- abandoned goods
- abate
- aboard
- acceptance credit
- acceptance trials
- access door
- accessorial service
- accommodation
- accommodation ladder
- accounts payable
- abaft
- abandon ship
- ABC helicopter
- abreast
- aburton
- acceleration detector
- accident detector
- account level
- account paid
- account sales
- accounts receivable
- access
- accessory drive
- accidental braking
- accommodation plan
- accumulator vehicle
- acoustic signal
- actual weight
- actuating plate
- ad valorem
- additional brake
- additional insurance
- additional signal
- administration
- adapter
- additional freight
- additional premium
- adhesion railroad
- adhesion railway
- adhesion system
- adjusting entries
- adjusting potentiometer
- admendment
- admit
- adrift
- advance charge
- advance freight
- advance information
- advance payment
- advance throttle