Traffic Network Editing¶
An Aimsun traffic network consists of a set of road sections connected by a set of junction nodes. Road sections have attributes such as speed and lane count. They also have objects attached to them; bus stops, pedestrian crossings, detectors, meterings, and Variable Message Signs (VMS). Similarly nodes, which represent the road junctions have attributes which describe the connections they form between road sections (turns) and the associated stop lines and priority rules. A network also includes the connections to the demand centroids that determine where vehicles enter and leave the simulation and a set of subpaths which form partial routes through the network.
Road and Lane Types¶
Prior to creating road sections, the road section types and lane types must be listed in the model. These are the descriptions of the road types and the lane restrictions found in the model. i.e. Freeways, Trunk Roads, Urban Roads, etc. Lane restrictions can include lanes reserved for transit or lanes from which heavy goods vehicles are excluded. The Road Types and Lane Types form a library of road descriptions with the advantage that when changes are made to the type, they are automatically made in the road sections of that type.
Road Sections and Nodes¶
Road sections are the basic building blocks of a traffic network. The network is built by first editing the road sections, if this done manually, it is usually guided by a Background Image. Road sections are shaped to follow the line of the physical road and given attributes such as speed, lane width, capacity, and cost factors, initially taken from the road type, but can be subsequently edited for each section.
When the road sections have been created, they are linked by nodes which connect sections with turnings to form the traffic junctions with priority rules, stop lines, signals and turn speeds.
A transport network also requires a set of zone centroids (if OD demand is used) with connections to the road network to introduce vehicles into the network and remove them as they reach their destinations.
Creating and editing Centroids is documented in the Centroids section of the manual.
Subpaths are set of consecutive road sections which form a partial route through the network. They are used in gathering statistics and in routing vehicles on predetermined paths.
Creating and editing Subpaths is documented in the Subpaths section of the manual.