Longtime BART Board Director Tom Radulovich will not seek re-election in November.

Radulovich, who made the announcement Monday in a Facebook post, said leaving the board would give him more time to focus on Livable City, the organization he heads. He was first elected to the BART Board of Directors in 1996 and represents the 9th district, which includes about 40 percent of San Francisco, including the Mission District, Castro District, the Haight and Hayes Valley. The BART Board of Directors is made up of nine district directors.

“Basically every four years when it’s time to run I ask myself ‘do I want to do this for another four years?’ This time I came up with a different answer,” he said.

As a director, Radulovich has advocated for “the reinvestment and renovation of the BART system, and improving BART practices in the areas of sustainability, accessibility, customer service, architecture and urban design, and the creation of transit villages at BART stations,” he wrote in his announcement.

At Livable City, Radulovich said he will continue to advocate for the same goals he did as a BART director: making the Bay Area a better place for public transit, walking, and biking. Livable City helps run San Francisco’s popular Sunday Streets program, where neighborhood corridors are closed off to automobile traffic for the day.

“There are not a lot of things that I do at my day job that are not closely aligned with what I have been doing as a BART director,” he said.

Radulovich has endorsed Lisa Feldstein, a faculty member in the public affairs program at the University of San Francisco who previously served as a city planning commissioner. Activist Michael Petrelis, a frequent candidate for public office, has also taken out papers to run for the seat.

J.K. Dineen is a San Francisco Chronicle staff writer. Email: jdineen@sfchronicle.com Twitter: @sfjkdineen