Analyzing the Incremental Transition from Single to Double Track Railway Lines

Long term demand for rail freight transportation in North America is projected to increase considerably in the coming decades. Additionally, government agencies want to increase the speed and frequency of passenger trains operating on certain freight lines, further adding to demand for new capacity. A significant portion of the routes in the United States are single track with passing sidings. As traffic increases, additional trackage will be necessary to maintain network fluidity. Incremental additions to infrastructure should be placed to match traffic growth. The most likely approach will be addition of a second main track along portions of a route. This second track can be phased in over time creating hybrid track configurations. As the second track is installed, the operation will transition from single-track characteristics to double-track characteristics. Rail Traffic Controller (RTC) was used to simulate various hybrid track configuration under different operating conditions. In addition to the amount of second main track added, the analysis considered the interaction of traffic volume, traffic composition, and speed differential between train types. Adding sections of double track reduces train delay linearly under constant volume. Because of this linear relationship in delay, capacity will have a convex transition function from single to double track. These results will facilitate the development of an optimal incremental upgrade model for capacity expansion.