Mixed car/motorcycle/bicycle simulation
History and variations
Initially, MATSim would process "driver-vehicle-units", since in most western countries this was the most important mode. The design, however, always had multiple modes in mind.
The first, early, implementation of this was teleportation. For this, the router is notified that certain modes should be routed by teleportation, typically either with a travel time and distance estimation based on beeline distance, or on uncongested network travel times. The qsim just takes teleportation distances and travel times at face value, and generates departure and arrival events from that.
A more recent development here is that one can register arbitrary network mode routers, e.g. a "bicycle" router that would route only on the bicycle sub-network. For this, each link in the network.xml file needs to be correctly attributed; if there are links that can be used both by, say, "car" and "bike", they need to be attributed with both attributes. Again, the qsim takes the resulting distances and travel times at face value.
Christoph Dobler at some point added what is now available as "multimodal" extension (see http://matsim.org/extensions → multimodal). It essentially builds uncongested non-car links parallel to each car link. The main advantage over teleportation is that vehicles/persons have a position while they are on a leg, which is important for within-day replanning, most drastically for evacuation.
Another addition was to make the qsim directly multimodal-capable. Essentially, now, one can register, say, "car, bike" as main modes, and they will both be moved on the network. Maximum speeds of each vehicle are taken from a "mode vehicles file". By default, the link dynamics follows FIFO, i.e. the fast cars are stuck behind the slow bicycles. One can, however, use a so-called "passingQ" where this does not happen any more.