Paired (closely-spaced / compound) intersections and interchanges including staggered T intersections, freeway signalised diamond interchanges, freeway roundabout interchanges, diverging diamond interchanges (signalised), fully-signalised roundabouts (including signalised circulating roads), large signalised intersections with wide median storage areas, staged crossings at sign-controlled intersections, pedestrian crossings near intersections, and various alternative intersection and interchange arrangements can be modelled as a small network using SIDRA INTERSECTION. Common element for these facilities is the limited queue storage space available in internal approaches, therefore strong possibility of blockage of external approach lanes. It is also necessary to pay careful attention to lane utilisation in the analysis of such paired intersection cases in particular, and in network analysis in general.
Most signalised paired intersections need to be modelled as a Common Control Group (CCG) operating under a single signal controller using the method available in SIDRA INTERSECTION.
Use the Define CCGs and CCG Phasing & Timing dialogs in the NETWORK INPUT section in the Project pane under the Network tab. The Define CCGs dialog allows definition of Common Control Groups for sets of directly connected signalised Sites controlled by a single signal controller. When Common Control Groups are introduced in this dialog, the CCG Phasing & Timing input dialog will be available. This dialog includes a Select CCG tab and a set of CCG Phasing & Timing tabs similar to the Phasing & Timing input dialog for individual Sites.