I think sandwiches using heartier bread (like french baguettes or ciabatta rolls) hold up better than softer sliced bread, if traveling. Sandwiches with cured meats also work well.
Italian Ciabatta Sandwiches
Ciabatta rolls, lightly toasted
Freshly sliced mozzarella
Basil and pine nut pesto
Marinated artichoke hearts, thinly sliced
Sliced tomatoes, seeds discarded
How long is the road trip - One day? One week?
For a day-long run, I could see hard salami & hard cheese surviving.
Also, Branston Pickle & sharp cheddar (maybe some really dry, aged stuff?) could make it. Of course, you have to like Branston Pickle!
Peanut butter & honey, blended prior to spreading, would also make it.
After a day, I think I'd resort to pre-packaged items or buy along the road.