01518261

Component

Traffic congestion continues to be a serious problem in many cities throughout the United States. One of the biggest causes of long delays at intersections is the heavy demand of through moving and left turning traffic. In order to alleviate the congestion at busy intersections with a high demand of left turning and through moving vehicles, a more efficient intersection design is needed. The Continuous Flow Intersection (CFI) is an at-grade intersection design that can support high-traffic flow where there is a large volume of left turn and through traffic. The CFI is expected to result in better traffic performance compared to a conventional intersection if coordinated and timed correctly. However, previous studies have not considered in depth the optimal signal timings, which are needed in order to achieve fluid progression through the whole 4-legged CFI. This study aims to address this issue by offering a comprehensive analysis of the geometric relationships, signal timing relationships, and fluid progression requirements for a 4-legged CFI through developing a signal timing optimization model. More importantly, due to the different geometric designs between the FHWA and Mexico 4-legged CFIs, this research conducts an analysis to compare these two designs and to see the benefits and disadvantages of these two designs. Microscopic traffic simulation is used in this study to evaluate the two CFI geometric designs with the signal-timing plans suggested by the proposed model. From the analysis it was found that the 4-legged CFI per FHWA design requires longer cycle lengths to achieve the fluid progression condition while the 4-legged CFI per the Mexico standards can achieve fluid progression with smaller cycle length values. The required longer cycle length results in the longer total delay and more stops for the FHWA 4-legged CFI. But the Mexico 4-legged CFI design creates additional traffic conflicts between right-turning traffic and left-turning traffic coming from the opposite approach. This could bring significant congestion when right-turning traffic is large. In addition, this study compares the signal timing determined by Synchro with the one from the proposed model. This simulation results indicate that the proposed models are moderately better than Synchro.

This paper was sponsored by TRB committee AHB65 Operational Effects of Geometrics. Alternate title: Optimal Signal Timing Models for FHWA and Mexican Four-Leg Continuous-Flow Intersections.

01503729

14-5424

English

25p

2014

Transportation Research Board 93rd Annual Meeting

Digital/other

Figures; References; Tables

Four leg intersections; Geometric design; Optimization; Through traffic; Traffic signal timing; Turning traffic

U.S. Federal Highway Administration

Continuous flow intersections

Mexico; United States

Highways; Operations and Traffic Management; I73: Traffic Control

Transportation Research Board Annual Meeting 2014 Paper #14-5424

TRIS, TRB, ATRI

Jan 27 2014 3:54PM