Traffic Lights

Traffic lights are well understood. Surely they couldn't be described as "bad signs"? 

Consider this scene:

It's Corporation Street in Preston. At the traffic lights the right turn is prohibited. Straight ahead has a blue roundel which bars all except buses, cycles and taxis. The only route out for other traffic is to turn left. 

While all this is obvious from this image, suppose that you are following a double-decker bus. It blocks the view of the advance direction sign which shows that you must turn left. When the lights turn green and you start up, you don't notice that sign and follow the bus to the traffic lights. Here you see that you can't turn right, but the bus obscures the blue roundel ahead. 

The traffic light is an ordinary green light. It gives the message "Go". You do, and get yourself a PCN.

Options for Signal Head Layouts

As well as the familiar three-light forms, others are possible, including those shown below (this diagram is excerpted from Chapter 6 of the Traffic Signs Manual) 

Where the road to the right is restricted to buses and cycles only, the arrangement to the left is used. 

This light turns green a few seconds before the other green lights (full or arrows to left and right). It gives cyclists a few seconds head start before the main traffic flow. The green cycle can be mounted below the full green or to the left of the full green. 

Where 

A similar approach could be used when bus restrictions apply to the road straight ahead. The place for the full green would be filled with a small blue roundel which applied to the road straight ahead. For the green phase, the arrows for turns would come on at the same time as a green bus below the blue roundel in the full green position:

The absence of a full green light in its normal position would indicate to motorists who had missed the earlier signs that they must not proceed straight ahead. The arrows for turns would be the only ones at the third level, indicating that that was where they should go. 

Bus drivers would recognise their symbol on the green bus light. Drivers of taxis, cycles and other vehicles permitted by the blue roundel ahead would see from the blue roundel ahead whether they were permitted. 

Where a left or right turn was controlled by a blue roundel, a green bus would be used instead of the normal green arrow. 

Written 14th November 2025; last updated 14th November 2025