The　author　clarified　the　relationship　between　volume　to　capacity　ratio　(V/C)　and　crash　rate　using　three　years　crash　and　traffic　flow　data　of　a　freeway.　This　relationship　can　be　used　as　a　basic　reference　to　predict　and　prevent　traffic　accidents.　The　hourly　crash　rate　model,　having　an　independent　variable　of　hourly　V/C,　was　established　by　regression　analysis,　and　the　relationship　between　crash　rate　and　V/C　ratio　represented　by　a　U-shaped　curve.　The　crash　rate　is　the　highest　in　the　low　hourly　V/C　range,　decreases　with　an　increasing　V/C　ratio,　and　then　increases　as　the　V/C　ratio　increases.　When　the　V/C　is　0.58,　the　crash　rate　is　the　lowest.