A driver warning system automatically detects the existence of in-the-road, passable obstructions and provides timely notification to a driver in proximity of such an in-the-road, passable obstruction prior to it being encountered with sufficient warning time for the driver to avoid the in-the-road, passable obstruction. To detect in-the-road, passable obstructions, the warning unit of a driver whose vehicle hits an in-the-road, passable obstruction will automatically generate a signal that is indicative of the existence of the in-the-road, passable obstruction and its location. This signal may be transmitted to a server, which contains a database of located obstructions. The collected information about the detected in-the-road, passable obstructions are provided to various warning units, so that they, knowing the driver location, e.g., based on global positioning system (GPS), can provide the driver with a warning of any upcoming in-the-road, passable obstructions with sufficient lead time for the driver to avoid hitting the obstruction.