(Greg Gorden’s system, that he used for DC Heroes and Torg, is a logarithmic scale: ×X in the real-world measure is +Y in game number. (GURPS range modifiers and everything in EABA are similar.) Which should in theory mean that you can subtract a speed value from a distance value to get a time value. Except, in Torg at least, there’s a factor-of-10 error.)
Displacement, the distance and direction from the starting point (or an arbitrary origin, if you’re in to that sort of thing)
My high school physics teacher gave a quiz early on, which had a series of questions about race cars, to figure out speeds, positions, accelerations, and jerk (second derivative of velocity). the last question was to figure out the average velocity of the winner of the race, which was, of course, zero, since they were just driving around in circles. Many, many people got that wrong.