Level 0, Maintenance carried out on a vehicle during operation. Maintenance carried out by a driver or onboard personnel when the vehicle is in service. The maintenance only consists of simple measures to make the vehicle ready for operation.Level 1a, Maintenance carried out on the vehicle on a service track. Comprises on-track maintenance where no lift or pit is available. Maintenance of a removed replacement unit (RE) at a service track is also classified as level 1a.