Vertical　curves　shall　be　simple　in　application　and　shall　result　in　a　design　that　is　safe,　comfortable　in　operation,　pleasing　in　appearance,　and　adequate　for　drainage.　This　study　is　to　identify　changes　of　drivers＇　work　load　by　quantitative　measurement　of　psycho-physiological　load　by　using　advanced　physiological　signal　measurement　apparatus　when　they　drive　on　two-lane　highway　in　the　mountain　area,　and　then　analyze　changes　of　drivers＇　psycho-physiological　load　by　using　the　Power　Spectrum　value　of　heart　rate.　This　study　constructs　the　model　based　on　comfort　driving　by　analyzing　the　relationship　between　the　increase　rate　of　heart　rate　and　the　lengths　of　grade　and　the　average　speed　respectively　using　experimental　data　measured　with　RTK　GPS　receivers.　Speed　experiments　are　conducted　by　truck　on　two-lane　highway　in　the　mountain　area.　Experimental　samples　with　different　speeds　reflect　different　driving　conditions　in　the　test　track.　And　this　study　gives　the　reasonable　value　of　vertical　curve　design　parameter　to　realize　the　human　design　and　decrease　traffic　accidents,　which　reflects　the　psycho-physiological　characters　of　the　drivers　on　two-lane　highway　in　the　mountain　area.