Surely, it’s indisputable: Traffic in San Francisco, especially downtown, is miserable, worse than ever, barely bearable. That’s what everybody says.

Just how bad it’s become, however, is tough to quantify — statistics from a variety of sources don’t paint a clear-cut picture. What they show is an uneven — and confusing — mix of measurements, some confirming the widespread belief that gridlock is getting worse, others suggesting — counterintuitively — that congestion is actually easing.

Figures show that the number of drivers pouring into San Francisco from both the Bay Bridge and Golden Gate Bridge is up — but only slightly — while traffic volumes on many busy city streets have declined. Traffic speeds have increased at most key intersections, but the time it takes to drive a couple of blocks has also gotten longer.

Even in the age of plentiful data, statistics don’t always tell the full story, especially to drivers creeping through South of Market toward the Bay Bridge on weekday evenings, pounding their steering wheels as they sit through yet another red light.

“It’s undeniable traffic is getting worse,” said Joe Castiglione, deputy director for technology, data and analysis for the San Francisco County Transportation Authority. “It may vary from location to location, but there’s little debate traffic is higher.”

Ed Reiskin, director of transportation for the Municipal Transportation Agency, said complaints about congestion have been increasing. One of those complaints was directed at Mayor Ed Lee from Sen. Dianne Feinstein.

“We’ve been hearing from a lot of people,” Reiskin said.

‘A lot more’ cars now

The word on the street is the same.

“I feel like there’s a lot of cars,” said Winta Gebreslasse, who’s been making deliveries for SpoonRocket for the past year. “A lot of cars — a lot more than there used to be.”

Some of the most damning statistics come from Inrix, a traffic information company. At The Chronicle’s request, Inrix analyzed driving times from January through March on four frequently backed-up stretches of street, repeating an analysis Inrix did for the newspaper in early 2014. With just one exception, Inrix found times creeping up during the morning and evening commutes:

•On the Embarcadero at Harrison Street, the time to get through the intersection increased anywhere from six seconds to a minute and 12 seconds, depending on the direction and time of day compared to 2014.

•Drivers traveling on Market Street between Third and Seventh streets saw a rush-hour increase of four seconds to 34 seconds.

•On Montgomery Street, from Bush to Market streets, the time rose from 28 seconds to a minute and five seconds.

•And on Mission Street, between Fourth and Sixth streets, trip times increased between one and 11 seconds, except in the southwestern direction in the evening commute, when they improved by 32 seconds.

And, apparently, we’re not alone.

“What we had through the recession was a bit of a traffic holiday,” said Jim Bak, a spokesman for Inrix, referring to national studies. “What we’re seeing now is growth in traffic that’s three times the economic growth.”

San Francisco traffic in the middle of the day is also getting worse, Bak said, noting that travel times and traffic volumes downtown are nearly as high between 11 a.m. and 1 p.m. as during the morning commute.

While the Inrix data show that traffic is on the rise, other figures are not nearly as clear-cut.

Clogged intersections

To monitor and manage congestion in San Francisco, the County Transportation Authority studies traffic speeds at clogged intersections every odd-numbered year. Between 2011 and 2013, commute speeds at half of the intersections measured — all on Van Ness Avenue or Mission Street — increased, while half decreased.

Downtown, for instance, the average speed on Mission between Third and Ninth streets, heading southwest in the morning, dropped 3.4 miles per hour. On the stretch between the Embarcadero and Third, however, it picked up by 5.5 mph. In the evening, speeds on Mission, between Third and the Embarcadero, heading northeast, slowed by 3.9 mph, but sped up by 5.5 mph on the same stretch in the other direction.

Another authority study found that the number of vehicles passing through busy intersections in 2014 mostly dropped compared with averages from 2009-12. It found declines as high as 31 percent at Mission and Fourth streets, 20 percent at Broadway and Van Ness Avenue and 16 percent at McAllister and Leavenworth streets. Only Columbus Avenue at Broadway saw an increase in traffic volume.

Lower traffic counts

While it would seem that traffic volumes would grow as congestion worsens, at some point, the opposite becomes true. When congestion causes backups, fewer vehicles can squeeze through an intersection, resulting in lower traffic counts.

More people are driving into the city, figures show, though the increases are relatively small. The Bay Bridge, among the nation’s busiest toll spans, is carrying about 2.2 percent more vehicles into San Francisco than it did a year ago, according to the Bay Area Toll Authority. Traffic into the city on the Golden Gate Bridge is up less than 1 percent over last year, according to the bridge district.

