Complex sentence: It was built as part of the Dual Contracts and jointly operated by the IRT and BMT using IRT-sized cars until 1949, when the platforms were shaved to accept the wider BMT cars and joint service was discontinued.
Split into simpler sentences: It was built as part of the Dual Contracts and jointly operated by the IRT and BMT using IRT-sized cars until 1949. In 1949, the platforms were shaved to accept the wider BMT cars and joint service was discontinued.