Recent research questions whether motivation is practically relevant: that is, whether people's environmental motivation can be held accountable for their CO2 emissions. Using the highly emission-relevant mobility domain as our example case, we expound that environmental motivation is relevant for people's emissions. Its relevance can, however, be overlooked easily for three reasons. (A) People differ—irrespective of their environmental motivation—in their travel demands (i.e., the overall distance they travel). (B) Environmental motivation controls people's emissions exclusively indirectly by determining the likelihood of sustainable mode choices. (C) And environmental motivation's emission efficacy will be attenuated by the typical majority of comparatively short trips. Accordingly, only when we account for people's travel demand and only when people persistently choose sustainable modes of transportation for long-distance trips does the relevance of environmental motivations become more recognizable.
GPS mobility data tracked over the course of two weeks from 231 individuals were gathered, and, based on these data, people's emissions were calculated. In total, 18,745 trips were recorded. A linear regression analysis confirmed (A) that environmental motivation was, by and large, unrelated to people's travel demand. A mixed-effect Bayesian logistic regression corroborated (B) that environmental motivation reliably influenced people's sustainable travel mode choices. Finally, mixed-effect Bayesian gamma and linear regression analyses confirmed (C) that environmental motivation's emission-reducing efficacy strongly increased with increasing travel distance at the trip-level and overall travel demand. Essentially, we found environmental motivation to truly matter. This became recognizable when the emission-reduction potential is greatest: with long-distance trips and for people who travel more.