ATAC Develops Traffic Technology
A solution to this problem is to use an actual traffic signal controller as part of the simulation, a process known as hardware-in-the-loop simulation. The Federal Highway Administration led development work for a hardwarein-the-loop platform for its CORSIM traffic simulation model in the mid to late 1990s. As a result, a controller interface device (CID) was developed at the University of Idaho. Using the CID, emulated traffic signal control logic is replaced by actual traffic controller hardware in the simulation model. This ensures accurate results from the simulation and enables the use of controller-specific functions not available in traffic software simulation models. ATAC has been developing a CID that would improve existing technologies and work in conjunction with the VISSIM traffic simulation model. The effort which began in 2001 as a senior design project for electrical engineering students is now complete. Throughout the development, ATAC researchers and students strived to control product cost and improve performance. Therefore, the focus was on using off-the-shelf technology in building the CID. The Controller Interface Software (CIDserv) resides and runs on the CID itself and responds to the traffic controller. It logs frames that the controller sends out over its SDLC channel. It then formulates a response based on information from the VISSIM Interface Software module. This will keep the controller out of "flash mode" and keeps the detector and signal states synchronized between the simulation and controller. This software can be upgraded over the Internet using FTP software built into the program. The CID uses standard SDLC communications with the controller and Ethernet for Internet connectivity with the simulation software. That makes ATAC's CID unique since it can be networked through the Internet. Therefore, a simulation project can use resources (CID-controller combinations) from several locations throughout the world, creating a virtual traffic lab. ATAC has built and tested four CID prototypes which are being used on various research projects. Although marketing of the CID has not officially begun, it is currently available for other agencies or companies to purchase or use. Except for equipment ordering lead time, the CID may be assembled and tested in a matter of hours. For more information about the CID please visit www.atacenter.org/cid/. |
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With the continued surges in traffic levels, especially in urban areas, more and more traffic engineers are taking advantage of modeling tools to help optimize system operations. Traffic simulation software models are among the most powerful tools that can analyze complex traffic scenarios, evaluate alternatives, and estimate impacts of traffic control strategies. However, for some of the more advanced traffic signal control applications, traffic simulation software may not be able to adequately model traffic control system hardware behavior. In other words, the software logic approximates the functions of the traffic signal controller.