Several factors may impact the reliability of information from the railroad signal system due to limitations inherent in railroad warning systems. The termination shunts are placed a set distance from the grade crossing based on the train’s maximum approach speed and the requested total approach time. Long approaches add complexity to the railroad warning system especially when approaches overlap with adjacent crossings. Additionally, when an environmental factor is introduced that causes varying train speeds, a consistent warning time becomes more difficult to replicate. Various factors include, but are not limited to:

Multiple tracks at the grade crossing,
Accelerating or decelerating trains,
Train stations near the crossing, and
Train yards and switching trains near the grade crossing.