Rail Traffic Flow Analysis to Reduce Congestion

The Assignment

Union Pacific operates the largest railroad in North America.

The level of traffic congestion in the LA Basin was becoming a major concern. Traffic flow was adversely affected by the volume of inbound and outbound trains across a rail network that was mainly comprised of single track segments. Sharing track with local transit authorities and other trains further degraded the potential velocity of UP trains flowing across this rail system.

To help Union Pacific better understand the issues affecting the rail system, Visual8 developed a Rail Traffic Flow Analysis simulation tool to analyze Union Pacific’s train flow and operations in the LA Basin under various scenarios.

The Solution

The simulation tool was developed using SIMUL8 Simulation software and modelled the existing LA Basin rail system with a network of track segments and yard definitions. This rail network managed the flow of inbound and outbound trains using priority rules and meet/pass logic to regulate traffic on single-track segments. The model logic includes rules governing traffic flow such as train meet/pass rules taking into account immediate and approaching train priorities, siding locations and track segment conditions.

Inputs into the simulation included:

  • Inbound train volumes by type, time of day, and day of the week;
  • Scheduled Hauler departure times from the main yard to satellite yards; and
  • Outbound train schedules from the main yards to various destinations.

Train characteristics including routing information, running speeds, lengths and priorities; as well as track segment information defining mile points, rail type (single/double), track lengths, connections, siding locations, track speeds, and crew changes could also be changed within the model.

  • The average and maximum number of trains on sidings at any given point in time,
  • The number of trains waiting to get clearance,
  • The length of time required to obtain a clearance,
  • The time necessary for a hauler to travel between satellite yards, and
  • the number of instances in which a train traveling to a particular destination has taken longer than a specified threshold value.

The Results

The simulation model assessed current conditions and identified cost-efficient measures to improve train flow across the LA basin. This ranged from modifying inbound and outbound train schedules to minimize track congestion and train delays, to the more expensive option of introducing additional sidings and/or double-track on certain main line segments.

The Rail Traffic Flow Analysis tool allowed the company’s operations team to effectively and accurately:

  • Conduct traffic flow analysis,
  • Measure the effects of system changes such as outbound train schedules, and
  • Evaluate alternative system design configurations.

Ultimately, the simulation tool helped Union Pacific’s determine a number of cost effective solutions to alleviate current and potential future train congestion issues for their LA Basin operations.