Modern Models

In the environmental world, transportation models occasionally get a bad rap. However, if enough time is spent weighing the various factors that are incorporated in these models, the product can be extremely useful. Modern transportation models have a lot to offer in an environmental and economic context, as they depict much more than traffic and busses.

At the 91st Annual Transportation Research Board Meeting, held in Washington, DC last week, I outlined this idea in my presentation “What Model When?” as part of the subset, “Using Models to Meet the Demands of Transportation Planning in the 21st Century.”

Transportation models can be crafted to answer questions ranging from “What will the traffic be on this street if a new office building is built?” to broad scenarios like “What would the impact to housing and jobs be if we implemented a transportation greenhouse gas reduction plan?”

When choosing the right type of model to use, factors, such as geographic scope, granularity (level of geographic detail), number of input variables and the interaction between them, the model’s time scale and the use of feedback must be known. Of course, the complexity and sophistication of the model must be balanced against the time, money, data and technical skills you have available.

Often, problems arise from a misunderstanding of what the model reflects. A high level (or sketch planning) model explains the broad relationship between variables.

For example, the total amount of energy that could be saved if 10 percent of people switched from cars to bikes?

  • The sketch model is used to decide how many people we want to switch to bikes

For example, how many people might switch to bikes if a network of 25 miles of bike lanes is built on specific streets?

  • A complex travel demand model reports whether specific actions can get us to those results
  • The travel model is used to consider how to actually get them to switch

Models can also be linked to try to predict what the effect of transportation actions and policies might be on how a city grows, creates jobs or pollutes the environment. It’s an exciting time for transportation policy and new models can help us make the right decisions as long as we know how to use “What Model When.”

To check out the entire presentation, click here.

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