That has been devastating to small-business owners in places like San Ysidro, home of the busiest border crossing in the world.

Nor are any fences visible, like the barrier under construction near China's busiest border crossing at the city of Dandong.

Waiting as traffic inched forward through Macedonia's busiest border crossing with Serbia, a truck driver was asked what he was carrying.

Busia is the busiest border crossing between the two neighboring member countries of the East African Community.

Taba is the location of Egypt's busiest border crossing with neighbouring Israel.

Southeast of central Aranyaprathet, 6 km away, is the busiest border crossing between Cambodia and Thailand.

As drug agents have intensified air and sea patrols, traffickers have turned increasingly to smuggling on the ground, favoring in particular busy border crossing points.

This region plays an important role in the U.S. economy with its automotive industry and the country's busiest border crossing for commercial items.

On the busy border with Costa Rica, customs agents patrol on foot for lack of vehicles.

Or the traffickers drive her through a busy border crossing, and if she's blond and speaks English, she'll get waved right through.