Deciding how to go form point A to B is extremely important. It is part of the planing process of movement, most of the time we do not even realize this simple process but at times that significant effort and resources will be consumed on the task planning how to proceed should be the second step after deciding for a destination. Path selection is a decision making process by which one alternative is selected over another. Several procedures for making decisions have been outlined in effort to minimize inefficiencies or redundancies. These are idealized (or normative) processes, and describe how decisions might be made in an ideal world, and how they are described in official documents. Real-world processes are not as orderly.
Planning starts by selecting or deciding for a specific destination choice (this selection may in itself depend on many factors) fallowed by mode and route choices. The route selected my constrain or be depended on the modes of locomotion available.
It can be hard to decide if a path selection starts by establishing a destination, since all other components at some point have the same strength on the decision process. But undoubtedly if one is not required to go somewhere that there is no need to move, except if one is forced to move and then the destination may even be irrelevant. It all depends on the specificity of the situation that motivates the choice of a path.
In long trips, making a trip distribution (or intermediary destination choice or zonal interchange analysis). This step matches several origins and destinations to develop a “trip table” a matrix that displays the number of trips going from each origin to each destination. Priorities and resources available as well as costs (even effort) must be taken in account. This is basically turning any complex voyage in a sequence of smaller steps as to reach the final objective.
Trip distribution's zonal interchange analysis yields a set of origin destination tables which tells where the trips will be made, mode choice analysis allows the modeler to determine what mode of transport will be used. Mode choice analysis follows destination choice and may affect route choice.
Route assignment, route choice, or traffic assignment concerns the selection of routes (alternative called paths) between origins and destinations in transportation networks. To determine facility needs and costs and benefits, we need to know the number of travelers on each route and link of the network (a route is simply a chain of links between an origin and destination).
The Fundamentals of Transportation wikibook is a good work to examine in detail the complexity and analysis behind planning transportation.