The 14th Street car ban is speeding up the city’s slowest bus route — and more riders are now getting on board, transit officials crowed Tuesday.

Weekday ridership on the M14 since the ban’s Oct. 3 start date is up 17 percent compared to last September — from 26,350 daily trips to 31,031, according to MTA data.

Weekend ridership has seen even greater jumps.

Saturday ridership was 17,806 last September, but exceeded 25,000 on the two Saturdays since the car ban went into effect — a 40 percent increase. Sunday ridership increased by 34 percent, from 14,890 daily trips to nearly 20,000.

Transit officials attribute the spike to a dramatic uptick in bus speeds. It once took an average of 15.1 minutes to travel between Eighth and Third avenues, it now takes 10.6 — a 30 percent drop.

“This is what it’s all about folks. It’s about getting people back onto public transit,” MTA buses and subways chief Andy Byford told reporters Thursday.

“To do that, you have to make it attractive,” he said. “You have to show that it is the best way to travel along these key corridors.”

The car ban — which does not apply to large trucks or local deliveries and residents — is in effect between Third and Ninth avenues from 6 a.m. to 10 p.m.

The restriction was delayed for three months due to a lawsuit from West Village and Chelsea-based block associations, whose members were concerned about spillover traffic onto side streets.

Those concerns were overblown, city Transportation Commissioner Polly Trottenberg said — pointing to data from transportation analytics firm INRIX showing car speeds are basically unchanged on 12th, 13th, 15th and 16th Streets.

“We’re seeing pretty minimal impacts on the side streets, a little more impact on the avenues,” she said.

Amid years of declining bus ridership, the M14 stands out as one of the few routes in the city bucking the trend.

Speaking to reporters Thursday, Byford echoed Trottenberg’s comments from last week suggesting more car bans could be coming in the future — and that New Yorkers would “flock” to buses as a result.

“This is a forerunner for what I believe this city needs to do,” he said. “It’s all about taking tangible action to get the buses moving through congested streets.”