Passengers eat, drink, and frequently move in and out of the car during a road trip. A paper map or set of printed directions easily gets shoved into a seat during a stop, or worse yet, ruined if food or drink is spilled on it. Upon arrival, directions and maps are even more likely to get misplaced or damaged. To keep maps and directions safe during the trip, laminate them.
For around $30, a home laminating machine will seal standard letter size pages. Copy and print stores have the capability to laminate larger maps for a minimal fee. Alternatively, you can use contact paper to cover paper maps.
Pro tip: you can draw your route on a laminated map and easily wipe the mark off, if you change your mind.