A pedestrian crosses over rush-hour traffic on the Southwest Freeway in Washington earlier this year. (Bill O’Leary/The Washington Post)

Brace yourself for the nastiest trafficalypse Washington has ever seen. It’s already happening. Many days, driving in D.C. feels like being stuck behind a presidential motorcade that’s plowing through cherry-blossom traffic. In the rain.

Traffic in Washington — always choked at rush hour — is unquestionably getting worse. The nightmare is being fueled, in part, by thousands of Uber users and Lyft lovers who are ditching public transportation and putting thousands of additional cars on the road in the process.

And who can blame them? Metro stinks these days. Uber and Lyft are often cheaper than public transportation, and the 135,000 daily riders who have left Metro are going to ride in something. Do the math. Be afraid.

Uber and Lyft, cities are finding, are not killing off taxis and keeping personal cars off the streets, as many had feared or maybe hoped when they started almost a decade ago.

"While many suggest that ride-hailing can be complementary to public transit, current evidence suggests that ride-hailing is pulling more people away from public transit in cities rather than adding riders," said the authors of a University of California at Davis study on the phenomenon.

The researchers asked folks in cities across America how they would travel if they couldn’t use the magic apps that make cars appear before them.

They found that “a majority (61%) of trips would have not been made at all.” Or, back-seat barons confessed, they would’ve made their trips “by walking, biking, or transit.”

Not by their own car.

Especially with the toll rates that premiered this week, with one-way travel from the Beltway to Washington on Interstate 66 reaching $34.50 during the morning rush hour.

See where I’m going with this?

Metro officials see it, too. Officials announced a study this week to try to crystal-ball our commuting future in light of the 135,000-a-day exodus.

This future is even scarier in light of a growing population of public-transit-phobes. Because the driverless cars that the on-demand crowd will love are coming faster than those flying cars Dr. Emmett Brown had promised Marty McFly. And that means the traffic forecast is an even bigger horror, with a chance of torment.

It’s no mystery why folks like on-demand transportation. It means you will be shielded from the rejection of taxi after taxi whizzing past you.

You don’t have to interact with people unlike you, avoiding the often colorful and sometimes fragrant experience that a city bus or the last Metro car is sure to provide.

It’s convenient, often cheaper, and it means you’ll probably be on time. That’s something you can’t often say on Metro anymore.

“Since Uber, I haven’t been on the Metro in 3 years. Not once,” wrote one Washington Post reader, identified as “join or die,” in the comments section of a story about this by my colleague Faiz Siddiqui.

Another commenter explained it in dollars and minutes, saying that “we took the metro into DC on Wednesday and it took 1hr 15 min to go from Silver Spring to Metro Center — Took a [Lyft] home the next morning — it cost $2 more than the metro fare for 2 people — and took 21 minutes. I’d say the drop is not due to Uber and Lyft existing — but Metro putting out such a bad product right now.”

I get it, but it took a while for me to get there.

I took a hard pass when Uber arrived in Washington, mostly out of solidarity with the city’s taxi drivers. A good taxi driver knows the city cold and almost always has a story to tell. It was one of the solidly reliable industries for Washington natives and a reliable entry for immigrants who are good at getting to know a city well.

And in my travels through D.C., I cringed at seeing the traffic patterns quickly changing thanks to ride-hailing services.

When you’re behind a cab, you know they may stop to pick up a fare or drop someone off. But then, suddenly, every other civilian Altima was doing the stop-and-start, lurching and swerving like Aunt Bea looking for an address. Early Uber drivers were no D.C. cabbies. And more and more of them are clogging the streets.

I confess I became a convert when Uber saved me when I was trying to transport 16 youth hockey players and their huge bags from a train station in South Bend, Ind., to a dorm at the University of Notre Dame, where the boys were attending a hockey camp.

I felt like Rudy Ruettiger, rejected by taxi after taxi when we called dispatchers, trying to get to Notre Dame. So I took the plunge and downloaded Uber. Within 10 minutes, we had a fleet of cars, big enough for the equipment, at our service. Perfect.

In Washington, ride-hailing services mean easier transportation for farther-flung city neighborhoods.

It’s also a perfect way to get a ride after Metro hours, and the UC-Davis study showed it helps keep plenty of drunk drivers from getting behind the wheel.

The catch, of course, is that these need-based cases­ aren’t the bulk of Uber and Lyft activity.

Most rides are taken by wealthier, younger folks who simply want to avoid the hassles of public transportation, the study found.

And when they leave public transportation, money leaves public transportation.

Chicago, battling gridlock, quickly figured this out. Mayor Rahm Emanuel (D) pushed a 15-cent surcharge on all Uber and Lyft rides that was approved and now goes straight into fixing public transportation.

But D.C. Mayor Muriel Bowser (D) isn’t proposing anything like that.

“There are a lot of things that are cutting into Metro ridership,” Bowser said in response to a reporter’s question at an event announcing a new hub for Uber drivers in the city. “I would put first among them the year-long SafeTrack [maintenance] program, and also the cutting back of hours at Metro. So I wouldn’t start with Uber — I would start with Metro itself.”

Yes, Metro needs help. And it’s up to leaders to find creative ways like the Chicago option to return Metro to the crown jewel it once was.

If that doesn’t happen soon, the city is going to be one big parking lot of people waiting, waiting for those flying cars to appear.

Twitter: @petulad