superstreets in practice, reliable methodologies for their geometric design remain unavailable. In recognition of the critical role of the U-turn offset length design, this study proposed an applicable tool to help traffic professionals determine the minimum required offset length for safety needs. The proposed model offers a convenient tool to evaluate a candidate design on the basis of traffic dynamics and driver gap acceptance behavior. In addition, this model can be used to assess whether installation of signals is needed to accommodate growing traffic. With the use of the surrogate safety assessment model as an unbiased tool, this study evaluated the safety performance of one superstreet with varied U-turn offset lengths (i.e., 700, 1,100, and 1,500 ft). Comparisons of the results of different designs indicated that the safety performance of the superstreet would not be compromised if the U-turn offset was reduced from 1,500 to 1,100 ft. However, more severe crashes were observed when the U-turn offset length was 700 ft. Further extensive analyses on different levels of demand also confirmed the need to properly design the offset length in an unsignalized superstreet.

01624541

17-02645

English

pp 48–57

2017

Transportation Research Record: Journal of the Transportation Research Board

9780309441919

Digital/other

Figures (5) ; References (27) ; Tables (6)

Evaluation and assessment; Gap acceptance; Geometric design; Offset intersections; Optimization; Traffic safety; U turns; Unsignalized intersections

Safety assessment; Superstreets

Design; Highways; Operations and Traffic Management; Safety and Human Factors

TRIS, TRB, ATRI

Dec 8 2016 11:00AM

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