Bus lanes are a common sight on city roads now, and knowing when to use them, and when not to is essential. As well as being liable to a fine for using a bus lane when in operation you can fail the driving test; you can also fail the test for not using it when it is out of operation.
Bus lane signs and markings
The start of a bus lane is marked by a thick broken white line, and accompanied by a sign showing the times of operation of the lane. There may also be right deflection arrows marked on the road before the start of the lane, emphasizing the need to change lanes; these arrows only apply during the bus lane times of operation.
The blue sign indicates which type of vehicles if any besides buses may use the lane. In this example, the sign indicates the bus lane may also be used by motorcycles, cyclists and taxis. The days and times the lane is in operation will also be displayed. If no days are specified then the times apply everyday.
There may be two times displayed indicating separate morning and afternoon periods.
If no time is specified then the bus lane is in operation twenty four hours. A sign may also specify 24 Hour.
An official explanation of the enforcement of bus lanes and when it is legal to enter an active bus lane can be found here:
https://www.nidirect.gov.uk/articles/enforcement-bus-lanes-and-bus-only-streets