The vulnerability displayed by lineal infrastructures, such as highways, is of special concern inside the existing landslide risk assessment methodologies. Their construction often implies the creation of cut slopes with a steeper angle than that displayed by the same material on natural slopes. This can result in landslides that affect the facility and its users. To establish the spatial and temporal probability of impact of landslides on vehicles, it is necessary to consider parameters related to traffic, the vehicle, and the cut slope itself. These parameters have to be realistic in representing the case analysed; otherwise the results will not reflect the risk. The methodology presented in this document includes factors normally used in traffic analysis, such as level of service, average travel speed and the volume of traffic on the 100th highest hour, to determine the probability of landslide impact to a vehicle on two-lane highways. The application to a particular cut slope located on a two-lane highway in Spain reflects the important role played by the probability of impact in the determination of the consequences related to landslides.