A vehicle occupying a lift for two days, not being worked on

Bays are the constraint in most service centres. Everything that occupies one without producing work is directly reducing capacity.

Starting before checking

Jobs frequently begin before anyone confirms the required parts are on hand, because the requirement is only known once work starts. That is real, and it argues for stocking decisions rather than for a process rule.

Occupancy is not utilisation

A centre reporting full bays may be reporting stationary vehicles. Separating the two is the difference between believing you need more space and knowing you need better parts availability.

Stock the common failures

Job history shows which parts recur. Centres frequently find that a small number of items account for most parts-related delays, and that stocking them costs less than the capacity they consume.