I only take what I need for emergency repairs and leave the rest at home. This consists of a few screwdrivers, a couple of adjustable wrenches, pliers, diagonal cutter, vise-grips, hacksaw, mechanic's hammer, two sizes of Crescent pliers, and a few kinds of tape, wire, hose clamps, bungee cords, hand operated drill and bits, multimeter.
My tools fit inside a small tool box that is 15" x 7" x 8" in size.
I only want to do minor repairs to last until I get home or to a garage. The adjustable wrenches take the place of many open end wrenches and are all that I need for repairs on the road. I don't take socket wrenches as the type of repair that would require them is not something I am going to do by the side of the road.
In my teens when I drove Willys it was a different matter and I took all kinds of tools and jack stands, pretty much everything but a welding torch.