Chances are, if you think of border shuttles at all, you think of them as road hazards or smuggling vehicles.
These vans ply the highways between border towns like Nogales or Douglas and bigger cities such as Tucson or Phoenix, and, yes, they've had their share of unseemly incidents over the years. Blowouts, raids, arrests.
The latest occurred Thursday morning, when two women traveling on a shuttle from Nogales to Tucson were busted at the Border Patrol checkpoint on I-19. They were carrying 6 pounds of methamphetamine in plastic bags hidden beneath piles of greasy fried chicken in two buckets.
Yet when you spend some time on the shuttles, or at their stations, you'll find they generally serve a straightforward purpose - inexpensive transportation for people traveling to and from the Mexican border.
Dig a little deeper, and you'll even find that, despite the sometimes disordered appearance of the stations or the vans, they're even decently regulated.
When I traveled to and from Nogales earlier this month, I went in a Garcia's Shuttle van that departed from a Sahuaro Shuttle station on South Sixth Avenue. (The short explanation of that mismatch is that the drivers and vans aren't generally employees or property of the line, such as Sahuaro Shuttle.)
Traveling in the first bench behind me were three members of the Valenzuela Valdéz family of Yavaros, Sonora, a port town in the south of the state. Their story - told in Spanish, the lingua franca of the shuttles - said a lot about the more common, licit uses of the shuttles.
José Valenzuela, 54, his wife, Francisca Valdéz, 50, and their 13-year old son, Juan, were in the penultimate leg of a 24-hour journey when I met them. The wear was starting to show.
They travel to and from Los Angeles every six months to get treatment for Juan, who has a cerebral paralysis that left him unable to speak or walk and causes convulsions.
Shriners Hospital in Los Angeles gives Juan treatment, including regular injections that control his convulsions, and arranges their one-time visas.
"Everything the boy needs, they give it to him. It doesn't cost us a cent," José Valenzuela said as the van churned south.
The help is indispensable for the doting middle-aged couple, who live off José's income as a fisherman - he spends his days and nights on a 22-foot boat in the Sea of Cortez.
For the family, the shuttles act as a bridge. They take an eight-hour bus ride to Nogales, Sonora, a short taxi ride from the bus station to the border, then jump on one of the many shuttles that line Terrace Avenue in Nogales, Ariz.
Although there are buses between Nogales and Los Angeles, they leave infrequently, whereas the shuttles depart several times an hour. Beyond the convenience, the shuttle lines always let Juan ride free, as they do for all the Shriners' patients who pass from Mexico through Southern Arizona. In Tucson, they catch the bus to L.A.
Their driver on the trip is José Sepúlveda, who lives in Tucson and works some of the time repairing railroad cars. Sepúlveda doesn't own the van he drives, but on the return trip, I'm with an owner-operator, Juan López Garcia.
When I asked how many miles López Garcia's 2000 Ford van has, he shook his head and said, "many miles." But he defended the quality and condition of the vehicles. He noted that the vans are inspected about every month by roadside Arizona Department of Public Safety officers.
Sgt. Jimmy Chavez of the DPS confirmed that shuttles must pull over whenever there's a roadside commercial-vehicle inspection. They also have to be inspected annually. However, the drivers don't need any special license or certificate, because that's only required for vehicles carrying 16 or more passengers.
Still, Chavez acknowledged, some shuttle lines are shadowy operators. A company that has been shut down by the Federal Motor Carrier Safety Administration for safety reasons sometimes reappears under a different name run by the same people.
Then there are the more newsworthy incidents, as in April 2010, when hundreds of federal agents swooped in on an alleged alien-smuggling operation that used certain shuttle companies in Southern Arizona.
But everyday experience on the shuttles is both more mundane and, in a way, significant. Most passengers I spoke with were visiting family, going shopping, or both.
On the Valenzuela Valdéz family's trip, they are heading home, and as the I-19 bends down into Nogales, José breaks into a verse of a traditional song about homesick Mexicans, "México Lindo y Querido."
For thousands of passengers, the shuttles are their link to Mexico.
Contact columnist Tim Steller at firstname.lastname@example.org or 807-8427. On Twitter @senyorreporter