The Tocsen system consists of a smartphone app and a crash sensor which is mounted to the helmet of a cyclist. The system analyses a crash and calls for help in case of an emergency. The three-axis, 200g accelerometer and the sensors in the smartphone are able to detect a severe impact on the head and a movement profile which is characteristic of crashes in the user’s current activity. If the system detects a crash, an acoustic signal will sound and the app will ask if everything is all right. If the user does not react, Tocsen will send an alarm to the user’s personal emergency contacts, all Tocsen members nearby, and to the rescue coordination center (optional). GPS location and crash information will be shared to enable first responders and rescue teams to find the victim at the accident site and prepare them for the situation they will encounter.