Railroad crossing signals are divided into two categories: active and passive. Active signals warn drivers and pedestrians of oncoming trains, and passive signals alert people to the presence of railroad crossings or railroad tracks.
Active railroad signals warn drivers and pedestrians of approaching trains. They are activated manually or when the train passes over a special detection circuit. Active warning signals include flashing lights, bells, horns and automated gates. Passive railroad signals alert others to the presence of a railroad crossing or railroad tracks. This includes signs posted on or near the crossing along with any pavement markings near the crossing.