Improper　design　of　the　geometric　elements　and　facilities　of　bikeway　systems　could　endanger　cyclists＇　safety　and　comfort,　resulting　in　an　increased　risk　of　bicycle　accidents;　such　accidents　sometimes　have　severe　consequences,　namely　casualties.　The　method　of　expression　for　cyclists＇　safety　and　comfort　and　the　question　of　how　the　correlation　of　these　factors　with　bikeway　characteristics-such　as　the　design　of　geometry　and　facilities-can　be　quantitatively　described　are　the　key　problems　facing　a　reduction　in　accident　risk.　Cycling　workload　can　be　employed　to　assess　cyclists＇　safety　and　comfort.　However,　there　has　been　little　quantitative　expression　research　on　this　topic,　with　no　clear　definition　of　cycling　workload.　The　quantitative　expression　of　cycling　workload　is　important　for　developing　guidance　for　the　safe　design　and　operational　management　of　bikeways;　this　is　necessary　for　controlling　conditions　that　might　induce　overworking　and　discomfort　among　users.　In　this　paper,　the　concept　of　cycling　workload　is　clearly　defined　based　on　cyclists＇　comfort　and　safety　formation　mechanisms.　Through　a　literature　review　and　a　comparative　analysis,　it　is　inferred　that　heart　rate　variability　(HRV)　can　be　used　as　a　quantitative　measure　and　the　low-frequency-high-frequency　ratio　(LF/HF)　can　be　used　as　a　physiological　signal　to　quantify　cycling　workload.　A　subjective　scale　was　found　to　effectively　express　cyclists＇　feelings　of　safety　and　comfort,　with　the　performance　assessed　according　to　a　human　factor　engineering　research　paradigm　that　classified　cycling　status　into　three　qualitative　levels-comfortable;　a　little　stressful;　and　stressful.　In　order　to　form　various　cycling　workload　states　and　to　obtain　the　relationship　between　LF/HF　data　and　various　bikeway　characteristics,　we　designed　a　field　cycling　experiment.　This　was　conducted　by　24　participants　who　wore　a　physiological　measuring　apparatus　under　three　different　bikeway　characteristic　scenario　types　including　variations　in　cycling　width,　direction,　and　bikeway　edges　at　four　cycling　speeds　in　the　10-25　km/h　range.　Statistical　analysis　was　used　to　address　the　collected　LF/HF　values　and　the　subjective　scale　results,　and　a　quantitative　model　for　assessing　cycling　workload　was　established.　By　adopting　a　classification　and　regression　tree　(CART)　algorithm　as　a　data-mining　method,　the　classification　threshold　values　(Delta　HRV)　of　three　cycling　workload　levels　were　obtained:　19　indicated　a　level　between　comfortable　and　a　little　stressful;　and　79　indicated　a　level　between　a　little　stressful　and　stressful.