What a travel coat needs to do
The primary requirement of a travel coat is recovery — the ability to shake out the creases of a long journey and present itself cleanly without pressing. This is largely a function of cloth: a tightly woven, fine wool-cotton blend or a travel-weight fresco recovers from folding much more readily than a loosely woven flannel or a cotton.
Weight is the second consideration. A coat that weighs three kilograms becomes a burden on a long journey and uses up valuable luggage allowance. A fine travel coat in a 300–350 gsm cloth is light enough to wear for hours without fatigue and packs to a fraction of the bulk of a heavier overcoat.
Construction for a travel coat focuses on these requirements: a lighter canvas than a heavy overcoat, seam construction that presses out cleanly, and details — collar, pockets, buttons — that are proportioned to remain correct through travel use.