The investments made by transportation agencies are often guided by increasingly sophisticated models and forecasts, which strive to account for more factors and become more accurate in predicting travel patterns. These improvements, while promising for the future, also highlight the many ways that most agencies’ existing models miss the mark. Values-based decision-making can help agencies achieve the outcomes they have set out in their long-range plans more effectively than relying on models alone.
forecasting
USDOT could advance travel modeling and help planners account for induced demand
A provision of the Bipartisan Infrastructure Law (Sec. 11205) requires USDOT to review existing travel demand models and, among other things, consider the potential implications of induced travel. Federal officials, committed to that mandate, were at the TRB annual meeting last week to learn from modeling experts and practitioners. This blog post offers one perspective on the issues and lays out several opportunities gleaned through discussions at TRB.
How reliable are traffic forecasts?
As reliant on traffic forecasts as transportation agencies are to plan and design road projects, those forecasts are rarely evaluated to see how well they held up after project implementation. A massive new study, outlined in a recent NCHRP report, fills that gap. It compares traffic forecasts from 1,291 projects that opened since 1970 to actual traffic counts. Only 10 percent of the projects opened before 2003.
U.S. DOT: States overestimating VMT growth
The U.S. DOT recently released its 2015 Conditions and Performance Report to Congress, describing the current state and future needs of the country’s roads, bridges, and other transportation infrastructure. In this newest C&P report, U.S. DOT recognizes that its past forecasts were too high, adding, “states have tended to underpredict future VMT during periods when actual VMT was growing rapidly and to overpredict at times when actual VMT growth was slowing or declining.”
With trend towards road tolling, demand forecasting critical
As VMT decreases, forecasting demand and toll revenues for new projects is becoming increasingly difficult. DOTs should consider three new factors in traffic forecasting: first, how flat-to-declining VMT will affect revenues collected; second, how the presence of untolled parallel roadways will also impact toll revenue; and third, how driver value-of-time plays into roadway choice, also affecting toll collection.