TDM readind

• Urban transport planning started in the United States in the 1950s with the Detroit and Chicago Transport Studies, and was used to inform decision-makers on the transport system
• Urban transport planning


  Analyses the transport system, gives forecasts on future performance of the system and suggests measures to improve this performance in order to meet the desired level
• The rise of urban transport planning included the start of the development of transport models, as they are an essential component of urban transport planning
• Development of transport models

  • Theoretical framework was developed, compatible with economic theory, providing a justification and clarification of methods that were originally proposed on practical grounds
  • Major increase in computing power made it possible to analyse problems with a significantly larger scale and level of detail
• Urban transport planning process

  1. Definition

  2. Projection

  3. Constraints

  4. Options

  5. Formulation

  6. Testing

  7. Evaluation
• Pre-analysis phase


  Identification of problems, definition of goals and objectives, data collection, generation of alternatives

  
• Technical analysis phase


  Prediction of traffic flow on the links of a specified network using forecasting techniques, consisting of 4 stages: trip generation, trip distribution, modal split, traffic assignment
• Post-analysis phase


  Evaluation of alternatives, decision making, implementation, monitoring
• Model


  A (simplified) representation of a part of the real world - the system of interest - which concentrates on certain elements considered important for its analysis from a particular point of view
• Analytical models


  • Attempt to replicate the system of interest and its behaviour by means of mathematical equations based on theoretical statements
  • Value limited to a range of problems under specific conditions
  • Can be used for forecasting but subject to bias
• Continuous transport planning process

  1. Formulation of the problem

  2. Collection of data

  3. Construction of analytical model

  4. Generation of solutions

  5. Forecasting of future values

  6. Testing of model and solutions

  7. Evaluation of solutions and recommendation of plan/strategy/policy
• Formulation of the problem

  1. Data collection

  2. Construct analytical model and calibrate

  3. Generate solutions for testing

  4. Forecast planning variables

  5. Test model and solution

  6. Evaluate solutions and recommend best one

  7. Implement solutions
• A framework for rational decision making with models
• Transport system


  Complex set of relationships between the demand, the locations they service and the networks that support movements
• Transport systems


  • Mainly dependent on the commercial environment from which are derived operational attributes such as transport costs, capacity, efficiency, reliability and speed
  • Closely related to the development of transport networks, both in capacity and in spatial extent
  • Evolving within a complex set of relationships between transport supply, mainly the operational capacity of the network, and transport demand, the mobility requirements of an economy
• Transport is a service that must be utilized immediately and thus cannot be stored
• Mobility must occur over transport infrastructures, providing a transport supply
• In several instances, transport demand is answered in the simplest means possible, notably by walking
• In some cases elaborate and expensive infrastructures and modes are required to provide mobility, such as for international air transport
• Transport supply


  Expression of the capacity of transport infrastructures and modes, generally over a geographically defined transport system and for a specific period of time
• Transport demand


  Expression of the transport needs, even if those needs are satisfied, fully, partially or not at all
• Passenger-km


  Common measure expressing the realized passenger transport demand as it compares a transported quantity of passengers with a distance over which it gets carried
• Ton-km


  Common measure expressing the realized freight transport demand
• Transport demand is generated by the economy, which is composed of persons, institutions and industries and which generates movements of people and freight
• Layers of the transport system

  • Travel patterns of travellers and goods
  • Transport services, for enabling the movement of travellers and goods, using different transport modes
  • Traffic services, for enabling the movement of transport modes through physical infrastructure and management and operations of the infrastructure
• Consumer travel behaviour


  An individual will select a bundle of goods over all affordable bundles if it yields the greatest utility (i.e. satisfaction)
• Demand for travel


  Derived demand, as it is generated by the desire to join in activities, and generally not by the desire just to travel
• Supply curve


  Expresses the quantity of a given good that will be supplied or produced as a function of the price of the good
• Equilibrium


  Point where the quantity demanded is equal to the quantity supplied
• It is assumed that there will also be equilibrium within a transport system, or at least it will arrive in such a state after being left undisturbed for some time
• The quantity demanded is equal to the quantity supplied
• If shifts in demand and supply curves do not occur


  Markets can be expected to move towards the equilibrium point
• How markets move towards equilibrium

  1. If demand is higher than supply, prices rise due to "bidding up" of customers

  2. This stimulates an increase in supply and a decrease in demand, driving the market to equilibrium

  3. If supply is higher than demand, prices fall, stimulating a decrease in supply and an increase in demand
• There will of course be disequilibria due to, for example, traffic accidents, but these will always be transient
• It is difficult to compare the units of travel for demand and supply
• For demand, the units are counted in number of trips or distances, while for supply the response of the system is related to volumes of traffic at different places and times
• What happens when a shift in the supply curve occurs (from supply 1 to supply 2)

  1. A 'new' equilibrium point will be found following the same mechanism set out above

  2. The 'newly' derived travel demand (on top of the already 'revealed' demand) is often called the 'induced' demand

  
• In modelling, besides general modelling issues, aggregate or disaggregate modelling is discussed
• In modelling, there also has to be chosen if cross-sectional or time series data are used, and revealed or stated preference data
• The roles of theory and data are important in modelling