Guild Wars 2

Do movement speed increases stack? Like the Traveler’s Rune with various signets?

No, only the highest value applies. Im using the signet of shadows for +25% movements speed and I see almost not difference when I get swiftness boon (33%).

I think that there is a limit of 33%. I have found that I do move faster then my 25% passive when I use my dodge that has a trait applied to it to move faster. I could be completely wrong but Im pretty sure it is this.