Ramp Meters Evaluation: Using ITS Archived Data

Abstract

In December 2009, ramp meters along US 95 in Las Vegas between Rancho Drive and Craig Road were activated. A study was performed to quantify the benefits of ramp meters on the freeway mainline by using archived ITS data. Traditional performance measures such as average travel speed, speed standard deviation, interquartile speed range, travel time index (TTI), and buffer index (BI) were employed to conduct the evaluation. In addition, two new performance measures—delay volume (DV) and average vehicle delay (AVD)—developed by the Freeway and Arterial System of Transportation (FAST) Division of the Regional Transportation Commission (RTC) of Southern Nevada were used to enhance the evaluation. Specifically, DV quantifies the congestion with temporal, spatial, and congestion intensity values, and AVD measures the average delay per vehicle with traffic volume as a weighting factor. Comparing both the freeway and ramp performance with and without ramp meters clearly demonstrates that ramp meters are very effective in mitigating the recurring heavy congestion for southbound US 95 during weekday peak periods. The improvement is comparatively little on the more lightly congested northbound section of US 95. The evaluation results also demonstrate that the DV and AVD metrics are useful in evaluating operational strategies such as ramp metering. Finally, informative results are achieved regarding the influence of ramp meters on the bottleneck, and the comparative effects metering has on the general purpose and high occupancy vehicle (HOV) lanes.