Traffic Analysis Tools Program
photo of traffic traveling in both directions on a congested highway
21st Century Operations Using 21st Century Technologies

Corridor Simulation (CORSIM/TSIS)

The Traffic Software Integrated System (TSIS) is a collection of software tools for use by traffic engineers and researchers. Originally built as a simple shell around CORSIM, TSIS has evolved into a sophisticated toolkit. Though used by the FHWA for conducting research, these tools are sold to the public.

CORSIM is a comprehensive microscopic traffic simulation, applicable to surface streets, freeways, and integrated networks with a complete selection of control devices (i.e., stop/yield sign, traffic signals, and ramp metering). It simulates traffic and traffic control systems using commonly accepted vehicle and driver behavior models. CORSIM combines two of the most widely used traffic simulation models, NETSIM for surface streets, and FRESIM for freeways. CORSIM has been applied by thousands of practitioners and researchers worldwide over the past 30 years and embodies a wealth of experience and maturity.

CORSIM has expanded the capabilities of NETSIM and FRESIM with the following major enhancements:

  • HOV Lanes in FRESIM
    Some of the features of HOV lanes are:
    • HOV lane bypass at ramp meters is allowed.
    • Incidents can occur on HOV lanes.
    • An HOV lane can be dropped using Record Type 32. A lane can be added using Record Type 32 and specified as an HOV lane using Record Type 33.
    • Full-length auxiliary lanes can be specified as HOV lanes.
  • Freeway Ramp Metering
    A multiple occupancy threshold algorithm and an ALINEA algorithm are introduced. In addition, in the fixed-time ramp metering, logic allowing two vehicles per green is implemented.
  • Vehicle-Type-Specific Turn Percentages
    Surface street turn movement percentages and freeway exit percentages can be manipulated by vehicle type. This is useful for modeling facilities such weigh stations, toll booths, airport loading/unloading zones or anywhere that control of specific vehicle types is desired. Record Type 24 was added to introduce the concept of Vehicle-Type-Specific Multipliers for Fresim in version 4.32, and was added to Netsim in version 5.0.
  • Support Larger Networks:
    Many of the data arrays within CORSIM that previously were allocated statically using predetermined sizes, or limitations, are now being allocated dynamically using the correct size required for the network. That allows CORSIM to simulate much larger networks and it also makes the size of the CORSIM executable file much smaller when simulating smaller networks.
    • Increased maximum network size to the maximum allowed using the CORSIM node numbering scheme. Node numbers 1 through 6999 can be used for internal nodes. Node numbers 7000 through 7999 can be used for interface nodes and node numbers 8000 through 8999 can be used for entry or exit nodes. There is no limit to the number of links, segments or vehicles, other than the limitations imposed by the amount of available memory on the computer that is running CORSIM.
  • Path Following Capability:
    Vehicles normally follow paths that are determined randomly based on turn percentages, but CORSIM allows the user to define specific paths and force vehicles to follow those paths. The path following capability was added to CORSIM for use in a study performed for FHWA and was not designed for ease of use or for flexibility.

For information on ordering CORSIM/TSIS.

Office of Operations