Unmanned Aerial Vehicles (UAVs) are already in use by emergency services. Drones are becoming faster and more reliable, making them suitable for safety-critical tasks. A forerunner UAV can fly ahead of an emergency ground vehicle (EGV). It can make a decision on the traffic situation at the next intersection to notify the EGV driver if other vehicles have given the right of way or not. This notification service can increase the speed of the EGV and prevent crashes that may occur due to the driver's obstructed view. A forerunner drone for slow-speed EGV (10 m/s) has already been developed and successfully tested; however, the applicability of current drone technology to the forerunner task at higher speeds was not analyzed. This paper identifies the key parameters of the task itself and the forerunner system in a general case, and gives the main tradeoff inequalities of these design parameters. The requirements and limitations of a forerunner drone are investigated within a reasonable parameter space, and the most relevant configurations are tested in dynamic simulation using optimized velocity profiles for the drone. Software-in-the-loop tests were also performed in a complete city simulation. The results indicate that the forerunner task is solvable with current fastest or near-future drone technology if the route of the EGV is known to the UAV control.