It is well known that a significant amount to passenger trip activity involves multiple modes, destinations and trip purposes. For example, with multi-worker households, we observe a car commuter taking a child to a child care centre en route to work and also dropping their partner off at another location such as a railway station. This example is one of many trip chain configurations that represent the complexity of travel activity, and which have important implications on how we represent travel demand in transport planning models. What is not well understood is the impact that trip chaining has on greening the demand chain. We are unaware of any studies that have investigated the greening of passenger demand chains associated with the complexity of trip chains. This chapter uses the Sydney Household Travel Survey and an econometric model to identify the impact that the changing nature of trip chains has on CO2 emission. Results suggest that trip chains were stable in Sydney over a period of 15-year from 1997/98 to 2011/12. Emissions saving from chaining multiple activities into a single chain were found to vary between 5 and 19 % depending on whether the mode of travel is car, bus, or train.