A number of metropolitan areas are confronted with the process of urban diffusion. Under such circumstances, metropolitan-wide urban activity location models are disrupted by this process and pose a challenge to a range of paradigms, particularly those that address the dynamics of mobility. Although a vast literature exists on the relationship between urban form and commuting, the issues that surround spatial reorganization are not clearly defined, and research findings contradict each other. At the same time, metropolitan environmental awareness is growing, leading to greenhouse gas emission inventories, climate change plans and policies to reduce metropolitan emissions. The question on the implications of the diffusion of activities at the metropolitan level on commuting patterns and thus on transportation greenhouse gas emissions can be raised. This paper offers new insights into this question by examining how the transportation sector can play a vital role in Montréal in contributing to the reduction of GHGs.