Signal lights are essential for maintaining the operational efficiency and safety in urban road networks. Operational efficiency and safety at intersection have been two important topics in transportation science. In this study, the authors propose a car-following model to investigate the impacts of signal light on driving behaviour, fuel consumption and emissions during the whole process that each vehicle runs across the intersection. In particular, the proposed model has explicitly considered the behaviours at an intersection with countdown device that provides instantaneous information to drivers. The proposed model is tested by numerical analysis and the results indicate that the model can enhance the operational efficiency and the traffic safety near the intersection, and also reduce the average fuel consumption of the vehicles. Sensitivity analysis indicates that the vehicles' initial time headway at the road origin may have major influences on the flow capacity and the total fuel consumption.