Depending on the genre I think 400 pages is OK (my latest will come in at 390 but that's a commercial thriller).
But if you know it's sluggish in places, I think it may be a case of killing your darlings and being really strict with yourself about which sections to leave in and which to trim? I think a question to ask when editing is "does this move anything along (plot or character development)?" and if it doesn't, it may not earn its place. With the travel elements, is it possible to show (more than tell) by including more dialogue with local people, perhaps?