It started five years ago, when Mercy Hospital built an express care facility on County Road in south Gorham. A couple of months ago, a Cumberland Farms opened next door. Now, an office building is being built down the street.

Businesses are starting to take advantage of the 25,000 vehicles that pass each day through the intersection of routes 22 and 114. And, with several residential properties recently rezoned for retail, more are sure to come.

But the last thing the area needs is more traffic congestion, planners say.

“It’s a horror show,” said Carol Morris, spokeswoman for the Portland Area Comprehensive Transportation System. “If it continues to develop the way it is … you’re not going to do anything but slow traffic down more.”

PACTS is funding a $100,000 study to help south Gorham and other growth areas in Greater Portland guide new development in a way that avoids contributing to the congestion.

PACTS will hold a meeting about the future of south Gorham and adjacent north Scarborough at 6 p.m. Thursday at the North Scarborough Grange Hall, at the corner of County Road and Saco Street. A week later, residents and business owners in Portland’s Libbytown will be invited to a similar gathering at the Clarion Hotel on Congress Street. Next month, PACTS will hold meetings in South Portland’s Thornton Heights and Westbrook’s Prides Corner.

Morris said PACTS will provide the communities with model ordinances for managing growth by concentrating development just off main corridors, creating village centers with a mix of uses, including housing.

Once the population density is high enough in places like south Gorham and north Scarborough, she said, public transportation becomes feasible, and that could relieve some of the congestion.

“None of this, of course, will happen soon, but you have to start somewhere,” said Morris.

Land-use management and public transportation were among the proposed solutions to suburban traffic problems identified in the Gorham East-West Corridor Study, a $1 million undertaking by the Maine Department of Transportation and Maine Turnpike Authority.

The study was conducted in response to a resolution signed by Gorham, Scarborough, Westbrook and South Portland in 2007 asking that the state look at the feasibility of building an east-west turnpike connection to relieve commuter traffic.

Although the study, which was completed in 2011, concluded that a turnpike spur or road-widening projects would be needed to achieve that goal, the state agencies have not moved forward with any projects.

The new PACTS effort aims to start implementing the study’s other recommendations, starting with land use.

Scarborough Town Planner Dan Bacon said he doesn’t expect much more growth along Route 22 in north Scarborough until the area gets hooked up to public water and sewer. But, considering its proximity to south Gorham, it makes sense to coordinate with the neighboring town on long-term plans, he said.

Gorham Town Planner Tom Poirier said the town would have started planning for commercial development in the area on its own if PACTS hadn’t provided help.

The chain of events happening in south Gorham is a common one in Maine, he said. Increasing traffic deters homeowners, who don’t want to deal with the cars and noise. At the same time, businesses see an economic opportunity.

“The amount of traffic that goes through is significant enough to start pushing that from a small neighborhood to more of a commercial component,” he said.

The way it’s developed, Morris said, will determine whether it becomes a place where people want to live or one that people only drive through.