Performance Measures for Optimizing Diverging Interchanges and Outcome Assessment with Drone Video

Abstract

Diverging diamond interchanges (DDIs) are an emerging interchange configuration that eliminates the need for left-turn phases in conventional diamonds and may be less expensive to construct than some alternative geometries. This paper examines signal timing for DDIs. DDI signal timing typically has used a two-phase configuration that reflects the two competing movements at the crossover points at each inter section of the DDI. This configuration inherently contains some inefficiency: (a) there is potential for internal queuing under two-phase configuration and (b) it is possible for the inflow demand to exceed outflow capacity of the interchange. This paper uses high-resolution event data to develop performance measures for evaluating operations at a DDI in Salt Lake City, Utah. Alternatives to the existing signal timing within the two-phase configuration are modeled and tested with a field deployment. The field deployment demonstrated the ability to prioritize ramp or through vehicles within the two-phase configuration. Additionally, a new three-phase configuration was developed and deployed to address the internal queuing that occurs with two-phase timing. With this new configuration, the flows from one DDI intersection to the other are balanced, and progression within the DDI is improved. With the implementation of the three-phase configuration, the percentage of vehicles arriving on green at the heaviest internal movement within the DDI increased from 53% to 92%. To illustrate these performance measures and improved DDI operation qualitatively, a video from a tethered unmanned aerial vehicle demonstrated the vehicle arrival characteristics by overlaying vehicle detection and signal state graphics on the video.

Concurrent Optimization of Cycle Length, Green Splits, and Offsets for the Diverging Diamond Interchange

“…In addition, Day and Bullock ( 11 ) investigated the effectiveness of three different strategies for cycle length for DDI coordination with six different origin–destination (O-D) scenarios through microscopic simulation. The strategies include: (i) the full cycle length of the corridor; (ii) a half-cycle; and (iii) a three-phase scheme proposed by Hainen et al ( 12 ) to manage the queues within a DDI. The measures of effectiveness (MOEs) were the number of stops, movement delays at the DDI, queue lengths, and delay by O-D path.…”

Diverging Diamond Interchange Performance Measures Using Connected Vehicle Data

“…Safety performance has been evaluated from historical crash data to assess improvements compared to other types of interchange and to calibrate crash modification factors [13] [14] [15]. Hainen et al made use of high-resolution event data to assess the internal queuing dynamics and the inflow/outflow demand balance within a DDI [16]. An Automated Traffic Signal Performance Measure (ATSPM) [17] was developed by using traffic signal phase data and point sensors to estimate travel time and arrivals on green (AOG) of vehicle trajectories through the intersection.…”

“…The most critical segment of a DDI is crossover storage. If vehicles in this area fail to be discharged efficiently, delays and saturation at the approaches of the entry crossover could be significantly increased [16]. The crossover storage can receive vehicles from the external street and from the interstate exiting ramps.…”

Use of Microsimulation to Evaluate Signal-Phasing Schemes at Diverging Diamond Interchanges

“…Hu et al tested the optimization of two timing plans, both categorized as three-critical-movement schemes (6). Day and Bullock (7) explored the effect of cycle lengths on two-and three-critical-movement schemes, and Hainen et al (8) compared two-and three-critical-movement schemes on a DDI under real-world conditions.…”