The sentence that would benefit the most from a revision to a more informal voice is:
"Since 1970, the United States has experienced a distressing trend of workers increasingly driving in automobiles rather than using their city’s public transit system, which includes buses, trains, and subways."
This sentence uses more formal language ("experienced a distressing trend") and complex structure, making it suitable for a more casual rewrite. An informal version could be, "Since 1970, more and more people in the U.S. have been driving cars instead of taking public transit like buses and trains."