The Road Traffic (Traffic and Parking) (Amendment) (No. 2) Regulations 2012 permit taxis in the course of business to use normal (with-flow) bus lanes.
When Can a Taxi Use a Bus Lane?
A taxi can use a normal (with-flow) bus lane only while it is operating as an SPSV – carrying a passenger, on the way to pick up a pre-booked customer, or plying for hire. Taxis must not use bus lanes if they are not operating as an SPSV – for example, driving home at the end of a shift, travelling on personal business, or transporting only goods and not passengers.
Taxis are not allowed to use contra-flow bus lanes (in which traffic travels in the opposite direction to the traffic beside it) under any circumstances.
Hackneys and limousines are not permitted to use bus lanes.