BREEZEWOOD, Pa. — Millions of people who travel between the Mid-Atlantic and the Midwest each year fight through Breezewood, Pa., a strange gap in the Interstate System. A leg of Route I-70 brings drivers north from Washington and Baltimore to plug into the Pennsylvania Turnpike and the great road network that runs west to the heartland cities of Pittsburgh, Cleveland and Chicago.

But no ramps join these two huge highways at their crossing. Instead, drivers travel an extra two-mile loop that takes them out of rural Appalachia and into several suddenly urban blocks with traffic lights and a dense bazaar of gas stations, fast-food restaurants and motels.

“Things that make no sense: Breezewood, Pa. Why does the interstate turn into an interchange?” Stephanie Wonderlick recently posted on Twitter as she and her family returned home to Washington from Milwaukee.

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She is not alone. Many other drivers vent similar — often profane — anger and confusion about this notorious choke point. As a Washingtonian from northern Indiana who transits Breezewood for family visits, I have often wondered the same thing — a question that became more galling after my younger son, jolted by our sudden deceleration into the area’s stop-and-go traffic, threw up all over the back seat.

The answer lies at the intersection of politics and transportation policy. At a time when President Trump wants to spend a trillion dollars on infrastructure, the story of Breezewood offers a vivid case study in governance over such projects. It shows how legal quirks, powerful politicians and opaque bureaucratic procedures can influence decisions about how to spend taxpayer dollars.

One result is what critics call the preservation of an inefficiency that benefits a few while imposing widely dispersed costs on many.

I admit I have become a little obsessed with Breezewood, which sent me on a journey into its history.

It began as a truck stop when the builders of the turnpike placed an exit there during the Great Depression. Two decades later, when the I-70 leg was under construction, a since-changed law barred spending federal funds on a project that would send drivers directly, without a choice, from a free road to a toll road.

To get around that law, planners built the loop through Breezewood, giving drivers the theoretical option of avoiding the turnpike.

Map | Breezewood Interchange, Pennsylvannia Tpke.

Decades later, the social and environmental costs of this arrangement have swollen. I asked the American Transportation Research Institute, which studies congestion using data from GPS trackers on freight trucks, to scrutinize Breezewood. The institute estimates that about 1.5 million trucks make the connection through Breezewood each year. The same methodology suggests that about 3.5 million passenger vehicles do, too.

But 80 percent of truck drivers do not pull over to refuel, eat or rest, the GPS data shows. The institute estimated that if ramps were built permitting drivers to avoid Breezewood, the trucking industry would save as much as 142,362 hours in driver time and $9 million in operating costs every year. Add to that the time and money savings for car drivers, to say nothing of eliminating the unnecessary carbon dioxide emissions from the fuel that both types of vehicles burn to travel the extra distance.

But if there were such a connection, millions of potential customers wouldn’t be funneled into Breezewood. Jim Bittner, who manages the Gateway Travel Plaza that offers fast food and gas in Breezewood, and whose family has owned businesses there for three generations, said he knew that Breezewood annoyed the people who don’t stop but that preserving it was important for this economically struggling region.

His family’s businesses alone employ about 200 people, he said, and his family has taken out millions of dollars in loans to upgrade facilities they cannot move elsewhere. He called the prospect of a bypass a “sword of Damocles” hanging over Breezewood.

“Any second, someone could come in and say, ‘Time’s up, the faucet is turned off, no more business is going to be coming off that road,’” Mr. Bittner said in an interview. “And then what do I tell the bank? How do I pay the loan off? How do I keep employing people? Where do they find jobs?”

The most serious attempt to build a bypass came in the late 1980s, when a Democratic state senator from Pittsburgh, Michael Dawida, got into a rear-end collision at a Breezewood traffic light while returning home with his family from the Outer Banks in North Carolina. Mr. Dawida proposed a bypass, but the idea was blocked by the State Senate president at the time, who represented a district close to Breezewood, and by Bud Shuster, a Republican congressman at the time whose federal district included Breezewood.

Although Mr. Shuster was a leading member of the House Transportation Committee and was known for steering taxpayer funds to local highway projects, he made clear that he would never permit funding for a Breezewood bypass, Mr. Dawida recalled. (Mr. Shuster’s son, Bill Shuster, now represents that same district; his office did not respond to requests for comment.) Still, under pressure from the freight truck industry to do something about the problem, they reached a compromise of adding lanes in Breezewood to improve traffic flow.

“The ideal solution would have been to build a direct connection a quarter-mile down the road,” Mr. Dawida said. “They didn’t do that, but at least they did something.” Nevertheless, he said, when he goes to the beach each year, “I psychologically still can’t stop in Breezewood. I can’t.”

Since then, however, political power has shifted. Congressmen no longer earmark funds for specific projects, leaving states greater leeway to set priorities for highway projects spending. In 2015, when Pennsylvania began planning its current Transportation Improvement Program, it set up a website for public suggestions.

Proposals for a Breezewood bypass — salted with phrases like “ridiculous,” “extreme congestion” and “has been a nightmare for 50 yrs” — rolled in. Yet when the state finished the plan last August, it had no proposal for ramps connecting the turnpike and the Interstate. Instead, it called for resurfacing Breezewood’s roads.

A spokesman for the Pennsylvania Department of Transportation said that building a Breezewood bypass had “never been made a priority and put on the plan.” In interviews, lower-level state transportation officials explained why. The state’s system for deciding which projects to build starts with officials at the township and county levels coming up with lists of ideas, which are funneled upward in several stages of review.

At each stage, officials said, projects are reprioritized or removed, but rarely, if ever, added to the list. People mind their own areas rather than telling others what to do.

So, for a bypass to be considered, essentially Breezewood’s own Bedford County must propose it. Will it choose to damage its own economy?

The question answers itself.

“It’s just not an issue that really appears on the radar for us,” said Donald Schwartz, the Bedford County planning director. “It’s just not anything of a priority that’s been brought up through my office since I’ve been here, these five years.”

And that was that.

As I was finishing my research, I found Ms. Wonderlick’s Twitter post questioning why Breezewood exists, found her phone number and called her with the answer. She said she was glad to learn it. But as she contemplated many more years of slogging through Breezewood on family drives to Milwaukee, she sounded disappointed that no amount of infrastructure spending appears likely to fix it.

“It’s clear that it is designed, and still exists, as a tourist trap,” she said. “It’s clear they want to protect the interest of the town, and I very much understand that. But I do think it would be interesting for them to think about the needs of all the travelers and truckers who go through that area.”