B Train may refer to the following rail transit terms:

• The B (New York City Subway service) in New York City
• The Green Line "B" Branch in Boston, Massachusetts
• Road trains are also sometimes called B-trains

In the simplest terms a B-Train (as related to the road transport or trucking industry) consists of two trailers linked together by a fifth wheel, and are up to 26 m (85 ft) long. The fifth wheel coupling is located at the rear of the lead, or first, trailer and is mounted on a "tail" section commonly located immediately above the lead trailer axles. In North America this area of the lead trailer is often referred to as the "bridge". The twin-trailer assembly is hooked up to a tractor unit via the tractor unit's fifth wheel in the customary manner.

B Train may refer to the following rail transit terms:

• The B (New York City Subway service) in New York City
• The Green Line "B" Branch in Boston, Massachusetts
• Road trains are also sometimes called B-trains

In the simplest terms a B-Train (as related to the road transport or trucking industry) consists of two trailers linked together by a fifth wheel, and are up to 26 m (85 ft) long. The fifth wheel coupling is located at the rear of the lead, or first, trailer and is mounted on a "tail" section commonly located immediately above the lead trailer axles. In North America this area of the lead trailer is often referred to as the "bridge". The twin-trailer assembly is hooked up to a tractor unit via the tractor unit's fifth wheel in the customary manner.