"Anyspeed road-safety:" Momentum (blue) & kinetic energy (red) mirror driver (yellow) & pedestrian (green) reaction-times, respectively, as a function of "proper-velocity" (left) but not as a function of "coordinate-velocity" (right) in units of lightspeed c i.e. in map-distance per second on traveler or pedestrian clocks. This plot will work if lightspeed is 3×108m/s, 55mph (24.6m/s), or most anything else as well. "Momentum" is in of mc and "kinetic-energy" in of mc2 where m is the mass of the traveler's vehicle, while "reaction-times" (dashed) are in traveler or pedestrian per lightsecond of map-distance. From the panel on left, good news is that the rate of kinetic energy increase slows (red line) when proper velocity goes past a map lightyear per traveler year. The bad news is that relativistic speeds cause the passenger reaction-time (green line) to shrink more quickly.