In every state the Department of Transportation / DOT, but what does the state DOT do?
The state DOT is the agency that oversees that particular state’s: state highways, mass transit, ferries and other transportation programs and regulations. The trucking industry is heavily regulated by the State and Federal Departments of Transportation.

Here are links to state DOT websites:

Alabama	Alaska	Arizona	Arkansas	California	Colorado	Connecticut
Deleware	Florida	Georgia	Hawaii	Idaho	Illinois	Indiana
Iowa	Kansas	Kentucky	Lousiana	Maine	Maryland	Massachusetts
Michigan	Minnesota	Mississippi	Missouri	Montana	Nebraska	Nevada
New Hampshire	New Jersey	New Mexico	New York	North Carolina	North Dakota	Ohio
Oklahoma	Oregeon	Pennsylvania	Rhode Island	South Carolina	South Dakota	Tennessee
Texas	Utah	Vermont	Virginia	Washington	West Virginia	Wisconsin
Wyoming