Capacity and Cost Benefits of Super 2 Corridors

Super 2 corridors with passing lanes provide operational benefits to traditional two-lane highways by creating passing opportunities and reducing delay and crashes, leading to increased use of Super 2 corridors across Texas. However, as more passing lane length is added to a Super 2 corridor, the more it may resemble a traditional four-lane alignment and reduce the unique benefits of a Super 2 treatment. This project investigated the operational and economic benefits of Super 2 corridors compared to traditional four-lane and two-lane cross-sections. Researchers analyzed the operational performance of a simulated 40-mile corridor with varying average daily traffic (ADT); heavy vehicle volumes; length, number, and spacing of passing lanes; and access to identify operational benefits in key scenarios. Operational and benefit-cost inputs formed the basis of a model to quantify the relative economic benefits of Super 2 corridors. Operational analysis showed that, at volumes up to 17,000 vehicles per day, Super 2 cross-sections provided higher average minimum speeds and lower delay than other options with less than four lanes, though the two-lane cross-section with left-turn lanes had similar performance as Super 2 for volumes of 15,000 vehicles per day or higher. The cross-section with left-turn lanes was more stable at the highest volumes, suggesting that as volume and truck percentage increase, accommodating turning vehicles outside the through lane can improve operations more than an additional through lane or a passing lane. The economic analysis showed that Super 2 had the highest benefit-cost ratios in all ADT and truck percentage configurations, and they had the best net present value in most cases. In both the economic and operational analyses, the findings agreed with previous research that adding shorter passing lanes to a Super 2 corridor is more beneficial than providing fewer but longer passing lanes.