Vehicle Length Limits & Advisories - Sequoia & Kings Canyon National Parks (U.S. National Park Service) Because roads in these parks are narrow, winding, and steep, longer vehicles often cross the double yellow line and pose a danger to other drivers. Because of this, advisories are in place on some park roads. Drivers will be held responsible for any hazardous conditions caused by their actions. Follow the recommendations below for your safety and the safety of others.