Which structure currently operates as a "virtual fence:"  Boarder Wall or Mexico-United States Barrier?
Mexico–United States barrier The Mexico–United States barrier is a series of walls and fences along the Mexico–United States border aimed at preventing illegal crossings from Mexico into the United States. The barrier is not one continuous structure, but a grouping of relatively short physical walls, secured in between with a "virtual fence" which includes a system of sensors and cameras monitored by the United States Border Patrol. As of January 2009, U.S. Customs and Border Protection reported that it had more than 580 mi of barriers in place. The total length of the continental border is 1,989 mi .
Presidio–Ojinaga International Rail Bridge The Presidio–Ojinaga International Rail Bridge (also known as the Presidio Rail Bridge or the Puente Ferro Carril Ojinaga) is an international bridge that crosses the Rio Grande (Río Bravo) between the cities of Presidio, Texas, and Ojinaga, Chihuahua, on the United States-Mexico border. The Presidio–Ojinaga International Rail Bridge is currently closed. It was damaged by fire on 29 February 2008, but there are plans to repair it. It is owned by the Mexican government and the state of Texas Department of Transportation. It was privately operated under a lease by Ferromex subsidiary Texas Pacifico Transportation.