Big rigs are 80,000 Lbs and 8 foot wide.

Most roadways are 12 foot wide.

Big Rig in The Center of the 12 ft lane Leaves 2 FOOT on each side of the lane.

An oncoming Big rig in the center of his lane has the same 2 ft space from the center line.

So when Two rigs meet, at 60 mph they only have a 4 foot space that keeps them from a head on collision @ 120 mph hit.

http://www.thetruckersreport.com/facts-about-trucks/