The Public Transport Authority has begun surveying train commuters at stations along the Mandurah Line to understand the potential impacts of a month-long train shutdown.
Mandurah-Perth commuters are bracing for the service disruption, which will be the longest in Perth history.
The Mandurah line - which services 60,000 journeys-a-day - will be partially closed for up to 25 days in late December to allow for construction work on the Metronet Thornlie-Cockburn Link.
The line will close completely between Aubin Grove Station and Elizabeth Quay Station and operate at a reduced capacity between Mandurah Station and Aubin Grove Station.
Surveying began this week, as the PTA determines how to best target the bus replacement capacity and how to best communicate the blockade travel options with passengers.
"We want to hear from people about the disruption and how we can minimise impacts on their travel," Transport minister Rita Saffioti said.
Ms Saffioti said it the shutdown be the biggest disruption of the public transport network Perth has seen and commuters would have to find an alternative route into the CBD.
"We know that this shutdown will be disruptive and inconvenient for many people and we apologise in advance for this."
"So (taking annual leave) will be a personal choice of commuters. But we also understand that people sometimes can't do that. What we're asking of people in the southern suburbs is to plan ahead. We don't want to choke the freeways."Transport Minister Rita Saffioti
She backed down from comments made to The Sunday Times on the weekend, which encouraged commuters to take annual leave or work from home to ease the expected congestion on the roads.
"We encourage everyone who may be impacted to start thinking about what they may be able to do to make travel throughout this period easier, such as catching the Armadale train line, using a rail replacement bus or even looking to see if you can take annual leave or work from home," Ms Saffioti said.
At a media conference on Sunday she said the leave option was a "personal choice" and should be seen as "a last resort".
"So (taking annual leave) will be a personal choice of commuters. But we also understand that people sometimes can't do that. What we're asking of people in the southern suburbs is to plan ahead. We don't want to choke the freeways."