Incremental Capacity in Transitioning from Double to Triple Track on Shared Rail Corridors

The North American freight railroad network is projected to experience rising transportation demand in the coming decades, leading to increased congestion on many rail lines. Capacity is further strained by increased interest in increasing the speed and frequency of passenger service on shared rail corridors. Since passenger trains in North America predominantly operate on corridors where freight railroads own the track infrastructure and are responsible for train dispatching and control, continued hybridization of these freight rail lines by introducing passenger train operations jeopardizes operational fluidity of the network. Capacity loss due to heterogeneity between passenger and freight operations is particularly critical in the North American context since the majority of mainline corridors are single-track with passing sidings or with short segments of double-track. These track arrangements lack the flexibility to handle dense traffic composed of multiple train types. Increasing capacity through triple-track installation, however, requires significant capital investment, right-of-way, and environmental permitting, and so the third main track must be allocated along a line in an optimal manner to provide maximum return on investment. The research presented in this study seeks to characterize the relationship between incremental line-capacity and the phased transition from double to triple track. Results suggest a linear relationship between train delay and percent triple-track installed, regardless of crossover arrangement. While railroads must consider many factors in selecting capital expansion projects, the guidelines presented here can streamline the decision process by helping to quickly identify projects with the most potential for more detailed engineering evaluation.