YOUR Walmgate Bar traffic chaos story (June 27) highlights the key contribution signals make to the safety of the travelling public and their ability to get around.

People are quick to criticise when signals hold them up or do not change as quickly as they would like. I often get demands to switch signals off from people who are convinced this will improve their journey. It is incidents such as this that serve to remind us all that like them or not, signals are vital.

The Walmgate fault was caused because the internal device (known as a watchdog) that constantly monitors how the controller is operating thought it saw a conflict, which would have allowed a green signal to be shown simultaneously to opposing movements.

Following its programme it immediately shut down the whole system. The delay in getting the signals working again was caused by the thorough checks that we had to carry out to make sure this apparent conflict was not real.

Peter Evely,

Head of highway regulation,

City of York Council,

St Leonard's Place, York.

Updated: 11:01 Friday, June 29, 2001