The new TCAM (Traffic Control And Monitoring) data transmission system is now being developed as part of the scheme for modernising urban traffic control (UTC) in London. It also runs a Remote Monitoring System to receive information about equipment faults. TCAM was specified jointly by TCSU and Microsense Systems Ltd, and is a TCP/IP-based open system specification, allowing equipment from different manufacturers to be interfaced to a system. This paper outlines the current state of the TCAM project. TCAM's overall requirements are to: (1) replace obsolescent equipment which is uneconomical to maintain; (2) carry both UTC and monitoring data along the same lines; (3) allow several other tasks to be integrated with UTC and monitoring; (4) be flexible enough to allow parts of the system to be bought from any suitable supplier; and (5) be able to cater for any new traffic control methods when they are introduced. The paper describes the TCAM system architecture and its communications, UTC data transmission, timing requirements, background channels, and leased line bandwidth, priority, and speeds. Before the pilot TCAM system was designed, several data transmission tests were conducted to investigate TCAM's feasibility in general and estimate the expected performance of the overall TCAM-based UTC system.
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