Does velocity, speed, or acceleration change at relativistic speeds?

[Ali Asadullah]

At high speeds, length contracts, time dilates and mass varies but what is the effect of high speed on speed itself and acceleration?

 

[bcrowell]

There are velocity and acceleration four-vectors, which transform according to the Lorentz transformation, just like any other four-vector: http://www.lightandmatter.com/html_books/genrel/ch04/ch04.html#Section4.2