Endorsements are the cheapest pay raise in trucking. These are the ones that pay off fastest.
Hazmat and tanker
Hazmat requires a TSA background check and knowledge test; tanker requires a knowledge test only. Together they open bulk liquid and chemical freight, which is consistently among the best-paying regional work.
Doubles / triples
Doubles endorsements are essential for LTL city and linehaul work. Many union LTL carriers pay a premium per set pulled.