Which of the following increases the risk of a vehicle fire?

Under-inflated tires and loose fuel system connections are among the most common preventable causes of commercial vehicle fires. Under-inflated tires generate excess heat from flexing as they roll, and the heat can ignite the tire's rubber or nearby flammable surfaces. Loose fuel connections leak diesel or gasoline that can be ignited by hot exhaust components or a spark. Other risk factors include short circuits caused by frayed wiring, leaking hydraulic lines near hot surfaces, and accumulated grease and dirt around the engine. Pre-trip inspections should check tires for proper inflation and damage, verify all fuel and hydraulic connections are tight and free of leaks, and confirm that wiring is intact. Most commercial vehicles carry a B:C-rated fire extinguisher and reflective triangles by regulation.