MITSIM represents the network at the lane level. Each lane is described by two data items: (i) lane code, a unique identification code; and (ii) a lane change regulation and lane-use privilege code. Lane change regulations determine whether a lane change between adjacent lanes is allowed. Lane use privilege specifies the classes of vehicles that are or are not allowed to use the lane. For example, a lane may be assigned to high occupancy vehicles (HOV), electronic toll collection (ETC) vehicles, and/or commercial vehicles only. It may also exclude the use of the lane by particular types of vehicles such as over-height vehicles, trucks, etc. The lane-use privilege code for a particular lane can be any consistent combination of predefined basic types.
Each lane can be connected to one or more upstream and downstream lanes (e.g. at toll plaza, merging, and fork area) or has no lane connection at all (e.g. lane drop or network boundary). A lane connection table, which contains a pairwise list of lane codes, is used to represent the connections between upstream and downstream lanes.