A railroad crossing traffic warning system for alerting a motorist approaching a railroad crossing to the presence of an oncoming train. The system comprises a series of magnetometer sensor probes buried in the right-of way adjacent to a railroad track at predetermined distances from the railroad...http://www.google.fr/patents/US5735492?utm_source=gb-gplus-shareBrevet US5735492 - Railroad crossing traffic warning system apparatus and method therefore
Railroad crossing traffic warning system apparatus and method therefore
