The U.S./Mexican border at San Ysidro, California, is one busy place. In 2005 alone, more than 17 million cars and 50 million people passed through -- making it the world's busiest land border crossing. In an effort to speed things up, officials have unveiled a drive-through X-ray machine. From outward appearances, it looks like a simple car wash. In fact, the device is a huge "backscatter" X-ray imaging machine called a Z Portal. Car owners (or a border agent) drive through the device while the vehicle is screened for contraband. Downplaying any safety concerns, Custom and Border Patrol officials say a couple thousand trips through the Z Portal is equal the radiation exposure from a single traditional medical X-ray. The imaging machine was unveiled just last week, and San Diego officials claim it has already helped them seize more than 3,000 pounds of drugs. Thanks for the tip, Bob!

[Source: The Earth Times, photo by American Science and Engineering, Inc.]