Coaches are being laid on to help supporters get to and from Twickenham Stadium for Army v Navy matches.
A strike by the RMT union on May 13 is threatening to affect the crowds at the UK's biggest amateur sports event.
Trains to Twickenham station are severely reduced on the day and the station closes at 6.30pm.
The men kick off at 2pm, followed by the women's match which is expected to end around the same time as the station closes.
Buses will be available before and after the matches to shuttle fans to Hounslow and Richmond Underground stations.
The Tube network remains open.
Additional car parking has been added at the stadium for the day. Parking detail is available here:
Organisers asked supporters to consider driving, sharing cars or hiring coaches and using the car parks.
There are no train services beyond Staines to Ascot and Reading all day.
Forces News and BFBS will be broadcasting both matches live and for free on Forces News YouTube channel and BFBS TV for serving personnel.
The additional measures announced:
There will be a core service of two trains per hour into Twickenham Railway Station from Waterloo up to 18:30.
Between 11:10 and 13:35 a total of 14 trains will run from Waterloo to Twickenham.
Two trains per hour from Windsor & Eton Riverside to Twickenham. There is no train service beyond Staines to Ascot and Reading all day.
20 RFU shuttle buses from both Hounslow and Richmond to link up with London Underground and Overground services.
Additional car parking
Please note that the women’s match KO is 16:45 with an approximate finish time between 18:20-30.
A total of 18 trains between 15:45 and 18:30 from Twickenham Train Station to Waterloo. At 18:30 Twickenham Rail Station will close, to assist with this bars will close at 17.30.
Two trains per hour from Twickenham to Windsor & Eton Riverside until 18:30.
20 RFU shuttle buses to both Hounslow and Richmond to link up with London Underground and Overground services.
More details on the matches are available here
Watch the match live on Forces News YouTube channel and BFBS TV from 1330.