Limited role of judgment in project-level traffic forecasting

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# Appropriateness of Judgment

Deficiencies in data, unknown futures and irreconcilable differences between project options and available theory to model them are inherent to the traffic forecasting process. Professional judgment is often required to provide adequate traffic forecasts when the situation is not ideal. Professional judgment must be supported by both expertise in the forecasting technique and a high degree of personal integrity.

Any individual from an outside agency responsible for a project level forecast should hold a professional license in engineering (PE) or be a member of the American Institute of Certified Planners (AICP (opens new window)), be a faculty member in Civil Engineering or Urban Planning at a college or university in the United States, or have similar qualifications.

It is not possible to anticipate every situation when professional judgment might be necessary.

However, it is important to understand when professional judgment should not be used. Traffic forecasts must not be influenced by political considerations, conflicts of interest or any other factors that would lead to biases in the results. Traffic forecasts must not be made if the data and tools are insufficient for the task. Traffic forecasts must not be done in any manner that violates the canons of ethics of the Institute of Transportation Engineers (ITE (opens new window)), the American Institute of Certified Planners (AICP (opens new window)) or the American Society of Civil Engineers (ASCE (opens new window)).

# Asserting Parameter Values

Many forecasting techniques contain estimated parameters. All parameter values must be reasonable. If a parameter value is found to be unreasonable, it is permissible to “assert” a value of the parameter by adopting a value from one or more other studies where the parameter value is both reasonable and has been established to a good degree of certainty with well-regarded methods.

# References

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