01474111

Component

The Diverging Diamond Interchange (DDI) has quickly gained popularity across the United States due to its ability to improve traffic operations and safety with significant cost savings. As of August 2012, thirteen DDIs have been opened to traffic in the United States with the first one opening in July 2009 in Springfield, Missouri. Dozens more are either under construction or are in the final stages of design. The DDIs that have been constructed have many similar elements to the first Springfield DDI, but there are also many noticeable differences. This paper investigates a dozen different design elements of eight operational DDIs in the US and analyzes how those elements may affect the safety and/or operations of the interchange. The main goals of the research are to understand the operational effects of the different design elements within the DDI, separate theory and antidotal evidence from reality and science, and prioritize the important elements within the DDI. The biggest lesson learned from these operational DDIs is that there needs to be a greater emphasis on sight distance in the design. This relates to viewing signs and signal heads properly. It also relates to decision, stopping, and intersection sight distance issues. Other lessons learned include using signing and striping properly, giving drivers clear guidance, and that there are several acceptable ways to design elements within the DDI as long as there is an attention to detail.

This paper was sponsored by TRB committee AHB65 Operational Effects of Geometrics.

01470560

13-4023

English

10p

2013

Transportation Research Board 92nd Annual Meeting

Digital/other

References; Tables

Crossovers; Design; Diamond interchanges; Road markings; Sight distance; Traffic signals

Design; Highways; Operations and Traffic Management; I22: Design of Pavements, Railways and Guideways; I73: Traffic Control

Transportation Research Board Annual Meeting 2013 Paper #13-4023

TRIS, TRB, ATRI

Feb 5 2013 12:47PM