All that seemingly conflicting information could leave drivers scratching their heads, but the reality seems clear to drivers.

Richard Rome, 32, a Coca-Cola merchandiser, said traffic congestion starts earlier and lasts later during both the morning and evening commutes. Anywhere South of Market from Sixth Street to the Embarcadero is bad, particularly in the evening.

“It’s really getting bad,” he said. “It’s been getting worse and worse for a couple of years now.”

Congestion seems worse

There are other factors — the changing transportation scene, the surge in construction and the frustration of harried drivers facing time pressures — that could help make congestion seem even worse than it is.

The transportation revolution that brought ride services like Uber and Lyft has added thousands of vehicles to the streets — estimates range as high as 15,000 — and many of those cars double park to pick up or drop off passengers. The city cannot regulate the ride services and the state Public Utilities Commission doesn’t restrict their numbers.

“They’ve put a lot more vehicles on the streets,” Reiskin said. “They’re all contributing to the increased traffic.”

Something else that’s increased: construction, as evidenced by the forest of cranes South of Market. Work on the Transbay Terminal and Central Subway, as well as city sewer and street repairs, and office and residential tower projects, obstructs lanes and frequently alters lane configurations, leading to traffic tangles that can change daily.

“Construction just makes the roads smaller and traffic becomes more congested,” Gebreslasse said.

According to the Municipal Transportation Agency, permits allowing contractors to block traffic temporarily have been climbing steadily since the first half of 2010. During that six-month period, the MTA issued 669 permits. This year, through April, 1,128 permits have been issued, on a pace to hit nearly 1,700 for the same six months.

Pain of driving

Construction is one of many frustrations that drive motorists to feel that the pain of driving in the city is increasing.

Leon James, a psychology professor at the University of Hawaii, has studied the psychology of traffic for the past two decades and is known as “Dr. Driving.” He says the stress of driving — which can be exacerbated by hassles like lane closures, construction, new bike or transit-only lanes and aggressive drivers — leads to the perception that traffic is worse even when numbers don’t back that up.

“It has to do with the experience of being in stuck traffic and getting home because it’s getting less manageable and the stress is increasing,” he said. “It’s more about the drivers than the number of cars.”

A recent study by Here, a traffic information service, found that driver perception of other drivers, changing road or weather conditions, and their position in a backup can affect whether they view traffic as congested. So can time pressure. When you’re in a hurry, traffic always seems worse.

James, in true Hawaiian fashion, said the solution is for drivers to mellow out, let go of the negative thoughts and give themselves more time.

“We have to change the concept of driving,” he said. “Right now it’s in a very low spot. It it has to do with aggression and competition. It leads to the emotional use of the gas pedal.”

San Francisco officials hope to ease the stress and negativity with a mix of technology and stepped-up enforcement. Ben Matranga, a senior aide to the mayor, said a congestion management plan to start Monday will use real-time data from the MTA’s new transportation control center to deploy parking control officers to direct traffic and crack down on scofflaws more effectively.

Cite traffic blockers

Parking control officers, working with police, will continue — and increase — their crackdown on drivers who “block the box,” stopping in the middle of intersections or crosswalks when traffic lights change, or double park. Officers will also cite drivers who stop in bus and tow-away zones or obstruct transit-only lanes. They’ll be especially on the lookout for delivery trucks that block traffic or bike lanes.

Tom Maguire, the MTA’s sustainable streets director, said the efforts will focus on intersections and streets that are congested, heavily used by transit, and dangerous for pedestrians and bicyclists. They include Pine and Bush streets in the Financial District, Fell and Oak streets through the Panhandle, Haight-Fillmore and Hayes Valley neighborhoods, and Folsom and Harrison streets South of Market, especially near the Bay Bridge. Other targeted streets will include Geary Boulevard, Geneva Avenue, Van Ness Avenue and 19th Avenue.

Law-breaking drivers are already getting more citations, he said. Officers have issued 82 percent more “don’t block the box” tickets through spring compared with last year, and the number of double parking citations is up 53 percent.

While the mayor is aware of Sen. Feinstein’s dissatisfaction, Matranga said, the congestion crackdown has been a year in the works and isn’t due to any single complaint.

“The mayor hears it from a lot of folks,” he said. “He wants us to get out there and take a proactive stance so that traffic flows, is predictable, is safe.”

Michael Cabanatuan is a San Francisco Chronicle staff writer. E-mail: mcabanatuan@sfchronicle.com Twitter: @ctuan