Global acceleration of vehicle use is also accelerating highway construction. Expansion and maintenance of highway transportation systems rely upon the manufacture of cement, which, at every stage of the process, takes a toll on the environment. Generally, cement manufacture disrupts biodiversity across ecological spaces by the extraction of fuels and raw materials such as limestone, coal, and petroleum, which further contributes [Page 206]to greenhouse gas production. Beyond the damage caused by the manufacture of cement, its use as a material in highway construction also has severe implications for the environment. In contrast, emerging green highway concepts and innovations facilitate highway transportation system solutions that are ecologically sustainable. Green highway thinking is evident at the federal, state, and local levels, with highway agencies researching and implementing ...