Capacity of shared-short lanes at unsignalized intersections

摘要

The calculation procedures in recent highway capacity manuals donot treat shared/short lanes at unsignalized intersections in anexact manner. The capacity of individual streams (left turn, throughand right turn) are calculated separately. If the streams share acommon traffic lane, the capacity of the shared lane is thencalculated according to the shared lane procedure from Harders ( i.e.the lengths of the short lanes are considered either as infinite oras zero. The exact lengths of the separate short lanes are not takeninto account. Therefore, the capacity computed from conventionalmethods is overestimated, whereas that from the shared lanes' formulais underestimated. This paper presents an analytical procedure, basedon probability theory, for estimating the capacity of shared andshort lanes. This procedure combines the existing procedures forestimating the capacity of shared and short lanes. Tested bysimulations in the style of the KNOSIMO simulation model, it can beused for arbitrary lane configurations. For simple shared/ short laneconfigurations, explicit equations are derived for estimating thecapacity. For complicated shared/short lane configurations, iterationprocedures are given. As a special case, the so-called flared minorapproaches are treated according to the theory derived.