Early and Late 20th century developments in Traffic Control; two significant periods in UK Signalling history : Peter Bull and Howard Saffer

In every practical application using technical equipment, significant developments in technology create opportunities for major changes in the types of equipment that become available and their use. This paper takes a historical look at the two such changes during the 20th century relating to traffic signal control: the introduction of traffic detection to early electro-mechanical signals; and from solid state controllers to microprocessors.