The inter-regional transit system decided to expand Quiet Zones after rolling it out successfully for the Barrie line in February.
Under the rules, the top level of trains will be designated as areas where customers can squeeze in a nap.
Quiet Zone passengers would be expected to silence their mobile devices and to only have "short and quiet conversations" or speak in brief, hushed voices if their phones ring, GO Transit said in a statement.
Otherwise, people may take their conversations downstairs to a lower level.
The bottom two levels will remain open for passengers who wish to be social while they travel.
Quiet Zone periods will be in effect Monday to Friday, between 6-9:30 a.m. and 3-7:30 p.m. for trains arriving at or departing from Union Station.
The pilot will begin July 15, but there is no set end date for the project. Go Transit will continue to gather feedback from its customers.
Passengers on the Barrie line were overwhelmingly in favour of the Quiet Zone experience, with 83 per cent saying the new zones made their trips more comfortable.