New commuter rail lines may need to be built on the busiest routes into London in coming decades as capacity on existing lines is exhausted, the rail industry has warned in a joint report on its future needs.

New lines are likely to be necessary as railways creak under the strain of a doubling of passenger and freight demand in the next 30 years, says the Planning Ahead document, compiled by Network Rail, the Association of Train Operating Companies and the Association of Freight Operators.