CORSIM™ Run Time Extension
TSIS is an integrated development environment that enables users to conduct traffic operations analysis. Built using a component architecture, TSIS is a toolbox that contains tools that allow the user to define and manage traffic analysis projects, define traffic networks and create inputs for traffic simulation analysis, execute traffic simulation models, and interpret the results of those models. Although it comes pre-configured with a set of tools, TSIS provides a mechanism by which an external application can interface directly with CORSIM simulation. This type of application has become known as a CORSIM run-time extension (RTE). Run-time extensions can be built to replace existing logic in CORSIM, or to supplement the logic. The original run-time extensions were tailored for signal timing studies. However, the concept has been expanded to support freeway monitoring, incident detection and ramp metering run-time extension packages.
The RTE capability enables CORSIM to operate with actual hardware in the loop. Some examples of these hardware-in-the-loop experiments include using 170, NEMA, and 2070 controllers to control the signal states at certain intersections in the simulation. The controller is interfaced to the simulation using the Controller Interface Device (CID) developed by Louisiana State University under the direction of FHWA. Another experiment involved using an advanced camera sensor and image processing software to estimate the queue state of simulated vehicles as they approach an intersection. Queue states for intersection approaches are used by an adaptive control algorithm to make intelligent decisions about what the optimal signal state should be. Run-time extensions can also be used to test adaptive signal control algorithms for effectiveness before they are implemented in the field. With the rapid evolution of technology, these types of experiments are necessary not only to assess the benefits of advanced ITS applications, but to verify their operational capability before field deployment.
In TSIS 6, the RTE can now access CORSIM at additional processing control points, providing more control to an RTE and allowing a wider variety of extensions to CORSIM. New actuated control API functions enable RTE developers to access critical control parameters and obtain diagnostic state information regarding actuated control. RTEs developed for versions prior to version 6.1 may need to be modified if they access detector data, which is now dynamically allocated and must be imported differently. The sample RTE included within TSIS demonstrates the new method of importing detector arrays.
A new API function is now available to execute NETSIM actuated signal logic, giving RTE developers an easy way to operate actuated signals without having to duplicate logic in the RTE. New API functions also allow switching to, and from, a pre-specified alternate actuated control timing plan. These functions allow for a more advanced simulation of actuated signal pre-emption, when compared to the simple pre-emption method used by CORSIM when RTE’s are not involved.