Platapus, travel mode is a new feature that allows you to keep a hi-TC without being dropped out whenever you receive a new radio message/contact report. Great when you want to cross the Atlantic.
One of the great things about SH5 is the many improvements under the hood that are not immediately apparent, for example improvements to the mission editor and the campaign engine, some of them are discused here:
http://www.subsim.com/radioroom/showthread.php?t=163364