In　order　to　find　the　relationship　between　posted　speed　limits　and　operating　speed　in　urban　expressways,　19　sites　were　randomly　selected　from　the　3rd,　the　4th　and　the　5th　Express　Ring-road　in　Beijing　and　the　spot　speed　and　headway　data　were　collected　at　first.　Then,　free-speed　data　were　reduced　from　the　original　data　according　to　certain　principles.　The　regression　analysis　of　posted　speed　limits　and　operating　speed　shows　that　there　exists　strong　linear　relationship　within　these　two　speed　terms.　The　percentage　of　operating　speed　exceeding　posted　speed　limits　increases　with　the　speed　limit　value.　The　relationship　between　speed　limits　and　operating　speed　established　here　was　expected　to　provide　some　quantifying　basis　for　transportation　agencies　to　determine　the　posted　speed　limits　at　speed　zones.