This is a theme puzzle with the subject stated below. Find the listed words in the grid and when you have completed the puzzle, there will be letters left over. They spell out the alternative theme of the puzzle.
On the road
Alice Springs Axle Bogie Break Cab over engine Cabin Cap Coal Cows Curtainsider DAF Depot Diesel Dip Dirt Ford Fuel Gap Highway Hubs
Solution: 27 letters
International Loads Mood North Oil Pan Pie Plates Radar Refrigerated Rims SOS Spare Tarp Tax The Top End Tired Triple Turntable West