Articles with means of transport and transport-related expressions.
Use the zero article after by when referring to a means of transport.
Use by bus, by train, by car, by taxi, by plane, by bicycle and by boat when describing how someone travels rather than referring to a particular vehicle.
Use a/an or the when referring to a particular vehicle.
Compare "We travelled by train." and "We caught the train at 8:00." The first describes the means of transport, while the second refers to a specific train.
Use the before a specific bus, train, plane, ship or other vehicle after get on or get off.
Examples include get on the bus, get off the train and board the plane.
Use in with cars and taxis, and on with buses, trains, planes and ships.
Examples include in the car, in a taxi, on the bus, on the train and on the plane.
Use on foot when travelling by walking.
English uses the fixed expression on foot rather than by foot.
The choice of article depends on whether the vehicle is mentioned as a means of transport or as a specific object.
Compare "She came by bus.", "She took a bus." and "She took the bus that stops outside her house."
Many transport expressions use a fixed article pattern.
Examples include by air, by sea, by rail, by road, take a taxi, catch a bus, miss the train and board the plane.
Do not use an article after by when naming a means of transport.
Incorrect: by the bus, by a train. Correct: by bus, by train. Use an article only when referring to a specific vehicle.