1. Assistant Professor, School of Planning and Dept. of Civil Engineering, Univ. of Waterloo, 200 University Ave. West, Waterloo, ON, Canada N2L 3G1 (corresponding author). E-mail: jcasello@fes.uwaterloo.ca
2. Professor, Dept. of Electrical and Systems Engineering, Univ. of Pennsylvania, 200 South 33rd St., Philadelphia, PA 19104. E-mail: tesmith@seas.upenn.edu