Fluctuating fuel prices, rising congestion, longer commutes, and related environmental and human health effects have combined to once again draw the interest of policy makers, consumers, and firms toward the concept of travel demand management (TDM). While TDM is not new, the proliferation of mobile telephony, fixed Internet, and associated applications has created fresh prospects for the implementation of commuter focused TDM strategies. One recent example is Carpool Zone, an on-line carpool-matching tool deployed and managed by the TDM group at Metrolinx, which is responsible for the Smart Commute program. Metrolinx is the regional transportation planning agency within Canada’s largest metropolitan region, the Greater Toronto and Hamilton Area. Using data provided by Metrolinx, this paper broadens current thinking on carpool formation and use. The main hypothesis guiding this work is that the carpool formation and use process is sensitive to personal and household characteristics, space, time, travel cost, and workplace policies. Results from a logistic regression analysis suggest that geographical proximity to other users; workplace TDM policies; the scheduling of work; and role preference increase the odds of constructing an operational carpool. Importantly, findings regarding the positive influence of workplace TDM policies suggest that Internet based TDM interventions will likely require critically important investment in human capital at the “back-end” to ensure program participation.