Day, C. M., Stevens, A., Sturdevant, J. R., & Bullock, D. M. (2015). Evaluation of alternative intersections and interchanges: Volume II—Diverging diamond interchange signal timing (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2015/27). West Lafayette, IN: Purdue University. http://dx.doi.org/10.5703/1288284316012
This report presents findings from field studies of operations at diverging diamond interchanges (DDIs) in Salt Lake City, Utah and Fort Wayne, Indiana. These discuss optimization of signal offsets both within the DDI, and with the DDI integrated as part of an arterial corridor. Optimization of Fort Wayne, Indiana corridor comprising the DDI and three neighboring intersections yielded an annualized user benefit of $564,000, when assessing origin-destination paths both along the arterial and for movements to and from the freeway. This is the first field study of DDI offset optimization with neighboring intersections. Additionally, a pilot study was carried out in Salt Lake City on a new phasing scheme that incorporated a “holdback” phase into the signal sequence that delayed vehicles exiting the ramp in order to better coordinate their arrival at the downstream intersection, increasing the percent on green from 53% to 92%. The report concludes with a discussion of practical issues pertaining to DDI signal timing and provides a series of guidelines to assist in the design of new signal timing plans for future DDI deployments.
diverging diamond, signal timing, link pivot offset optimization
Joint Transportation Research Program
Indiana Department of Transportation
West Lafayette, Indiana
Date of this Version