Direct service from the trolley to San Diego International Airport is finally on the cusp of reality. Give or take 400 feet and a highway crossing.

Come October, Green Line trolley passengers will be able to get off at the Middletown Station, walk 400 feet down West Palm Street and cross over Pacific Highway to a new airport shuttle stop.

The shuttle will travel a newly built $16.3 million roadway on airport property around the runway to the terminals, saving time and easing traffic on surface streets.

It’ll be the biggest improvement public transit passengers have seen in a while, though it’s still not what most hoped for, said San Diego City Councilman Todd Gloria. Indeed, grand plans for a multi-mode transit hub near the airport remain elusive.

“People envision a trolley spur up Harbor Drive,” said Gloria, who also serves on the board for SANDAG, the region’s planning agency. “I think what we are doing will work operationally, certainly in the interim … What we are doing, at least for now, is good.”

SANDAG will improve and expand the Palm Street sidewalk and crosswalk to make it compliant with federal laws for the disabled and more appealing to riders. The airport is building the on-site road and funding the shuttle service. Another shuttle will use the same route and service a new rental car center on Pacific Highway set to open in January. The shuttles will be free. Airport officials will also begin designing a $2.25 million park next to the future shuttle stop this month, though it’s unclear when that will open.

The desire for better public transit access to the airport has been at the forefront of San Diegans’ minds for a while now, especially as more and more cities do a better job connecting people to local airports via transit.

Yet San Diego’s trolley extension has been continually stymied by freight rail lines, the Coast Guard and limited ridership. SANDAG’s approved $1.7 billion Mid-Coast Corridor Transit Project will extend the trolley line north to University City, but offers nothing new near the airport.

The closest trolley stops remain two to three miles from the airport terminals.

For terminal access today, trolley riders, as well as those taking the Coaster commuter train, Amtrak and most city buses must first get to the downtown Santa Fe Train Depot and walk 500 feet to a nearby bus stop. An 11-minute bus ride on MTS Bus Route 992 brings you to Terminal 1, and a 14-minute ride brings you to Terminal 2.

Average weekday ridership on the route hovers around 1,400 people, MTS figures show, including about 490 airport pick-ups and 603 airport drop-offs.

Gloria said some of his constituents love the 992 bus.

“People are already being fairly multimodal if they are trying to get there by public transit,” he said. To those wary of the walk down West Palm Street, “You walk much farther from TSA to your gate,” Gloria said.

While the shuttle is a go, what’s less clear is the viability of a 90-acre transportation hub envisioned between the airport and Interstate 5. Buses, trolleys and trains, and even the state’s high-speed rail line (should it ever make it this far south) would all converge on the site.

The so-called Intermodal Transit Center remains on the long-term development plans for both the airport and SANDAG, but much is still unknown about the project, which SANDAG pegged at $170 million in 2014 without high-speed rail.

“Prior to getting on the (Airport Authority) board, I always assumed a very robust, well-integrated intermodal center either on the airport or immediately adjacent to the airport was planned,” said City Councilman David Alvarez.

But that vision “isn’t really on the horizon for the airport site,” he said. While there is interest, “I don’t think it’s a priority from the airport’s perspective. I don’t know if it’s a priority from SANDAG’s perspective.”

Federal spending restrictions may limit the airport’s ability to fund the center, Alvarez said, so “That’s where SANDAG would come in.”

Keith Wilschetz, the airport’s director of planning, also indicated the airport is taking cues from SANDAG for the project.

“Our charge is to operate San Diego International Airport. We focus on operating this airport, not surface transportation,” Wilschetz said. “The Airport Authority will likely assist in funding the pedestrian bridge over Pacific Highway that would link the ITC with the airport economy parking lot; however, a financing approach has not yet been prepared with SANDAG. When SANDAG is prepared to begin development of the ITC, we will work with them to prepare an appropriate funding approach.”

“The Intermodal Center is a question mark,” said Gloria. “Even with unanimous consensus around that concept, it’s still going to be difficult to achieve.”

Not only would acres of private and public property need to be secured, the project would require coordination and support from Caltrans, MTS, NCTD, the airport, SANDAG and others.

“I think the diversity of players coupled with the uncertainty of high-speed rail mean that our focus is on those other priorities that we have more consensus,” Gloria said. “SANDAG’s plate is pretty full and we have some very large complex complicated projects,” like the new Otay Mesa East Port of Entry at the Mexico border, the regional bike plan and the Blue Line extension to University City. “Those are projects that we have funding for.”

How the airport decides to develop its north side, across from the elusive transit hub, could also make a difference. Not too long ago, the airport considered building a passenger terminal on the north side, but that idea has been dropped.

Instead, airport board members will be asked in the fall to choose between five choices for how to rebuild Terminal 1 at its current location for $2.1 billion to $2.6 billion. A year and a half of environmental review will follow, officials estimate. A public meeting to discuss the still-unfunded proposals will be held July 14.