Engineered Automation & Power Solutions

Traffic Control Application Note

Application Overview

Engineered Software Products has recently implemented a control system for the Kennedy Expressway Reversible Lane and Control (REVLAC) project for the Illinois Department of Transportation. Located on a major interstate highway in downtown Chicago, REVLAC is a system of gated reversible lanes enabling full traffic reversal in less than 30 minutes.

Control of the system is accomplished through an operator panel located at the Illinois Department of Transportation Headquarters 25 miles from the traffic devices. The operator is presented real-time video and status of all devices on the system, enabling quick reaction in the event of an emergency. Special functions allow the operator to accommodate maintenance operations, emergency procedures, and snow plowing.


REVLAC Gate

Application Highlights

  • Programmable logic controller (PLC) control system consisting of five sets of Allen-Bradley redundant PLC5 processors linked by a triple redundant communications subsystem including microwave, dial-line, and UHF modes.
  • Fault-tolerant program design to allow common device failures, such as faulty limit switches, without disabling normal operation of the system. States of devices are cross-checked with other device states to determine proper operation and alarmed when determined to be faulty.
  • Processor redundancy to prevent downtime in case of processor failure. Automatic switchover is accomplished by a seamless transfer of control to the backup processor even during transition periods.
  • User-commanded and automatic video switching subsystem for monitoring transitions and special operations in real-time. Video is recorded for later reference.
  • Automatic voice alarm system capable of contacting appropriate personnel by telephone and pager. A call list is configured for contacting alternate personnel should the desired personnel not acknowledge. The voice message states the type of alarm and the appropriate actions to follow.
  • Historical logging of all I/O and alarm transitions on a centrally located PC. Using a system timestamp, the logged data is displayed using a custom Visual Basic application. The data can be archived as an Microsoft Access database for future reference.
  • Complex testing and documentation methods to facilitate orderly and safe commissioning of the system.
  • Secure remote access to allow remote diagnostics and troubleshooting of system, resulting in significant client savings in time, expense, and downtime.
  • Redundant points of operation at four remote locations.

Application System Architecture


Click the picture for a larger view.

Press and Applications