Editing Transportation planning (section)

===Technical process===
Most regional transport planners employ what is called the rational model of planning. The model views planning as a logical and technical process that uses the analysis of quantitative data to decide how to best invest resources in new and existing transport infrastructure.<ref name="Levy">Levy, J. M. (2011). Contemporary Urban Planning. Boston: Longman.</ref>

Since World War II, this attitude in planning has resulted in the widespread use of travel modelling as a key component of regional transport planning. The models' rise in popularity can also be attributed to a rapid increase in the number of automobiles on the road, widespread [[suburbanization]] and a large increase in federal or national government spending upon transport in urban areas. All of these phenomena dominated the planning culture in the late 1940s, 1950s and 1960s. Regional transport planning was needed because increasingly cities were not just cities anymore, but parts of a complex regional system.<ref name="Johnston">Johnston, R. A. (2004). The Urban Transportation Planning Process. In S. Hansen, & G. Guliano (Eds.), The Geography of Urban Transportation (pp. 115-138). The Guilford Press.</ref>

The US process, according to Johnston (2004) and the FHWA and [[Federal Transit Administration]] (FTA) (2007), generally follows a pattern which can be divided into three different stages. Over the course of each of three phases, the [[metropolitan planning organization]] (MPO) is also supposed to consider air quality and environmental issues, look at planning questions in a fiscally constrained way and involve the public. In the first stage, called preanalysis, the MPO considers what problems and issues the region faces and what goals and objectives it can set to help address those issues. During this phase the MPO also collects data on wide variety of regional characteristics, develops a set of different alternatives that will be explored as part of the planning process and creates a list of measurable outcomes that will be used to see whether goals and objectives have been achieved. Johnston notes that many MPOs perform weakly in this area, and though many of these activities seem like the "soft" aspects of planning that are not really necessary, they are absolutely essential to ensuring that the models used in second phase are accurate and complete .<ref name="Johnston"/>

The second phase is technical analysis. The process involves much technical maneuvering, but basically the development of the models can be broken down as follows. Before beginning, the MPO collects enormous amounts of data. This data can be thought of as falling into two categories: data about the transport system and data about adjacent land use. The best MPOs are constantly collecting this data.<ref name="Johnston"/>

The actual analysis tool used in the US is called the Urban Transportation Modeling System (UTMS), though it is often referred to as the [[Transportation forecasting#Four-step models|four-step process]]. As its nickname suggestions, UTMS has four steps: trip generation, [[trip distribution]], [[mode choice]] and trip/route assignment. In trip generation, the region is subdivided into a large number of smaller units of analysis called traffic analysis zones (TAZs). Based on the number and characteristics of the households in each zone, a certain number of trips is generated. In the second step, trip distribution, trips are separated out into categories based on their origin and purpose: generally, these categories are home-based work, home-based other and non-home based. In each of three categories, trips are matched to origin and destination zones using the data that has been collected.

In [[mode choice]], trips are assigned to a mode (usually auto or transit) based on what's available in a particular zone, the characteristics of the household within that zone and the cost of the mode for each mode in terms of money and time. Since most trips by bicycle or walking are generally shorter, they are assumed to have stayed within one zone and are not included in the analysis. Finally, in route assignment, trips are assigned to the network. As particular parts of the network are assigned trips, the vehicle speed slows down, so some trips are assigned to alternate routes in such a way that all trip times are equal. This is important because the ultimate goal is system-wide optimization, not optimization for any one individual. The finished product is traffic flows and speeds for each link in the network.<ref name="Johnston"/>

Ideally, these models would include all the different behaviours that are associated with transport, including complex policy questions which are more qualitative in nature. Because of the complexity of transport issues, this is often not possible in practice. This results in models which may estimate future traffic conditions well, but are ultimately based on assumptions made on the part of the planner. Some planners carry out additional sub-system modelling on things like automobile ownership, time of travel, location of land development, location and firms and location of households to help to fill these knowledge gaps, but what are created are nevertheless models, and models always include some level of uncertainty.<ref name="Johnston"/>

The post-analysis phase involves plan evaluation, programme implementation and monitoring of the results. Johnston notes that for evaluation to be meaningful it should be as comprehensive as possible. For example, rather than just looking at decreases in congestion, MPOs  should consider economic, equity and environmental issues.<ref name="Johnston"/>