“…Furthermore, many studies have investigated unit cost estimating relationships (CERs) between cost (dollar per lane length) and plan quantity or between cost and cost drivers for building and infrastructure construction using either statistical techniques or neural networks (Al-Tabtabai, Alex, & Tantash, 1999;Bell, 1987;Chengalur-Smith et al, 1997;Emsley, Lowe, Duff, Harding, & Hickson, 2002;Hegazy & Ayed, 1998;Herbsman, 1983;Jrade & Alkass, 2002;Lowe, Emsley, & Harding, 2006;Masi, 2003;Morcous, Bakhoum, Taha, & El-Said, 2001;Phaobunjong & Popescu, 2003;Saito et al, 1991;Sanders et al, 1992;Williams, 2005;Yu, 2006). Hegazy and Ayed (1998) developed a parametric cost estimating model for highway projects using a neural network approach, rather than using black-box commercial software.…”