As excitement builds around Atlanta’s first modern streetcar, concern is building, too, among its biggest fans over what they call a potentially crippling flaw.

Namely, why would anyone wait 15 minutes for a streetcar to carry them a distance they could probably walk — for free?

Cities from here to Tucson, Ariz., are hankering for streetcars. But unless things change, among similar U.S. streetcar systems that are up and running, none has such a long wait at its most frequent time of the week for such a short distance1.3 miles end to end as Atlanta's streetcar will.

“That’s my biggest concern about the streetcar,” said David Emory, president of Citizens for Progressive Transit, a transit advocacy group. “It’s great that you have a flashy vehicle, but it’s all about frequency, given that it’s a short distance. To be effective it really has to be something you can just go out on the street and catch.”

Those concerned know it’s an issue, and Atlanta Mayor Kasim Reed said he is working on it. But he acknowledges that the stakes are high, and that running more frequent cars will take money.

“We’re working real hard to figure out how to fund the cut” in waits, said Reed, calling more frequent cars a key priority. Since the inaugural streetcar line could be the seed for the proposed Beltline transit system, “it’s really going to be essential that this run well and be a pleasant experience,” Reed said.

Streetcar planners could not say how much more frequent service would cost, but noted the city already owns more cars. So if they can find the money to operate three cars at once, rather than the planned two, at least they won’t have to buy a new vehicle. The operations contract should go out to bid soon, and, they stress, only then will they know what kind of frequency and fares the city can really get for its money.

The Atlanta streetcar hopes to draw a number of groups: downtown workers opting for a lunch trip; tourists going between attractions near Centennial Olympic Park and the Martin Luther King Jr. National Historic Site; and Georgia State University students, who live and study all along the route.

Planners also hope it will do more than just carry passengers from Point A to Point B. There is evidence that streetcars in other cities have proved to be an economic development engine that entices new retail business and residential development. For example, one enticement to ride in Atlanta would be that a pedestrian could go from GSU’s main campus to restaurants on the other side of the Downtown Connector without having to walk the forbidding and filthy space under the Connector bridge.

Lewis Foster, a GSU senior in graphic design, would love to take the streetcar. “That’d be awesome!” he said when told the route. “If it worked I’d probably take it every time I’m on campus.”

But when Foster heard it’s 1.3 miles from end to end with a planned 15 minutes between cars, his enthusiasm went south. “I can walk that,” he said. “That’s totally ridiculous. You should not wait 15 minutes.”

The streetcar’s budget is already pushing $93 million, versus the original $72 million plan. While the streetcar has ardent fans, it also has fervent opponents, from those who think rail is inefficient in a car-driving town to those who think this route won’t be useful to enough people. The rising budget has stoked their fire.

“Why would we do that?” said Foster’s friend, Kristiana Towns, also a GSU senior. “We already have horrible traffic. The streetcar will not help the situation at all.”

City officials counter that much of the budget hike is because after Atlanta won the $47.6 million federal subsidy for the streetcar, the city chose, with its eyes open, to fund upgrades intended to produce a more successful service. For example, it purchased new cars instead of used ones and is making streetscape improvements so the corridor will be attractive to passengers.

“As I say over and over, people have a decision to make about whether they want Atlanta to be a leading city, a modern city,” with a thriving tourism and convention business, Reed said. “And at the end of the day, the burden of this project rests solely on the city of Atlanta, and the leadership has voted for it.”

Reed and other advocates see the 1.3-mile streetcar line (2.7 miles round trip) as the seed of a future Atlanta streetcar system. With a successful start, they hope the line could soon sprout legs on either side, eventually reaching out to the corridor of the proposed Beltline transit loop around Midtown.

The city owns the streetcar and has funded it along with the Atlanta Downtown Improvement District, a self-taxing business group. But MARTA will manage its daily operations.

The city specified a 15-minute wait between streetcars in its application to win the federal grant that will pay perhaps half the line’s cost. The city needed to trim the project’s price tag to match the federal and local dollars available at the time, and to assure Washington it would be fully funded if it won the grant. Now Reed hopes money can be found from other sources to get the frequency to eight minutes.

Jarrett Walker, a Portland, Ore.-based planning consultant who has written about transit frequencies, expressed dismay at Atlanta’s proposed wait time: “Fifteen minutes to go on a line that’s a mile long?” He said people count wait time as a percentage of their total trip, and 15 minutes for 1.3 miles would be “quite inadequate.”

The city, MARTA, and the Atlanta Downtown Improvement District could provide no data that estimate how shorter waits would affect ridership compared to 15-minute waits. And to be sure, as a route in an urban core, the streetcar is surrounded by large numbers of potential riders. But as a general rule, longer waits mean fewer passengers.

Keith Parker, MARTA’s new general manager, wasn’t ready to say what the streetcar’s frequency should be, but he said there’s no question it impacts ridership. MARTA itself has seen that play out, especially with riders who have the means to choose.

“There’s a cost benefit to these things,” Parker said. “They particularly impact choice riders. Because if the person has the option of jumping into their car, then it could be a much tougher environment.”

David Maggio, an epidemiologist who works in downtown Atlanta, wouldn’t mind a streetcar that arrives every 15 minutes. He just wouldn’t take it much.

“It wouldn’t be something you’d do except for special occasions, because you’d be giving up half your lunch” if the scheduled cars didn’t line up just right, he said. If cars ran every five minutes, he said, it could be, “Oh, heck yeah, let’s add some variety” and take a streetcar trip.

Of 10 other U.S. streetcar lines similar to Atlanta’s, one has longer waits at rush hour: Little Rock, Ark., whose cars are never scheduled to run faster than 20 minutes apart. Jeffrey Brown, a Florida State University professor who studied a different group of streetcars, found that those in Little Rock and Tampa, Fla. — which also has a 20-minute wait — were the two least successful. And like most streetcars, those two have longer routes than Atlanta’s.

One similar streetcar, that in Dallas, runs every 15 minutes at its most frequent. But it boasts other attractions: It’s longer than Atlanta’s line, and riding is free.

The original plan was for Atlanta streetcar patrons to pay the regular $2.50 Breezecard fare, but the city is re-evaluating that.

All the other similar streetcars have tried to run more frequent service, at least at rush hour.

Seattle has a line about the length of Atlanta’s that was running every 15 minutes. That changed recently when businesses, including Amazon, banded together to fund 10-minute frequencies during afternoon rush hour for a year to see how it goes.

Ten minutes is a common range at rush hour. Others run as frequently as every five or six minutes, as in Boston and San Francisco.

In Memphis, it costs $1 to ride, less than city bus fare, and the shortest wait during rush hour for one of the 2.5-mile lines is 10 minutes.

“I think it matters for businesspeople,” said Alison Burton, director of marketing and customer service for the Memphis Area Transit Authority. “Sometimes we hear from them that they like the frequent service, because otherwise they may opt to go ahead and walk.”