The study of roadway sustainability in Texas : a case study with the use of the Greenroads rating system

In the state of Texas, the roadway network consists of approximately 313,228 miles of roads (Federal Highway Administration, 2013), accounting for 7.61% of the public roads in the United States. To put it in perspective, this is equal to 12.6 times the circumference of Earth. In order to manage this network, the state and local transportation agencies use millions of tons of natural resources to construct and maintain these facilities. If these resources are not being properly used, Texas might end up wasting them, producing more pollutants, and imposing threats to its natural environment. Moreover, there is no way to quantify and record the efforts made by the Texas transportation community in becoming sustainable. Thus, there is a need to promote and keep track of ongoing sustainability efforts. In this study, we explore the trend of roadway sustainability in Texas, and propose a Texas version of sustainability rating system that is based on Greenroads. The Greenroads sustainability rating system is a third-party rating system developed by the University of Washington and aimed at recognizing sustainable practices in roadway projects. First, two of its projects in Texas are selected as the case study for the purpose of understanding the system. Second, 1,594 pavement projects are extracted from Texas highway construction database called Site Manager that is maintained by the Texas Department of Transportation (TxDOT) to understand the state of practice. Third, some material data that comes from TxDOT division engineers is included as well. Together with them, a Greenroads-based sustainability rating system, especially adapted in terms of material selection and pavement technology, is proposed. As a result, the implementation of this system is expected to spark more pursuits of roadway sustainability in Texas.