Class　1　highway　is　an　important　component　part　of　multilane　highway　in　our　national　highway　net　system　and　it　has　three　typical　cross-section　forms.　This　article　analyzes　the　effects　of　different　central　separator　type,　roadside　separator　type　and　roadside　development　degree　on　free　flow　speed.　Two　field　highway　survey　data　indicates　that　the　central　physical　separator　has　no　effect　on　the　free　flow　speed.　But　the　dual　amber　line　separator　can　lower　free　flow　speed　1.6km/h　when　traffic　volume　increases　100pcu/h.　seven　field　highway　survey　data　proves　that　roadside　development　degree　has　no　effect　on　roadside　physical　separator　highway.　If　physical　separator　is　changed　into　white　line　separator,　free　flow　speed　will　be　lowered　2.5km/h　when　the　roadside　development　degree　increases　10%.　Impact　of　access　density　on　traffic　flow　mainly　shows　on　highway　safety.　Traffic　accident　data　and　access　density　design　analysis　results　get　the　impact　of　design　on　traffic　flow.　It　introduces　the　concept　of　access　equivalent　intensity　and　establishes　the　relationship　between　access　equivalent　intensity　and　traffic　accident　rate.　Suggestions　are　proposed　to　amend　the　highway　design　standard.　©　2011　ASCE.