Vehicle traffic management is becoming more complex due to increased traffic density in cities. Novel solutions are necessary for emergency vehicles, which despite growing congestion must be able to quickly reach their destination. Emergency vehicles are usually equipped with transmitters to control the traffic lights on their path and warn other vehicles with sirens. Transmitters are operated manually and, like sirens, have a limited range. Smart cities can make use of novel network models to facilitate traffic management. In this paper, we design a traffic management application leveraging software-defined network controllers for traffic preemption. The proposed application leverages the logical centralization of the SDN control plane to improve traffic management. Results from evaluating the application under five different scenarios indicate that emergency vehicles can reach their destination much faster, with very little effect on the surrounding traffic.