1. Topic

2. Introduction

The urban transportation system is very complex, and its performance depends on decisions made on many levels of society whose goals and purposes may be in conflict with each other. The process of evaluating, designing and managing such a system can therefore not be carried out without the aid of properly formulated models. In fact, over the past three decades, there has been growing interest in the ability of computer applications and simulation models for all aspects of transport operations, planning and management.

The choice of the Computer Simulation Systems (CSS) to be used in transport studies is governed by the objectives of the analysis as well as the available resources. A common classification method for CSS is based on the detail level with which the incorporated models suite intends to simulate the components of the transport system. According to this, CSS can be conveniently classified into four categories that reconcile the differences between alternative modelling concepts and theories, as well as between different levels of investigation in traffic and transport studies.

Starting at the most detailed (micro-) level, we have:

· Operational micro-simulation models that consider the characteristics of each individual vehicle and its interactions with other vehicles in the traffic stream;

· Tactical network models that are suitable for dynamic traffic effects analysis which are critical in network simulation during medium to congested flow conditions;

· Strategic Multi-modal transport models that are best suited to the urban-scale analysis of travel demand and transportation network performance;

· Land-use/transport interaction models that synthesise the dynamic interaction between transport provision and land-use activities.

3. Discussion

Land-use/transport interaction models packages are designed to analyse the fundamental, two-ways interaction between transport and land use. They offer a consistent representation of the way changes in transport costs and characteristics lead to changes in the demand for location and the intensities of activities and how these changes lead in turn to modified future demands for transport.

Actually, it is well known that trip-making patterns, volumes and modal distributions are largely a function of the spatial distribution of land use. Likewise the patterns of land use are influenced by the level of accessibility provided by the transportation system from one activity area to another.

These CSS describes land use by dividing up the study area into a number of discrete zones and stating how many units of different types of activity are located in each zone. They all describe development over time by representing the city at discrete points in time horizons (every 5 years in most models), so that the calculation refers to changes within each successive simulation period. Activities (people, houses, jobs) are allocated to each zone according to a function which measures the attraction of that zone for location, and which depends on accessibility of travel to other zones as well as on the particular attribute of the zone itself. Beyond these generalities, however the mechanism responsible for allocating land use and for representing travel vary greatly from one model to another.

The main characteristic of integrated land use and transport models is that the socio-economic inputs required by a transport model are provided by a land use model, instead of giving them as exogenous data. In turn, the transport model calculates a generalised cost of transport, which is fed back into the land use model.

4. Recommendation / Conclusion

The majority of land-use/transport interaction models applications answer traditional questions such as how land use regulations or housing programs would affect land use development and transportation, or how transportation improvements or changes in travel costs would shift the distribution of activities in an urban area.

Typical application phases for these models are the investigation on transport demand within urban or regional high level transportation and/or land-use planning.

Typical inputs are the land-use characterisation of the single cells (e.g. global or shared on age/activity basis population, availability of workplaces, amount of workers for each economic sector; etc.).

Of particular interest is the ability of such integrated models to provide useful inputs to the selection of travel-reduction strategies that will result in a net reduction in aggregate fuel use and emissions. Such reductions are usually thought of as resulting from one or more of the following five outcomes: 1) a reduction in the number of trip starts; 2) a reduction in the length of individual trips, through changes in destination; 3) a shift to either non vehicular or higher-occupancy modes of travel; 4) a reduction in the amount of travel during the congested, or “peak,” commuting periods; 5) a reduction in trip length and/or traffic congestion, through changes in route.

Concerning emission of pollutants, these models are suited to provide, purely as an indication, output data such as NOx (Nitrogen Oxides), CO (Carbon monoxide), HC (Hydrocarbons), PM (Particulate matter) emissions generally expressed in mass over a time period, ex. tons per day or tons per year in order to evaluate long term effects in terms of emission reductions achieved but are not able to evaluate dispersion of pollutants neither small scale effects.

5. Examples / Further Reading

An extended list of models within this category includes:

• CALIB (Mode Choice Modeling)
• HALLEY
• HLFM II
• MEPLAN
• MODE CHOICE
• SPF (Simplified Project Forecasting)
• TDC (Transportation Data Cruncher)
• TDM (Travel Demand Management Evaluation)
• The Highway Emulator
• TMOVES
• TRANUS
• UfosNET
• VISEM
• VISEVA
• WIVER

Further Examples:

6. Additional Documents / Web Links

A key investigation into the properties of land–use/transport interaction (LUTI) models was carried out in the latter part of the 1980s, under the auspices of the Transport Research Laboratory. The report of the investigation, known as ISGLUTI (International Study Group on Land–Use/Transport Interaction), has been published (Webster et al, 1990 “Land–Use Transport Interaction”). Nine candidate models were investigated in detail and, for seven of the models, their reactions to a series of policies was tested extensively against a wide range of appropriate indicators. The report summarises these and makes recommendations as to the way forward.

Also in the EU research project TRANSLAND (aimed at analysing innovative policies and future research needs in the field of integrated urban transport and land-use planning) a review of theoretical results from transport science, urban economics and urban geography as well as an overview of the state of the art in land use transport models including the work of the International Study Group on Land-Use have been carried out.

Further information on functionality and features of the above mentioned CSS are available at the following WEB site: www.meap.co.uk (MEPLAN), www.modelistica.com (TRANUS).

Other related references:

· University of Florida – Transportation Research Center – McTrans – http://www-mctrans.ce.ufl.edu/

· PTV AG – http://www.ptv.de/

Last Updated

25th January 2005