A detection and warning system is provided for a railroad crossing. The system comprises a sensor configured to be mounted on an underside of a gate arm of a railroad crossing gate to detect a presence of a vehicle or other object that is obstructing the railroad crossing. The system further comprises a communication interface coupled to the sensor. In response to a detection of the vehicle or the other object, the communication interface to relay a warning signal indicative of a possible collision on the railroad crossing with the vehicle or the other object.