All over the world, transportation projects are changing how people and goods move, with direct and indirect impacts on greenhouse gases and criteria pollutant emissions. Transport and environment officials, investors and other stakeholders want to know, with different levels of accuracy and verifiability, how transport interventions will affect traffic, energy demand, and emissions.
Estimating the impacts of projects involving fuel or technology switch is conceptually straightforward but still with its challenges regarding the reliability of available data and the capacity for data collection. Projects affecting modal share, load factors, origin and destination patterns, number of passenger-kilometers driven, driving cycle and others parameters are an even more complex proposition. Without reasonable measurements of results, we are blind to the achievements we have promised ourselves.
This paper provides an overview of the challenges of estimating the impact of transport projects on CO2 emissions, describes how some key approaches and methods address these challenges, and provides illustrations with examples from cities in Asia and Latin America.