the safe speed of the road, regardless of limit.
http://www.ibiblio.org/rdu/sl-irrel.html
"Summary of Findings" is the best section to browse.
Very interesting, because lowering the speed limit raised accidents,
raising it lowered accidents, but people supposedly barely changed
their speeds.
"The data collected during this study indicate that there are no
benefits, either from a safety or operational point of view, from
establishing speed limits less than the 85th percentile speed."
