Transit advocate and Women's Post publisher Sarah Thomson officially joined the Toronto mayoral race on Thursday morning.

She rode up to city hall in a horse-drawn carriage at 8:30 a.m., speaking with reporters before entering the building to file her paperwork.

Thomson ran for mayor in 2010, but pulled out of the race early, putting her endorsement behind George Smitherman. The next year, she ran for the Ontario Liberals in the riding of Trinity-Spadina, coming in second.

Since then, Thompson said she’s been "studying the city and working on solutions."

Talking to reporters Thursday, she said, "What I found is we need a new process at city hall. We don't have the right systems in place."

Thomson also said she's focusing on building subway extensions that are subsidized by tolls on the Gardiner Expressway and Don Valley Parkway that will apply only to drivers who don’t live in the city.

"I don't think there's anybody out there that's going to push as hard or care as much for the transit expansion as I do," Thomson said after filing her papers at city hall.

Her online platform also lists suggestions for electoral reform, business growth, social housing and funding for the arts.

"I'm running because I believe I can do the job," she said.

"City hall needs change, and I want to be that change to city hall. It's about real ideas and real solutions."

Thomson joins a slate of approximately 40 candidates that includes former NDP MP Olivia Chow, former Ontario Progressive Conservative Party leader John Tory, former Toronto Transit Commission chair Karen Stintz and former city councillor David Soknacki. A full list of candidates is available online.