Richard Riordan grumbled to two other former Los Angeles mayors on Thursday about the traffic clogging his Brentwood neighborhood. “How long does it take to get to downtown L.A. to go to the theater at night?” he asked.

“If you take the subway, it will take about 25 minutes,” Antonio Villaraigosa joked, recalling his thwarted ambition to build a “subway to the sea.”

James K. Hahn, who moved to Santa Monica after leaving office, recommended the Expo Line: “That’s the way to go, Dick. Don’t take your car.”

The three former L.A. mayors gathered on a UCLA stage Thursday night to share thoughts on running the city. Together, their terms spanned two decades marked by the Northridge earthquake, the San Fernando Valley’s threatened secession from L.A., and an economic crash that left city leaders struggling to stave off bankruptcy.

Their rivalries have subsided, allowing for a candid conversation as part of UCLA’s “Why History Matters” presentations. Some of it was personal. Riordan, 86, revealed his plans to remarry this weekend. His fiancée is Elizabeth Gregory, the director of admissions at Harvard-Westlake School in Studio City.

But the former mayors focused mostly on the city. Villaraigosa, 64, called for a huge expansion of the mayor’s power. The city and county governments should be consolidated under the mayor, along with the public school system, he argued.

“You need a strong key executive,” Villaraigosa, now a candidate for governor, told the audience of a few hundred people.

Hahn rejected the idea of expanding the mayor’s power, saying the city works pretty well. “I don’t think you need to have a czar,” he said.

Riordan applauded Villaraigosa’s failed attempt to put the L.A. Unified School District under the mayor’s control, but Hahn suggested it was a bad idea. “At some point, you load too much on one person,” he said.

At a time when President Trump is threatening to deny federal money to cities like L.A. that limit cooperation on immigration enforcement, Hahn and Villaraigosa, both Democrats, said the city needs to make sure that crime victims and witnesses can talk to police without fear of deportation.

But Riordan, a Republican, said the policy, which dates to 1979, has never worked because major criminals who were in the U.S. illegally were sometimes released from jail rather than deported.

Riordan bemoaned rising pension costs for retired city workers.

“It’s dramatically gone up since Jim and I were mayor,” he said in a dig at Villaraigosa.

Villaraigosa, who approved big raises for the city’s unionized workforce just before the Great Recession hit, took credit for layoffs, furloughs and pension cutbacks as the city struggled to remain solvent.

“As long as the teachers union hates him, I’ll support him for governor,” Riordan quipped, a nod to Villaraigosa’s friction with the powerful union.

As for the longtime pattern of L.A. mayors — including Riordan — losing campaigns for governor, Hahn suggested the hostility of Northern Californians remained a problem.

“I lived for a year up in San Francisco, and they really don’t like us up there,” he said to a burst of laughter. “And I didn’t quite understand it, because I said, ‘We don’t really even think about you guys.’ ”

Turning to the city’s ever-worsening traffic, Riordan said the construction of high-end housing in congested parts of town was drawing too many people into neighborhoods where it’s already tough to move at rush hour.

Villaraigosa, who led the campaign for a ballot measure that’s expanding the region’s bus and rail system, said concentration of new housing around transit stations was crucial.

“It wasn’t just about moving people; it was about re-imagining this town,” he said.

Hahn, 66, recalled the words of his father on a Red Car ride in the early 1960s, on the last day it ran between downtown L.A. and Long Beach.

“We have a perfectly good urban railroad here in Los Angeles, but we’re throwing it away,” Kenneth Hahn, then a county supervisor, told Jim and his sister Janice. “But mark my words, one day we’ll have to build it back.”

michael.finnegan @latimes.com