Does Caltrans design road surfaces to control how fast cars can travel on them?

No, we do not design roadway surface to control how fast cars can travel. What controls how fast cars can travel is the roadway’s design alignment such as the roadway’s radius of curvature and how much the cross slope of the curve is superelevated (banked).  Keep in mind that wet weather and sight distance also control how fast vehicles can travel.  We post speed limit signs (white signs) for speed enforcement and warning speed and/or condition signs (yellow signs) to alert motorists in advance.