To　heighten　the　traffic　safety　level　of　urban　arterial　signalized　intersection,　signalized　intersection　upstream　functional　area　space　factor　length　formulas　for　the　perception-　reaction　area,　deceleration　running　area　and　queue　area　are　proposed.　On　the　basis　of　that,　through　analyzing　traffic　running　regular　pattern　in　signal　intervals,　which　include　red　time,　yellow　loss,　yellow　initiation　and　green　time,　upstream　functional　area　length　models　are　established.　Then　the　downstream　functional　area　length　model　considering　the　decision　sight　distance　is　proposed,　so　that　the　signalized　intersection　minimum　spacing　formula　based　on　the　functional　area　length　is　determined.　Finally,　applying　Technique　for　Order　Preference　by　Similarity　to　Ideal　Solution,　adjacent　signalized　intersections　of　one　arterial　are　taken　as　an　example　for　calculation　and　evaluation.　Evaluation　results　indicate　that,　compared　with　the　present　condition,　the　adjacent　signalized　intersection　area　which　satisfies　the　minimum　spacing　has　the　higher　traffic　safety　level.　When　the　spacing　is　larger　than　the　minimum　value,　the　traffic　safety　level　of　the　area　tends　to　be　stable.　It　can　be　seen　that,　through　modeling　the　functional　area　length　based　on　signal　timing,　the　proposed　minimum　spacing　calculation　method　could　optimize　signalized　intersection　spacing　schemes　and　heighten　the　intersection　location　rationality.