At 0940 Station 11 was dispatched to Flying J for a commercial vehicle fire. At 0949 11-3 officer requested Station 7 to be added to the assignment. At 0951 hours Station 7 was dispatched to the scene with the report of a working fire. At 0953 Engine 7-2 went enroute with 5 personnel. Upon arrival crews found heavy fire in the cab and assisted 11-3's crew with deploying a second handline and gained access to the trailer. All crews did an excellent job and held the fire to the cab only. Crews cleared at 1035 hours. Units on scene: 11-3, 11-2, 7-2, 7-9, 11-8, 11-8A, County OEM for hazmat.