“…Consequently, the reliability and validity of many study outcomes may be challenged. Along with a handful of other examples (e.g., af Wahlberg, 2007;Stillwater and Kurani, 2011;Tulusan et al, 2012), we consider our experiment to be one of the few studies that investigates feedback on eco-driving under realistic driving conditions, with a larger sample size, a research design that is strong in causal inference, and an explicit reflection of important covariates (road attributes). Therefore, we call for future research to adopt our approach and even further increase the sample size to ensure validity of the research outcomes.…”