Increasing the Capacity of Signalized Intersections with Dynamic Use of Exit Lanes for Left-Turn Traffic

Abstract

Many congested intersections have a heavy traffic volume on movements for which capacity is insufficient because of geometric limitations. An unconventional approach that increases the capacity of heavily congested intersections is presented: this approach opens up exit lanes for left-turn traffic dynamically with the help of an additional traffic light installed at the median opening (the presignal); this situation is referred to as exit lanes for left-turn (EFL) control. An optimization problem for EFL control was formulated as a mixed-integer nonlinear program, in which the geometric layout, main signal timing, and presignal timing were integrated. The mixed-integer nonlinear program was solved by transformation into a series of mixed-integer linear programs. The latter problem can be solved with the standard branch-and-bound technique. The results of extensive numerical analysis and VISSIM simulation showed that the EFL approach could increase intersection capacity and reduce traffic delay substantially, especially under high left-turn demand. Moreover, the EFL control can be applied to one or multiple legs simultaneously; thus the control is particularly useful for intersections with an unbalanced left demand and a degree of saturation in travel directions.

Increasing Signalized Intersection Capacity with Unconventional Use of Special Width Approach Lanes

“…Some researchers have proposed to use some of the opposing through‐lanes for left turns, which is known as the exit‐lanes for left‐turn (EFL) intersection design (Zhao et al., ). In this strategy, some exit lanes are set as variable lanes.…”

“…However, similar to the DLT intersection, the tandem intersection design requires extra space to hold queues at the presignal. Some researchers have proposed to use some of the opposing through-lanes for left turns, which is known as the exit-lanes for left-turn (EFL) intersection design (Zhao et al, 2013). In this strategy, some exit lanes are set as variable lanes.…”

Driving simulator evaluation of drivers’ response to intersections with dynamic use of exit-lanes for left-turn

“…In practice, the location of the median opening should be optimized according to the traffic demand pattern and the geometric characteristics of the intersection (Zhao et al, 2013), while in this experiment, for fair comparison, all the locations of the median opening are 50 m before the intersection stop line. The width of the median is set to be 1.5 m as the minimum value specified in the code for design of Fig.…”

“…One of these innovative intersection designs, as shown in Fig. 1, is to use some of the opposing through-lanes for left turns, which is known as the exitlanes for left-turn (EFL) intersection design (Zhao et al, 2013).…”

“…In an earlier study (Zhao et al, 2013), an optimization model for the EFL control has been formulated, in which the geometric layout, main-signal timing and pre-signal timing were integrated. The EFL control could increase the capacity of an intersection with promising preliminary results especially under high left-turn demand compared with conventional intersection control.…”