Mind the gap

Scholars at the University of Amsterdam found a gap between models and reality in urban transport planning, and decided to host a conference addressing the discrepancy. From 14 to 16 October 2009 they will bring together PhD students, leading scholars and practitioners – both model developers and urban planners – all of whom have dealt with, or are currently dealing with, bridging the gap.

What causes the gap? Sometimes models oversimplify reality, while on other occasions theory is so complex that implementation is impossible in reality.

Programme
The 14th is for PhD candidates only. They are invited to submit their proposals now. In an international workshop on this day eight young PhDs will have the chance to present their work to fellow PhDs and senior researchers and discuss their work with them.

On 15-16 September the actual public seminar will take place. Day two falls under the header Science meets practice: scientific presentations with references from practice, while the third and last day is titled Practice meets science: best practices with references from science. For a list of experts and companies present, see the programme.

Highlight: Michael Wegener - From Macro to Micro

'The more micro the merrier' is not always true, states Michael Wegener of urban and regional research company Spiekermann & Wegener in Dortmund, Germany.

Michael Wegener will deliver the keynote address on 15 September. He will warn against taking the trend of disaggregation in urban transport and land use modelling too far.

At first sight disaggregate models seems to fit the ongoing tendency in society towards individualisation. Mobility patterns have become so diversified, that generic models can hardly capture them. Also, models nowadays need to include environmental issues, such as air quality, noise, landscape and water, which is difficult in simplifying models.

But disaggregation has a price. Not only can data requirements and computing times of these models be enormous, there are several more fundamental problems:

• Disaggregate models are too slow to examine the multitude of scenarios needed to formulate policies.
  
• The results of microsimulations can vary significantly between model runs with different random number seeds, unless averaged to a level of aggregation they were designed to overcome.
  
• For environmental reasons and because of future energy scarcity, transport may become significantly more expensive. Mobility will then reflect basic needs and constraints rather than individual preferences.

Balancing is the answer: to develop models with just the right, minimum amount of simplification. Wegener prefers multi-scale models. He will conclude his presentation showing an example of a multi-scale land use, transport and environment model ranging from the European to the grid-cell level.