Final answer:
In Ontario, railway crossings on public roads are marked with yellow X signs, which serve as a universal warning to drivers to be cautious when approaching a railway crossing.
Step-by-step explanation:
Railway crossings on public roads in Ontario are marked with yellow X signs. These signs are used to warn drivers that they are approaching a railway crossing and should exercise caution. The yellow X is a universal traffic sign, making it recognizable to not only locals but also individuals who may be driving in Ontario from other regions.