The Kingsroad seems pretty good (good enough for Robert and Cersei to have wheelhouses on their way to Winterfell). Could Tywin have wheeled his troops down to the Trident instead of a force march after the Battle of the Green Fork, losing less men to exhaustion and getting more out of his mounted knights? What about amphibious boat-wagon hybrids? (Sorry for all this, it’s just the series seems to lack military engineering. There’s Tyrion’s boom chain and that’s about it…)