The City of Louisville
Department of Public Works

Traffic Engineering Division

The City of Louisville, Kentucky is implementing a new advanced traffic signal system. The traffic control system has been designed to bring approximately 580 remote signalized intersections under a central computer control.

Engineers at The City of Louisville D.P.W. is using fiber optic communications for a portion of the project in addition to the use of copper pairs. The fiber optics are being used as the transmission medium for the data being communicated from the signalized intersections back to the Central Computer System in the control center, which is located in the lower level of City Hall.

RFL Electronics Inc. has been playing a very important role in the deployment of the communications system. Louisville required a T1 Multiplexer which was capable of communicating RS-232 data over fiber optics from the Type-170 traffic signal controllers, as well as being able to survive in the harsh conditions present in an outdoor cabinet enclosure. The Multiplexer chosen for this application was the RFL IMUX-2000. The IMUX 2000 is designed for harsh environments and has a wide temperature range of -20° C to +55° C. It meets the IEEE/ANSI standards C.37.90-1989,C.37.90.1 and C.37.90.2 for Fast Transient and EMI. It is also UL and FCC approved. The IMUX 2000 has a wide range of Voice and Data channel interfaces to satisfy most communications requirements.

The diagram alone depicts the RFL IMUX 2000 as it fits into the traffic signal scheme. In this application, the multiplexers were configured in a point to point terminal end configuration. Each IMUX was fitted with several DA-191A asynchronous data channel modules. These channel modules are a four channel design for use in terminal end and or drop/insert multiplexers. The module provides transmission of one to four asynchronous data channels over one DSO in a T1 or E1. The maximum data rate is 19.2 kbps for one or two channel operation, and 9.6 kbps for four channel operation. The DA-191A requires a module adapter on the rear of the Multiplexer chassis which has four DB-9 RS-232 ports for communication.

In the first phase of the project, three multiplexers were placed in strategic locations in downtown Louisville. Copper pairs emanate from the Multiplexer cabinet site out to many different intersection locations. The traffic signal data is transmitted and received via modem over copper pairs to the Multiplexer. This is where the data is concentrated and then communicated to the head-end Multiplexer at City Hall. The RS-232 data is taken off the IMUX and then fed to the central computer system.

The IMUX 2000 system is equipped with the ultimate Network Management System which operates in a Windows™ point-and-click environment. This will provide Louisville D.P.W. personnel network visibility from any node and allow for remote provisioning, monitoring and alarm reporting which can help minimize any unnecessary field service calls.