New Tool Calculates Induced Demand Caused by Road Widening Projects

The calculator can help transportation advocates and agencies project how many additional miles and emissions a highway widening project would create.

October 22, 2021, 8:00 AM PDT

By Diana Ionescu @aworkoffiction

Highway 520

oksana.perkins / Shutterstock

A new tool from nonprofit RMI and a consortium of partners including Transportation for America and the National Resources Defense Council "draws on formulas sourced from decades of proven scientific literature to deliver detailed, community-specific induced demand forecasts with the click of a button." The State Highway Induced Frequency of Travel (SHIFT) Calculator "gives advocates the tools they need to instantly show the real impacts of proposed highway expansions in their communities," writes Kea Wilson, providing a valuable resource for showing the real-world impact of the well-documented but poorly understood phenomenon of induced demand.

"Sustainable transportation advocates and forward-thinking professionals alike have known since at least 1932 that expanding highways to cure congestion almost always has the opposite effect," writes Wilson, but "many of them haven’t been able to quickly quantify exactly how much additional driving a specific project would encourage, or exactly how much all those new vehicle miles traveled will exacerbate the climate crisis — until now."

The tool comes at a crucial time, with billions of dollars for road funding promised in the federal infrastructure bill. The calculator's creators hope it will help state DOTs develop more accurate projections that show the true costs and impacts of road widening.

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