A collision warning device for motor vehicles includes: a locating system for locating objects in the area in front of the vehicle; a control device for evaluating the data of the locating system and for outputting a warning signal in the event of an imminent risk of a collision; and a detection module for detecting the course of guardrails with the aid of the data of the locating system. In the control device an additional warning function is implemented, which calculates, with the aid of the dynamic state of the vehicle and with the aid of the detected guardrail course, a parameter for the transverse dynamics of the vehicle, which is required to avert a collision with the guardrail, and which outputs a warning signal when this parameter is larger than a predefined value.