Scenarios Developed for Improved Sustainability of Illinois Tollway

Abstract

This paper quantifies the environmental improvements in current versus past pavement materials and construction practices employed by the Illinois State Toll Highway Authority (tollway authority). Improvements in sustainability performance were measured with a life-cycle assessment (LCA) approach. Three scenarios were generated to evaluate tollway authority practices on the basis of eight 2013 Interstate reconstruction and rehabilitation projects. The first scenario, 2013 projects, analyzed the actual pavement material and designs of the 2013 projects. The second scenario, materials baseline, was based on the 2013 projects but modified to include mix designs with less-sustainable materials used by the tollway authority circa 2000. The third scenario, design and materials baseline, considered both mix designs and pavement design practices used circa 2000. To improve the spatial and temporal relevance of the analyses, two regional databases of life-cycle inventories representing processes from 2013 and 2000 were developed and applied to the 2013 projects and 2000 baselines. A tool developed by the Illinois Center for Transportation (ICT) of the University of Illinois at Urbana–Champaign, the pavement ICT-LCA 0.95, was used to evaluate the sustainability performance indicator (SPI), global warming potential (GWP), and cumulative energy demand (CED) for each scenario. The resultant savings in SPI, GWP, and CED from the first scenario ranged between 17% and 28%, 12% and 16%, and 13% and 26%, respectively, compared with the second scenario, and 12% and 33%, 8% and 26%, and 11% and 32%, respectively, compared with the third scenario.