Just to pick up on a term that is becoming common on here. A bus is only withdrawn when its to be disposed from the fleet, or in certain cases buses are stored for operational reasons and are either in reserve or in storage pending further service or pending disposal.

In the case of AV20 the bus is 'under repair' and not withdrawn. There is always a percentage of the fleet off service on long term basis as the repairs needed are too long to fit into planned maintanence/small repairs slots so they are worked on when the man hours/parts are available or they are sent to outside contractors who specialise in these kind of repairs. As Aqua has said many buses have been off service/under repair for long streches. AV167 was off the road for well over 2 years waiting for its roof.