Contrary to common perception, it’s not out-of-state tourists on their way to Mount Desert Island who are clogging the midcoast’s U.S. Route 1 corridor during the summer.

Interviews with more than 800 drivers and passengers last July and August – part of a Department of Transportation initiative to create a kind of comprehensive plan for the corridor – showed that most travelers on Route 1 are Mainers moving from one activity to another in the area.

At all but one of the survey stations, out-of-staters accounted for only 15 percent to 29 percent of Route 1 drivers. The exception was the Camden survey location, where 43 percent were out-of-state residents.

So-called through-trippers – who began traveling outside the corridor and whose destinations were also outside the corridor – typically accounted for one-fifth or fewer of the trips.

The exceptions were at or near the ends of the corridor: in Brunswick, 45 percent were through-trippers; and in Belfast and Searsport, 31 percent and 44 percent respectively started and planned to end their travel outside the area.

The research is part of the Gateway 1 initiative, and it is being analyzed by DOT staff and a steering committee made up of representatives of municipalities from Brunswick to Prospect.

Except at the eastern-most survey station – Searsport – half or more of Route 1 drivers live in the midcoast area at least part of the year. Most are year-round residents, but a significant minority appear to be seasonal residents.

The surveys also showed that most Route 1 drivers are middle-aged. The median age was typically mid- to late-40s. The oldest median was at the Camden station (52.5 years) and the youngest was at the Waldoboro station (40.9 years).

While those 65 and older make-up 18 percent of Maine’s driving population, they represented between 7 percent and 14 percent of the drivers at the survey stations.

Work was the second most frequent destination at five of the survey stations, accounting for half to two-thirds at most of the stations. Shopping was the most frequent trip end in Camden and the second most frequent at the Rockland, Bath and Searsport stations.

And even in the summer, a majority of vehicles on Route 1 have no passengers.

Former State Planning Office Director Evan Richert, who is working on the Gateway 1 effort, said the conclusion that can be drawn is that local traffic is the main culprit of congestion.

“This means that out-of-state travelers and Mainers from outside the midcoast who are using the corridor add to the problem, but they are not the fundamental cause of the problem,” he said.

Richert also noted that traffic problems in the corridor appear to be linked to the dependence of area residents, both year-round and seasonal, on Route 1 as a major travel route in their everyday lives.

He also said the developing pattern of land use – which dictates how and by what route area residents will travel to work, shop and meet other needs – is also a major contributor to congestion.