Along the Lakeshore East Line, service will be reduced from every 30 minutes to every hour from Union Station to Oshawa. This is to allow for work to be done at Guildwood station. The reduction of service covers Saturday May 21st, Sunday May 22nd, and Monday May 23rd. Trains will depart Union Station only at 13 minutes past the hour, and 41 minutes past the hour from Oshawa.
Along the Lakeshore West line, regular 30 minute service will continue to operate between Oakville station and Union Station.
However, west of Oakville station, service will be reduced to one train per hour. Trains will depart eastbound from Aldershot only at 1 minute past the hour (the trains at 31 minutes past the hour are cancelled), and westbound from Oakville only at 56 minutes past the hour (the trains at 26 minutes past the hour are cancelled.) This applies to service on Saturday May 21st, Sunday May 22nd, and Monday May 23rd. However, additionally on Friday May 20th, the eastbound trains that normally depart Aldershot at 8:31 pm and 9:31 pm are cancelled, as well as the westbound trains from Oakville that normally depart at 7:13 pm, 8:13 pm, 9:13 pm, 10:13 pm, and 11:13 pm.
The reduced service does not affect the Niagara Falls Excursion train which starts operating this weekend as well.