Since Germany stopped trains here in mid-September as a way to slow the tide of refugees pouring northward, Taha has made 18 such trips.

“Normally in a month I would go to Munich one time,” he said last week at the taxi stand outside Salzburg Station. “People don’t know what to do without the trains. Some of them will spend anything.”

Meanwhile, grocery stores on the German side said their business has been halved as Austrian shoppers have been cut off. The local university lifted restrictions on handicapped parking to accommodate all the professors who commuted by train. For drivers, the frontier is a one-way valve: Getting to work isn’t so bad, but coming home can mean a two-hour delay at the road crossing, where Germany has implemented new passport checks.

Salzburgers say it’s as though a border that had largely melted away has suddenly risen up like one of the stone walls that once surrounded this medieval city. The free flow of people across national lines is a core ideal of the European Union’s grand effort at unification. But here, and in other parts of the European Union where cross-border trains have been halted, moving back and forth has taken on an Old Europe feel.