On a rough day, a bus ride in New York starts like this:

Then there are the traffic jams …

the mistimed stop lights …

the bunched-up buses …

and the cars blocking the bus lane.

Zohran Mamdani has made this grim experience central to his pledge to improve city life. Can his bus plan actually do that?

Some of the slowest buses in America plod through New York, stopping and starting, bunching and idling, at about eight miles per hour on average. Speeds have improved little over the past decade. The least reliable buses seldom show up on time.

Zohran Mamdani has built a strikingly successful mayoral campaign by tapping frustration with this system and marrying it to his broader campaign pledge to make New York more affordable.

“Fast and free buses,” he has promised, the two goals always locked together.

Get rid of fares, in theory, and that should speed things up, ending the backlog of riders lined up at every stop. More bus lanes and better infrastructure could bolster those gains. And making buses free would be a boon, Mr. Mamdani argues, for New Yorkers who have said in surveys that they’ve often struggled to come up with fare money.

“Today in the wealthiest city in the wealthiest country in the history of the world, one in five New Yorkers cannot afford the bus fare,” Mr. Mamdani said, defending his plan in the campaign’s final debate last week. Give people back that money, and more of their time, he suggests, and the economic benefits for the city would outweigh even the cost of a fare-free program he estimates could run $700 million a year.

Critics, and even some transit advocates, warn that his two goals are in tension: Spend such vast sums subsidizing the bus, and there won’t be much left over to improve it, especially at a time when the federal government is undercutting support for transit and the economy is shaky. Under any reasonable estimate, the annual cost to the city of making buses free would be more than transit officials expect to raise this year from congestion pricing, the Manhattan tolling program in the middle of its own political fight.

Whether fast buses and free ones can really go together depends on many questions, some beyond a mayor’s control, including whether Gov. Kathy Hochul would cooperate on higher taxes to raise revenue. Even if Mr. Mamdani were able to eliminate fares, what effect would it really have? And would it be enough to change the slog of riding a bus in the city?

Free and maybe faster

To understand the ambition of Mr. Mamdani’s plan, it’s helpful to first take in the vastness of New York’s bus network. It’s at a whole other scale from the subway system (and from any city currently running free buses):

Mr. Mamdani, who is the front-runner in the Nov. 4 general election, first championed the idea of free buses by pushing for a one-year pilot that made a single route in each borough free for one year starting in September 2023. Expanding the idea citywide would cover 340 routes that carry about 1.5 million paid trips per weekday.

Those rides represent a lot of money that the Metropolitan Transportation Authority, which runs the bus and subway systems, would no longer be collecting at the fare box. The fare today is $2.90, set to rise to $3 in January (although the actual fare collected per paying rider is more like $1.90, after accounting for free transfers and discounted fare cards). If the city were to pay for this instead, the total cost would depend on ridership numbers.

The M.T.A. says the cost of a free-fare program is probably higher than Mr. Mamdani’s estimate. As the authority cracks down on fare evasion, and ridership and fares increase, it projects that by 2028 the annual bus fare revenue, including paratransit, could exceed $1 billion — much higher than the campaign’s numbers.

About a quarter of bus riders also transfer to the subway. And if they haven’t paid for the first leg of the trip, the M.T.A. fears that more passengers may be inclined to skip the train fare, too.

John J. McCarthy, chief of policy and external relations at the M.T.A., said in a statement that the authority was pleased with the attention that transit has gotten in the mayoral race, but also expressed caution about making the buses free without more study.

“Why is congestion pricing successful? Because we took the time to study its benefits and impacts,” he said about the yearslong review for the toll program. “This proposal would demand the same kind of rigorous analysis.”

Still, the Mamdani campaign says the overall cost is relatively small — less than 1 percent of the city’s annual budget. But for the M.T.A., fare revenue covers about 19 percent of its $4.8 billion bus operating budget.

Mr. Mamdani suggests that the economic benefits of free fares could be twice as large as the costs. That’s hard to evaluate (the figure includes assigning a dollar value to the time you’d save by spending less of it stuck on the bus). His other claim is that eliminating the fare would itself speed up the buses.

That is theoretically true. All those seconds it can take each passenger to root around in a pocket, count out change or fuss with the card reader — at every stop — add up to real delays. And just one rider doing this can be the difference between making and missing a green light.

But New York’s own pilot program illustrates one hitch. Across all five free routes, ridership increased during the pilot by about 30 to 40 percent, mostly driven by existing riders taking more trips. The buses, however, actually slowed, because all those new riders still had to board the bus and request stops, offsetting the time savings from getting rid of fares.

That’s another complication: If ridership rises substantially, you have to add service to keep up with it, or you may not see any speed benefits. And that costs money, too.

Mr. Mamdani cites an estimate that free buses could shave 12 percent off trip times. The number comes from Charles Komanoff, a longtime transit advocate and mathematician whose traffic modeling helped inform congestion pricing. He first tried to assess the impact of free buses in 2007, as part of a study of whether congestion pricing could generate enough revenue to make transit free.

“That idea of free transit — it was visionary, it was lovely, it was beguiling,” Mr. Komanoff recalled recently. Politically at the time, though, “it was completely impractical.”

He put down the idea for nearly two decades. Then last December, he heard Mr. Mamdani, polling at the time in single digits, talk about free buses at a mayoral transit forum.

In April, Mr. Komanoff published a new report that is the closest thing to a white paper for the Mamdani campaign on the topic. His 12 percent time savings relies on some of his 2007-era data (bus riders then dipped a card instead of tapping it). This fall, he reran his analysis again, after riding the B41 bus in Brooklyn with The New York Times to collect new data. He estimates that ending fares could cut 7 percent off a trip on the route, assuming the ridership stays constant. That would still be, he said, “a triumph” — an improvement akin to what drivers have seen inside Manhattan’s congestion zone.

Faster but not free