[Mariner]

Dual layer with a road running down the middle, from the Pacific Ocean to the Gulf of Mexico.

Observation towers ever two miles and a quick-response battalion every 100 miles.

Subterranean sensors.

At least 100 exit gates, one way of course.

[dforest]

Alligators and crocs in the Rio Grande too.

[EinNYC]

Don’t forget the loose pit bulls running in the corridor, too. Can’t forget the pit bulls!