Complex sentence: The phrase "Don't Mess with Texas" is a trademark of the Texas Department of Transportation, and is part of a statewide advertising campaign, started in 1986, to reduce littering on Texas roadways.
Split into simpler sentences: The phrase "Don't Mess with Texas" is a trademark of the Texas Department of Transportation, which began as part of a statewide advertising campaign started in 1986. The intention behind the Don't Mess with Texas campaign was to reduce littering on Texas roadways.