"Slow down" or "speed up."
Pro tip: If you think you should speak up, don't.
Whether it's grandma puttering around in her Chrysler K Car or your irresponsible older brother Curt redlining his Z28, no one wants to hear your pace-related opinion. If you get into a vehicle with a guy that has a dream catcher tattoo on his neck and a skull shift knob, you should know full well that he's going triple the speed limit through a school zone. On the other side of the coin, anyone born before the Truman administration is going to come to a full stop during his or her left-handed turns. You either need to accept the passenger facts of life, or start riding your bike more.