The environmental implications of transport planning and infrastructure have become an important consideration across the last decade. Significant research has been carried out to identify methods to reduce the impact of transportation systems, in particular surface transportation systems, on the environment. Transit signal prioritisation has been widely used throughout mass-transit systems to ensure schedule adherence and reduce delays for transit vehicles, primarily buses at a minimised cost to other vehicles on the network. However these systems do not take into consideration the impact on the level of emissions created by the signal prioritisation scenario. The paper demonstrates the emissions impact of a standard Transit Signal Priority (TSP) application simulated using the microsimulation tool, Paramics on the corridor network of El Camino Real, CA. Environmental performance data was collected using the emissions modelling tool "Paramics Monitor" and the results of the simulation indicate that even though emissions levels of busses reduce, the overall level of emissions tend to increase with the implementation of TSP. Accordingly the research study further proposes a methodology for the determination of real time transit signal prioritisation optimisation model with the primary aim to minimise the environmental impact (emissions and fuel consumption). In other words, this will in the future result in the development of an Eco-Transit Signal Prioritisation application. The provision of priority considers a number of parameters including the vehicle's location, speed, vehicle type as well as emissions (such as greenhouse gasses) and fuel consumption. In addition schedule adherence and the number of passengers on board also serve as important factors affecting both the level of emissions as well as delays experienced.