In　this　paper,　advanced　devices　such　as　the　dynamic　GPS　and　dynamic　electrocardiogram　equipment　have　been　employed　to　monitor　the　car　speed　and　the　driver＇s　heart　rate　in　carefully　designed　driving　tests.　Thirteen　selected　drivers　took　the　tests　by　driving　the　standard　cars　recurrently　through　the　same　highway　testing　section,　which　has　the　speed　limit　of　80　km/h　and　a　length　of　60km.　The　enormous　data　extracted　from　the　testing　results　have　been　summarized　and　analyzed　in　this　paper.　Based　on　the　correlation　analysis,　it　can　be　concluded　that　the　heart　rate　increment　of　the　driver　strongly　correlates　with　the　combination　index　of　the　curving　and　sloping　section.　On　the　other　hand,　no　apparent　correlation　can　be　identified　between　the　driving　speed　and　the　heart　rate　increment.　By　applying　the　linear　regression　analysis,　a　quantitative　model　has　been　established　for　the　longitudinal　gradient,　the　radius　of　the　horizontal　curve,　and　the　heart　rate　increment.　The　model　has　been　applied　to　retrieve　the　safety　threshold　values　for　the　geometric　design　of　the　curving　and　sloping　sections　at　a　specified　speed　limit.　The　research　result　of　the　paper　will　provide　the　useful　theoretical　reference　for　revising　the　Design　Specification　for　Highway　Alignment.　©　2010　ASCE.