The number of so-called “super-commuters” in LA County rose 22 percent between 2009 and 2017.

In Los Angeles County, where residents deal with demoralizing congestion and not-so-reliable public transit options, more than 150,000 people now spend 90 minutes or longer commuting to work in each direction.

That’s according to a new report from Apartment List, mined from census data, that focuses on a nationwide increase in so-called “super-commuters,” who spend upwards of 15 hours each week traveling to-and-from work.

Such employees have long been a staple of the East Coast workforce, where the downtown cores of cities like New York and Washington, D.C. draw in commuters from far-flung suburbs every weekday morning. Such long commutes are rarer on the West Coast, though the study suggests that may be changing.

As sprawling as Los Angeles may be, its share of super-commuters—now about 3.6 percent of the total workforce—is only slightly higher than that of the entire nation (2.9 percent). But commute times are growing quickly for many workers.

Between 2009 and 2017, the number of LA County residents with commutes longer than 90 minutes increased by nearly 30,000—a 22 percent spike. Those numbers include trips by car or on public transportation. Neighboring Orange County saw a 29 percent bump in super-commuters over the same time period, and in Riverside County, the number of super-commuters rose 31 percent.

Apartment List analyst Chris Salviati, who authored the report, tells Curbed that many of those facing long commutes in other counties are likely traveling to-and-from Los Angeles for work.

“Both Riverside and San Bernardino counties have super-commuting rates that are among the highest in the nation,” he says. “I think the vast majority are probably commuting [to LA] by vehicle.”

In Riverside, more than 7 percent of workers are now classified as super-commuters. San Bernardino isn’t far behind, with a super-commuter rate just over 6 percent.

Salviati explains that because many of these workers are likely traveling by car, these additional vehicles could worsen traffic congestion, which in turn makes shorter trips take longer.

“Infrastructure plays a big role here,” he says. “As a Metro area grows, if it doesn’t accommodate that growth with appropriate infrastructure, then traffic compounds and commute times are going to increase even for those living [near] the urban core.”

Higher levels of congestion also make it more difficult to get around efficiently using public transportation. In LA, buses that share lanes with private vehicles make up the bulk of the county’s transit system. When traffic is bad, buses are more likely to show up late, and riders transferring to other lines may miss their connections.

In a recent analysis of local bus speeds, UCLA lecturer Juan Matute found that vehicles in Metro’s system traveled 12.6 percent slower in 2017 than they did in 1994.

Salviati suggests that some super-commuters in LA County may not be traveling far distances; they could just be transit-riders faced with multiple transfers and the traffic-producing effects of urban sprawl.

If that’s the case, reducing commute times could be a matter of adding bringing more residents closer to the county’s major job centers.

“I think this really speaks to the need to rethink how we let our metro areas grow,” Salviati says. “When an area’s got a strong economy and is adding a lot of jobs, that’s a good thing. But then when you’re not adding enough housing in the right places to keep pace with that demand, that’s when we get into these issues.”