§ Lord Methuen
asked Her Majesty's Government:
Whether they have plans to introduce road traffic signals (as used elsewhere in Europe) which display an additional numeric aspect in red or green as appropriate to that phase of their operation, indicating the number of seconds remaining for that phase. [HL 3464]
§ Lord Davies of Oldham
Many countries operate traffic light signals with fixed green and fixed red periods. In these circumstances, countdown timers can be used as the remaining period is known precisely.
In the UK, the majority of traffic signals are vehicle-actuated, the duration of the green period being affected by the vehicular flow on that approach and the demand from any opposing flow or pedestrian push buttons. Typically, the green period could vary between 7 and 30 seconds during the working day. At quieter times the green will stay illuminated until a demand is registered from an opposing approach or push button.
This responsive system has advantages in terms of efficient vehicle flow and fuel economy. It also minimises frustration caused by unnecessary delays, as drivers and other road users can normally see the need for being held on a red signal. With this system, countdown timers are not a practical proposition, as it is impossible to predict the green time left.