Under a federal administrative regulation, German road authorities work with an Unfallkommission, an accident commission. In North Rhine-Westphalia its permanent members are the road traffic authority, the road construction authority and the police. The commission must observe the development of road accidents continuously. When accidents cluster at one place within a set period, the place becomes an Unfallhäufungsstelle, an accident cluster spot. The commission then decides on measures to remove the factors that favor accidents. The measures must be suitable, appropriate and enforceable. Afterwards the commission checks whether they worked.