Q. If one is traveling and space and weight are of the essence, does one have to take with, both his Shabbos and weekday taalis, or can he wear his Shabbos taalis for all prayers?
If one is medakdek (careful) to use special Shabbos shoes, can he be lenient when traveling?

A. From Shulchan Aruch (O.H. 262: 3), Mishna Berura and other Poskim it appears that there are two distinct opinions as to how to comply with the obligation to wear special and dedicated clothing in honor of Shabbos. Halachikally, it suffices if the suit and hat are used only for Shabbos, while inner garments including shirts, as long as they were washed for Shabbos, that already makes them special and dedicated. Shoes are similar, and they should be shined or cleaned. (Rav Poalim 4: 13, Yisodei Yeshurun p. 26, et. al.).
However, others assert that all clothing should be dedicated only for Shabbos use, including shoes and taalit kattan (Arizal and Mekubalim as quoted in Magen Avraham ibid. 2, Moreh Be’etzba 4: 139, Kitzur Sheloh, et. al.).
In time of need as when traveling, Horav Shlomo Miller’s Shlit’a opinion is that in need he can take only one taalis. If the weekday is just as good, he may want to use that one.
the Rov also maintains that one can be lenient with shoes when traveling.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a