VIENNA — The desperate migrants and asylum seekers now flooding into Europe by the tens of thousands, and the inability so far to accommodate them in an organized way, may be starting to fray Europe’s commitment to erase old borders.

The evidence was on stark display Monday, as the Austrian authorities disrupted traffic from Hungary, causing backups of at least 12 miles, while inspecting vehicles for smuggled migrants. The crackdown could last indefinitely.

The official explanation was to avert another mass death of migrants like those found in an unventilated truck near Vienna last week, believed to be victims of a smuggling ring. But the practical consequences of the crackdown mean that routine passport-free travel between Hungary and Austria is no longer routine.