Home > Transportation planning

Transportation planning historically has followed the Rational Planning model of Defining Goals and Objectives, Identifying Problems, Generating Alternatives, Evaluating Alternatives, and Developing the Plan. Other models for planning include Rational actor , Satisficing, Incremental planning , Organizational process , and Political bargaining .

1 Forecasting

Within the rational planning framework, transportation forecasts have traditionally followed the sequential four-step model or urban transportation planning (UTP) procedure, first implemented on mainframe computers in the 1950s at the Detroit Area Transportation Study (DATS) and Chicago Area Transportation Study (CATS).

The four steps of the classical urban transportation planning system model are:

• Trip generation determines the frequency of origins or destinations of trips in each zone by trip purpose , as a function of land uses and household demographics, and other socio-economic factors
• Trip distribution matches origins with destinations, often using a gravity model function, equivalent to an entropy maximizing model. Older models include the fratar model.
• Mode choice computes the proportion of trips between each origin and destination that use a particular transportation mode. This model is often of the logit form, developed by Nobel Prize winner Daniel McFadden
• Route assignment allocates trips between an origin and destination by a particular mode to a route. Often (for highway route assignment) Wardrop's principle of user equilibrium is applied (equivalent to a Nash equilibrium), wherein each traveler chooses the shortest (travel time) path, subject to every other driver doing the same. The difficulty is that travel times are a function of demand, while demand is a function of travel time.

After the classical model, evaluative decision criteria are applied. A typical criterion is benefit-cost analysis. Such analysis might be applied after the network assignment model identifies needed capacity: is such capacity worthwhile? In addition to identifying the forecasting and decision steps as additional steps in the process, it is important to note that forecasting and decision-making permeate each step in the UTP process. Planning deals with the future, and it is forecasting dependent.

2 Precursor steps

Although not identified as steps in the UTP process, a lot of data gathering is involved in the UTP analysis process. CensusA census is the process of obtaining information about every member of a population (not necessarily a human population). It can be contrasted with sampling in which information is only obtained from a subset of a population. As such it is a method used f and land use data are obtained, and there are home interview surveys. Home interview surveys, land use data, and special trip attraction surveys provide the information on which the UTP analysis tools are exercised.

Data collection, management, and processing; model estimation; and use of models to yield plans are much used techniques in the UTP process. In the early days, census data was augmented that with data collection methods that had been developed by the Bureau of Public Roads (a predecessor of the Federal Highway Administration ): traffic counting procedures, cordon “where are you coming from and where are you going” counts, and home interview techniques. Protocols for coding networks and the notion of analysis or traffic zones emerged at the CATS.

Model estimation used existing techniques, and plans were developed using whatever models had been developed in a study. The main difference between today and yesterday is the development of some analytic resources specific to transportation planning, in addition to the BPR data acquisition techniques used in the early days.