The Miracle Mile in Carlisle, Pennsylvania, is a vital capillary in the US freight transport system. Linking interstate highway 81 to the Pennsylvania Turnpike, the road is just an overnight drive away from half the country’s population. Thousands of trucks shuttle along it daily carrying everything from lumber to fizzy drinks.  Their drivers are well served. Three truck stops offer showers, burgers, video games and diesel fuel. Stores sell tail lights and hubcaps. The lonely can visit the Carlisle Truck Stop Ministry, its biblical tracts stacked in a white metal trailer, or a pornography emporium called Mature Fantasy in a red building behind a stockade fence.

These days the mile also acts as a recruitment ground for desperate employers seeking new talent. The magazine rack inside the Petro truck stop is piled with brochures listing scores of openings for people with commercial driver’s licenses. Roadside signs plead for applicants outside the offices of Knight Transportation, Keen Transport and ABF Freight. At the Flying J truck stop, driver Alvin Perry, taking a break before continuing his journey to North Carolina, says he has been poached four times in two years. “People change jobs all the time,” he says with a grin. “I just changed this week.”

If the US economy — growing at about 2 percent a year — is approaching maximum velocity, the trucking industry is a force governing its speed. Trucks move 70 percent of goods in the country by tonnage, but fleets are nearing full capacity. The constraint is not equipment; it is a lack of drivers.