Question Which of these vehicles must always stop before crossing railroad tracks? Answers Tank trucks marked with hazardous materials placards. Motor homes or pickup trucks towing a boat trailer. Any vehicle with three or more axles and weighing more than 4,000 pounds. Explanation Trucks transporting hazardous loads must stop before they cross railroad tracks. Pass your DMV Written Test with flying colors Take me to the cheat sheet California This questions appears in the following tests: California Practice Test 25 California Practice Test 34