Question Low beam headlights are effective for vehicles driving at speeds of up to: Answers 10 mph. 25 mph. 50 mph. 70 mph. Explanation Low beam headlamps are only effective when driving at speeds of up to 20 to 25 mph. Avoid driving too fast for what you can see within your headlamps. Pass your DMV Written Test with flying colors Take me to the cheat sheet Florida This questions appears in the following tests: Florida Practice Test 4 Florida Practice Test 23