Mayor Pete had a fleet of 47 buses. Secretary of Transportation Pete Buttigieg will have a budget of $87 billion

Washington, DC(CNN) South Bend, Indiana has a transit budget of about $10 million, covering 47 buses and fewer than 100 full-time employees.

Now the transportation budget of its former mayor, 38-year-old Pete Buttigieg, appears set to take a massive leap -- he'll soon manage over $85 billion after President-elect Joe Biden appointed him this week to lead the US Department of Transportation.

Those who are familiar with Buttigieg's work in South Bend say he's well-suited for the job given his track record, intellect, and view of transportation as about more than moving vehicles. They point to his success in revitalizing South Bend's downtown. He redesigned streets, which attracted new businesses, boosted property values and made the city safer for pedestrians.

But now Buttigieg is stepping onto a national stage, with bigger and more complicated challenges than what he faced in a city of about 100,000. He will have to address the challenges facing the nation's transit and ridehail workers as well as integrate electric and autonomous vehicles.

C. Michael Walton, a transportation professor at the University of Texas at Austin, said that Buttigieg may not have as much direct experience as previous secretaries, but the most qualified candidates haven't always proven to be the most successful.

"With his youth and energy he has an opportunity to showcase the future of transportation," Walton said. "We need it, quite frankly."

The next mammoth shift in American transportation may be autonomous vehicles, and a debate is already simmering.

Advocates say they'll make roads dramatically safer, but Tesla's Autopilot, a partial autonomy system available today, has long been criticized by autonomous vehicle experts and the National Transportation Safety Board over safety concerns. Autopilot has been a factor in several high-profile deaths. Tesla releases data each quarter saying that Autopilot is safer than traditional driving, but the findings have not been independently verified.

The National Highway Traffic Safety Administration took a hands-off approach to Tesla's autonomous driving features during the Trump administration, but Buttigieg could be more aggressive -- especially as systems like Tesla's autonomous "Full Self Driving," now in the hands of a small group of members of the public without any federal testing, strives to supplant human drivers.

Buttigieg's presidential campaign called for leading the world in safe and zero-emission autonomous vehicle technology, and said he would call for a strong federal role for regulations and oversight.

Electric vehicle sales are growing, with Tesla having become the most valuable automaker in the world. Highway funding may soon be in flux, as roads have long been paid for with gas taxes. During his presidential campaign, Buttigieg campaigned for shifting to a tax based on miles driven, but how such a system can be successfully implemented remains to be seen. Oregon has experimented with such a program. Buttigieg may also be tasked with following through on Biden's call to invest in 500,000 electric vehicle charging stations.

Perhaps most pressing, Buttigieg may need to take action on public transit. Most transit agencies are considering severe cuts to their services, given low ridership during the pandemic, according to the American Public Transportation Association.

Even before the Covid-19 pandemic, public transportation agencies were struggling with declining ridership as Uber and Lyft burned billions subsidizing rides and attracted people away from public transportation.

The ridehail companies are already on Buttigieg's radar, as he protested with drivers outside Uber's headquarters in 2019 as they sought better wages and benefits It's possible he might push for better protections for gig workers. Biden spoke out against a California ballot initiative this fall that exempted Uber and Lyft from classifying their workers as drivers

Amid his successes in South Bend, Buttigieg didn't buck the broader national trend of declining public transportation ridership.

Ridership on South Bend's public transportation dropped 32% between when Buttigieg was elected mayor in 2011 and when he left office in 2019.

Other Indiana city saw steep declines, too. Evansville, Indiana saw a 42% drop during the same time, and Fort Wayne, Indiana saw a 16% decline. Both cities have public transportation budgets similar to South Bend's.

A topic more in his wheelhouse may be pedestrian safety. Deaths have risen nationwide in recent years.

The South Bend streets that Buttigieg redesigned had fewer severe pedestrian crashes, according to Santiago Garces, who served as Buttigieg's chief innovation officer in South Bend. There were also fewer empty store fronts and higher property value, he said. One-way streets were converted to two-ways, bike lanes were added, and sidewalks were widened.

Biden has called for installing infrastructure for pedestrians and bicyclists, and Buttigieg's South Bend experiences may prove valuable.

"We were a city you drove through, and didn't stop," said Greg Downes, who was the CEO of a South Bend insurance company when he met Buttigieg during his first campaign for mayor. "There's nothing too big for this guy."

Downes said he already committed to another candidate for mayor, when he agreed to meet Buttigieg for a brief coffee before Buttigieg's 2011 campaign. Downes said after a two-and-half-hour conversation, he was so impressed that he agreed to support Buttigieg. He later served on Buttigieg's South Bend's Redevelopment Commission.

Kim Irwin, executive director of Health by Design, an Indianapolis organization focused on how public spaces impact public health, said she was encouraged by Buttigieg's selection given his past approach to transportation.

"He looks at things from a systems level, and sees how things are interconnected," Irwin told CNN Business.

Wide sidewalks allow for outdoor dining, which create vibrant street life. When streets aren't as wide to cross, and cars aren't moving at extremely high speeds, pedestrians also feel more welcome and drawn to city streets.

Now Buttigieg will see if he can translate his South Bend successes to a national stage.

Tom Wright, president of the Regional Plan Association, a New York transportation research group, believes Buttigieg is stepping in at the most important time for American transportation since the Interstate Highway system was developed in the 1950s.

"This is a pivotal moment," Wright said. "The policy and culture behind the American transportation system is up for grabs."