These automatic warning devices are expensive and are primarily used at crossings with high vehicular traffic volumes. Time for the installation may take 12 to 18 months from field review to project completion. The majority of the money comes from the state government with the remainder coming from the federal or local government. The driver must treat the crossbuck as a yield sign and the motorist must stop whenever automatic signals are activated. Once the devices are installed, the railroad is responsible for maintenance costs.
Individual states decide which crossings warrant active warning devices.
Each state has a budget and uses its own formula to prioritize crossing improvements. Basically, nearly every type of active warning device for highway-rail grade crossings uses the rails to conduct the necessary electronic signal. As a train approaches a crossing, its wheels interact with a track electrical circuit. At a predetermined distance from the crossing, this interaction activates the crossing signals. First developed in the early 1870s, the simple DC track circuit is still used.