So many motorists are working from home and venturing out less amid the novel coronavirus outbreak that rush-hour traffic jams have begun to vanish in the Washington region and other major U.S. cities, according to recent traffic data.

On Tuesday morning, traffic on D.C.-area roads usually jammed inside the Capital Beltway moved an average 38 percent faster than on a typical Tuesday morning, according to Kirkland, Wash.-based INRIX, a traffic analytics firm that crunches data from vehicle navigation systems, cellphones and other devices. By that evening, speeds had soared to 51 percent faster than usual, INRIX said.

Increasing speeds mean decreasing congestion, said Trevor Reed, an INRIX transportation analyst.

“We’re seeing congestion not occurring anymore in a lot of U.S. cities,” Reed said. “In Seattle, we don’t have a morning rush-hour anymore. … It’s pretty surreal.”

Reed said traffic jams also have disappeared in San Francisco and Los Angeles, which, along with the D.C. region, typically top the lists of most congested U.S. cities.

On the Beltway near Interstate 270 in Montgomery County, vehicles usually bogged down bumper-to-bumper were spaced far apart and moving so quickly during the evening rush last week that motorists’ biggest problem would have been getting a speeding ticket.

Traffic is decreasing most during the evening rush because that’s when drivers typically run errands, ferry children and make other personal trips in addition to commuting, Reed said. However, many of those trips have become unnecessary as schools, restaurants, gyms and other businesses have closed.

The biggest effects began to hit March 11, when many companies started asking employees to work from home, traffic watchers said.

Taran Hutchinson, spokesman for the Metropolitan Area Transportation Operations Coordination (MATOC) program, said the amount of time that Washington-area highways had delays dropped by 20 percent the week of March 9 and by 40 percent on March 13, compared to the previous week.

“We’re seeing a lot of green” on real-time traffic maps, Hutchinson said. “You see blips here and there, but nothing like you’d see on a normal day.”

Since March 13, the cities recording the biggest improvements in average traffic speeds have been Los Angeles, Chicago, Boston and New York, INRIX said. By Wednesday morning, the firm said, Chicago’s traffic speeds were 77 percent higher than usual and Los Angeles vehicles were moving 53 percent faster.

In Northern Virginia, motorists are finding some trips are taking half the time. On Monday, driving the Beltway’s outer loop between the American Legion Bridge and Interstate 95 took 13 minutes, compared to the 24 minutes it took on average over the past month. An evening trip on southbound Interstate 395 that typically averaged 18 minutes over the past month took about 11 minutes Monday, according to the Virginia Department of Transportation.

John Townsend, spokesman for AAA Mid-Atlantic, said traffic congestion in regions with extensive rail and bus systems, like the Washington area, probably hasn’t dropped further because some commuters who can’t telework are driving to avoid public transportation.

On Wednesday, Metro reported that ridership had plummeted by 84 percent on Metrorail and by 63 percent on buses after the transit agency asked that both be used for “essential” trips only.

“There’s no discounting the fear factor in this,” Townsend said. “I think people perceive being alone in their car as the safest way to commute. It’s really social distancing.”

The drop in driving is also showing up in parking garages. In Montgomery County, the number of vehicles using public garages in Silver Spring and Bethesda last week was down 30 to 50 percent, a county spokeswoman said.

While traffic is moving much more freely, Hutchinson said, pockets of rush-hour congestion probably will continue to appear around hospitals and other facilities where workers must report. It’s also still occurring because of collisions, construction and other incidents, he said.

But free-moving traffic comes with its own problems, Hutchinson said.

“With no congestion anymore — or at least not like it used to be — speeds are up and crashes could be more severe,” he said.