Welcome,
Merel!
The photos I've seen on the Burner Express so far have suggested that people are
mostly dressed just for travel, but may be wearing a festive hat or coat so they don't have to pack it.
No doubt the Burner Express is air-conditioned; that's another good reason to have a layer to wear.
And finally, you may be leaving the bus temporarily to shop or whathaveyou (if you are on a route with food stops) so it's best to wear something you are comfortable in, and that is street legal.
