There are already too many, they're too big and add to deterioration of the nation's highways and bridges.
railroads

Teamsters President Hoffa Says “NO” to Larger Trucks on America’s Highways
(via gas2.org)
Submitted by MaxMaxL on Fri, 2008-07-11 19:47. | Tags: transportation | Biodiesel | clean air | congress | environment | fuel | Hoffa | railroad industry | railroads | semi-trailer | semi-trailer trucks | Teamsters President Hoffa | Teamsters Union | trucking | trucking industry | trucks