Moving　vehicles　in　the　urban　tunnel　will　discharge　pollutants　and　generate　the　traffic　force　airflow　at　the　same　time.　Reducing　the　concentration　of　pollutants　in　an　urban　tunnel　by　traffic　force　airflow　is　a　key　technology　to　decrease　the　operating　cost　of　tunnel　ventilation.　In　recent　years,　China　has　built　a　number　of　urban　tunnels　with　bifurcation　structures.　However,　previous　researches　on　traffic　force　are　most　concentrated　in　the　straight　tunnels.　In　this　study,　the　Changsha　Yingpan　Road　Tunnel　in　China　was　selected　as　the　main　focus　because　it　is　an　urban　tunnel　with　bifurcation　ramps.　The　traffic　characteristics　and　traffic　force　airflow　were　measured　by　the　project　team,　and　a　lot　of　data　were　obtained.　Combined　the　law　of　conservation　of　energy,　this　paper　mainly　studied　a　simplified　calculation　method　of　traffic　force　for　urban　tunnel　with　complex　bifurcation　structures.　Using　this　method　to　calculate　the　air　speed　induced　by　moving　traffic　in　the　Yingpan　Road　Tunnel,　and　compared　the　results　with　the　measured　data.　The　result　shows　that　the　calculated　values　have　better　compatibility　with　the　measured　data,　and　the　absolute　relative　error　is　less　than　8%.　The　conclusion　from　this　paper　can　provide　important　theoretical　basis　for　ventilation　design　and　safe　operation　of　urban　underground　tunnel　with　complex　structures.