This　study　analyzed　the　relationships　between　alignment　elements　and　traffic　accidents,　traffic　flow　characteristics　and　traffic　accidents,　and　environmental　features　and　traffic　accidents,　which　were　based　on　the　presumption　that　drivers　on　the　freeway　had　better　conditions　for　steering　and　had　experience　driving.　The　findings　from　the　freeway　Jing　Jintang　in　plain　terrain　is　that　the　ideal　alignment　design　is　not　a　main　factor　causing　traffic　accidents.　There　are　strong　and　obvious　correlations　between　traffic　flow　characteristics　and　traffic　accidents　and　environmental　features　and　traffic　accidents.　By　means　of　nonlinear　regression,　the　crash　rates　prediction　models　were　constructed,　the　dependent　variables　are　crash　rates　including　three　types　which　are:　property　damage　only　accident　rate,　casualty　accident　rate　and　the　total　accident　rate.　The　independent　variables　are　the　characteristics　of　traffic　flow　and　the　environment.　The　three　models　can　be　used　as　management　tools　for　traffic　engineers　to　measure　the　safety　of　freeways.　©　2010　ASCE.