Induced travel occurs when new roads or lanes are constructed with the aim of reducing traffic congestion. In practice, this often results in new travel filling the additional capacity, thereby negating the intended goal of congestion reduction. The phenomenon is fundamentally driven by economic supply and demand principles: increasing road capacity reduces travel time costs, which subsequently increases demand for road usage.
Despite this theoretical relationship being well-documented and supported by empirical research over decades, many methods for forecasting travel growth do not adequately account for induced travel. To address this gap, the New Jersey Induced Travel Calculator has been developed, modeled after a similar tool used in California (Volker & Handy, 2022). This calculator provides estimates of induced travel resulting from increased lane-miles or road capacity across all road types and counties in New Jersey, using empirical data from published literature.
The calculator also serves as a quality check for existing forecasts of increased travel. Environmental assessments of specific projects should include these forecasts; large projects typically require an environmental impact report under the National Environmental Policy Act. These documents inform decision-makers and the public about potential adverse environmental impacts and explore mitigation strategies. However, such assessments often overlook induced travel impacts in their traffic growth projections.
Considering induced travel is crucial as any increase in vehicle travel will likely raise greenhouse gas emissions. This could hinder New Jersey's objective to reduce greenhouse gas emissions by 80% below 2006 levels by 2050, with an interim target of a 50% reduction by 2030 (New Jersey’s Priority Climate Action Plan, March 2024). Failing to account for induced travel can also lead to an overestimation of project benefits regarding congestion reduction.
The calculator includes annual greenhouse gas emission estimates associated with capacity expansions. It aims to assist transportation planners and the public in better assessing project impacts by providing a range of estimates that help determine if forecasts align with expected outcomes.
The calculator is accessible at: Home | New Jersey Induced Travel Calculator (travel-calculator-henna.vercel.app).
References:
New Jersey’s Priority Climate Action Plan, March 2004
https://dep.nj.gov/wp-content/uploads/climatechange/nj_pcap_final-1.pdf
