Optimizing Road Gradients Regarding Earthwork Cost, Fuel Cost, and Tank-to-Wheel Emissions
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Original versionJournal of Transportation Engineering, Part A: Systems. 2020, 146 (3), . 10.1061/JTEPBS.0000289
Emissions reduction has emerged as one of the principal targets in the planning and designing of road alignment today, and intelligent design methods can help optimize road alignment as a response toward more sustainable road infrastructures. The largest share of emissions in road transport occurs in the use phase; hence, considering vehicles’ behavior already in the early stages of the planning process is crucial. This study compares earthwork costs, fuel costs, and tank-to-wheel emissions of alternative road vertical alignments using a spline linear programming (LP) optimization method. The traditional minimal earthwork cost model is tailored and augmented with a fuel item to account for vehicle fuel costs. Three options are considered, including an earthwork-based (EW) optimal road alignment, a balanced earthwork-and-fuel cost (EW-FC) optimal alignment, and a minimal fuel cost (FC) alignment. Calculations are done for a reference test heavy-duty vehicle assumed to operate at uniform speed. The results exhibited that, although leading to some increase in earthwork costs, a design for balanced EW-FC cost yields substantial fuel budget and related emissions savings.