This seems to me to be approaching the problem from the wrong end.
If your laundry trough is in danger of running over, you turn off the tap, right? So what if we turn off the tap by making it easier for people to leave their cars at home?
What if we bought some small mini-buses and ran them around the suburbs on a 15-minute circuit. These buses would have a designated circular route but no designated bus stops.
Anyone wanting to board the bus would simply raise his or her hand and board.
The bus would deposit its passengers to the relevant main arterial road to be picked up by ordinary Transperth buses that would run express direct to the station by the shortest possible route while the minibus would recommence its circuit.
The minibuses would run from say 6am to 8.30am and recommence at say 4.30pm to 6pm to collect the returning passengers from the express buses and drop them off where they got on.
Assuming that each minibus was to pick up on average just four passengers per circuit, that equals 16 passengers per hour or 40 per day.
If there were six buses serving say Dawesville-Wannanup, Falcon-Seascapes, Erskine, Mandurah Central and Lakelands-Madora Bay that adds up to 240 people a day.
That’s 240 bays freed right there’