Thousands of Sydney rail passengers will be forced to switch trains at the already overcrowded Central Station during peak hours after the closure of the Epping-to-Chatswood line next month.

Internal government documents, obtained by the Herald, show more peak-hour trains running from and to Hornsby in Sydney's north will terminate and start at Central Station.

Thousands of passengers will be forced to change trains at Central. Credit:James Alcock

It means that during the morning peak a greater number of passengers will be forced to get off to catch other services to central-city stations such as Town Hall and Wynyard.

The documents reveal one of the challenges for rail staff will be managing extra crowds at Central – especially in the Olympic Tunnel at the northern end – due to more people switching services.