People going to the Derby are being urged to avoid using Epsom station on Saturday as it is undergoing a major redevelopment.
Train operator Southern said travel to Epsom Downs Racecourse from Epsom station will be "extremely difficult" by bus and taxi.
A Southern spokesman said: "Road closures, restricted footpath access and the relocation of bus and taxi pick-up points means that anyone going to the races via Epsom station will find very long waiting times.
"Southern is advising passengers to use either Tattenham Corner or Epsom Downs stations, where onward travel to the racecourse is easier, more convenient and more comprehensive."
A bus service will be running from Tattenham Corner and Epsom Downs stations to the racecourse, but both stations are expected to be more crowded than usual.
Mark Epsom, Southern’s Sutton area manager, said: "We want everyone to have a great day out and have a trouble free journey to and from the racecourse.
"It’s unfortunate that the building works at Epsom station mean that access is severely restricted, but Tattenham Corner and Epsom Downs stations will be more than able to cope with the additional number of passengers expected as a result."