Just in time for the holiday mass exodus from NYC, grassroots transit riders advocacy group Riders Alliance has released a report [PDF] that, they argue, demonstrates the need for a free shuttle bus to-and-from LaGuardia Airport—by far the lesser of the two NYC airports when it comes to public transit options.

The Port Authority Traffic Report for June 2015 [PDF] shows that only 12.5% of LGA customers travel to the airport by public transit.

According to the Alliance's findings, the MTA could implement a free shuttle bus in place of the MTA's current limited-service Q70, with little-to-no net cost and considerable benefit to many of the nearly 22 million LGA customers who passed in or out of LGA last year.

The Q70 currently runs directly to LGA from the Jackson Heights-Roosevelt Ave E/F/M/R stop or the Woodside LIRR stop, making no local stops. (The only other public transportation options to LGA at the moment are several local Queens busses, and the M60-SBS bus, which runs select from West 106th Street over to Astoria and on up to the airport.)

Eighty-five percent of the 350-odd Q70 passengers the Alliance surveyed over two months in 2014 already take advantage of the free transfer between the Q70 and the E/F/M/R at Jackson Heights. They also surveyed about 350 passengers at LGA's baggage claim, and found that 49% of those who don't currently take public transit to the airport would reconsider if there was a free subway shuttle.

Any lost revenue in fares, the Alliance argues, would be nullified by increased subway ridership from passengers converting to the subway.

"There are simple and cost-effective ways to help revive the spirit of LaGuardia while the airport awaits a proposed $4 billion overhaul by 2021," said Gene Russianoff of the Straphangers Campaign. "Heading the list is vigorously promoting and expanding the current non-stop shuttle bus to the subway."

Proposals to build a $1 billion AirTran to Willets Point and extend the N train to LGA above ground have both been, notoriously, disparaged and delayed. The Riders Alliance sees its solution as low-cost in comparison.

"In essence, nearly all riders are already riding the Q70 for free, but everyone pays in dwell time, a major criticism for Q70 ridership," said Riders Alliance board member Benjamin Kabak in an op-ed for Second Avenue Sagas. "Were the bus to be free, the Riders Alliance contends, even an increase in transit usage by just one percent of all LaGuardia Airport travelers would cancel out the free bus and in fact make the MTA money."

"Without a fare and with more frequent service and better advertising, the bus can be a key link to the airport rather than something those in the know take out of convenience," he added.

The study uses Boston as an example—that city piloted a free Silver Line bus to Logan Airport in 2012, and saw an 18% jump in public transit ridership in the first year. If the MTA saw such an increase, the report estimates, the transit authority would see an additional $587,000 annually in subway fares.

The Alliance also argues that signage for the Q70, arguably the most efficient route to LGA, does not specify its airport access. The new Free LaGuardia Subway Shuttle they've conceived would be bright blue and clearly marked, equipped with airport maps and airline directories on the interior.

The Q70 currently runs 24 hours a day, but infrequently during off peak hours. The free shuttle would run every ten minutes through the night, with countdown clocks.

Within a few hours of the Alliance's report being released—and concurrent with its rejection of a second free transfer for pay-by-ride straphangers—the MTA has already issued a strong statement in opposition to the plan.

"We wholeheartedly disagree with the premise that this could all be done at no cost to the MTA," said spokesman Kevin Ortiz. "First of all, one-fourth of riders do not come from the subway and don’t use the free transfer, and thus we would lose money on one out of every four customers under their plan."

"If ridership would continue to grow on the route to the level they claim, we would have to add service, and that costs money," he added. "And where would we find the buses?"

Kabak conceded that the subway's ability to handle the additional ridership that a free shuttle would hypothetically invite "is another question."