- air scoop
- air stairs
- air-hardened
- aircraft carrier
- aircraft classification
- aircraft effectivity
- aircraft equipment
- aircraft interception
- aircraft light
- aircraft movement
- aircraft tractor
- aircraft tug
- alignment survey
- aground
- aileron control
- air brake
- air circulation
- air corridor
- air supply
- alignment
- alkaline soil
- allocation track
- ambulance coach
- ambulance train
- ambulatory
- anchor pattern
- angle cock
- annealing
- announcement period
- appeals
- approach required
- arbitration bodies
- arc length
- archbar truck
- arrival siding
- assembly pit
- at sight
- archwise connected
- arm rest
- Armco culvert
- articulated stanchion
- assembly dimension
- asphalt revenue
- assembly place
- assignment
- asynchronous flow
- atop
- arrival platform
- arrival station
- assistant driver
- automatic block
- audit
- audit report
- axle seat
- babbitt metal
- bable chain
- bacat ship
- back
- back filler
- back freight
- back shunt
- backing signal
- backup
- backup service
- backup train
- backward flight
- backward takeoff
- axle base
- axle collar
- axle generator
- axle counter
- bad cheque
- bad debt
- bad order
- baffling winds
- bag conveyor
- baggage
- baggage car
- baggage hall
- baggage loader
- baggage retrieval
- baggage terminal
- balance arm
- balance point
- Balance sheet
- balance tab
- balance washer
- balanced aileron
- balanced rudder
- bale loader
- ball bearing
- ballast
- ballast condition
- ballast depth
- ballast drag
- ballast fork
- ballast plow
- ballast pocket
- ballast rake
- ballast residue