Balancing the Service Benefits and Mainline Delay Disbenefits of Operating Shorter Freight Trains

Abstract

Advanced train control systems enabling single-person crews or driverless trains promise to significantly reduce the fixed costs of operating a train, removing a strong incentive for longer trains. For carload freight traffic, operating a given number of railcars in shorter trains enables railroads to improve service quality and revenue through increased train frequencies or more direct trains bypassing intermediate classification yards. However, operating shorter trains increases the total number of trains on existing rail corridors, exacerbating congestion and decreasing network fluidity. Rail Traffic Controller simulation software is used to quantify the potential mainline delay impacts and relative capacity consumption of shorter trains. Different combinations of train length and train type heterogeneity are tested on representative single-track freight corridors. Results indicate that train control systems with moving blocks can mitigate some of the mainline delay impacts of shorter trains, particularly at a high traffic volume, with a mix of train types and a greater proportion of railcars traveling on short trains. Mid-siding crossovers can further boost the effectiveness of moving blocks in managing complex train conflicts caused by train type heterogeneity. Simulation results are used to perform an example railcar transit time estimation illustrating the trade-off between yard connection time benefits and mainline delay disbenefits, and the thresholds at which different operating strategies produce a net transit time benefit. Understanding the mainline delay impacts of shorter trains can assist railroad practitioners formulating long-term capital investment plans, developing future operating strategies, and improving service quality and market share through a short train philosophy.