Past eco-driving research has looked at the effectiveness of various eco-driving programs, but the role supervisor and organizational support have remained unexamined. This is unfortunate, as support from the supervisor and the organization have consistently been shown to determine whether or not employee interventions (e.g., training, safety) are effective (e.g., Christian et al. 2009; Salas et al., 2012). In other words, supervisor and organizational support are important for translating employee knowledge into actual behavior. Further, organizational resources for interventions such as an eco-driving program may be wasted if supervisors and managers do not demonstrate their support for it to employees. Thus, the goal of the proposed study is to examine not only whether an eco-driving program changes employee attitudes, knowledge, behaviors, and fuel use, but how to ensure that the program is effective. The Oregon Department of Transportation (ODOT), as part of the Oregon Sustainable Transportation Initiative (OSTI), created EcoDrive to provide marketing, educational materials, and training regarding eco-driving to fleets of light-duty vehicles. EcoDrive was professionally developed. Based on our preliminary study of EcoDrive in three public sector organizations, including interviews with fleet managers and with survey data collected at 3 time points, we found that the introduction of materials from the EcoDrive program (e.g., posters into the workplace, cling stickers onto windshields, videos) was associated with some change in employee eco-driving knowledge, but little change in self-report eco-driving behavior for the sample as a whole. However, for employees who perceived high supervisor support, there was a significant improvement in eco-driving behavior. Based on these preliminary data and their interpretation, we propose to expand the implementation of the program in 3 ways: 1) Provide training for supervisors and managers to help them support the eco-driving program and demonstrate their support to employees. This is based on a tested supervisor training program designed to provide support to employees (e.g., Hammer et al., 2011). 2) Use a control group of employees whose supervisors do not participate in the training as a comparison. 3) Assess fuel use more precisely and track the use of fuel in individual vehicles.