Don't try to flag down the train. Most engineers can effectively see about a half-mile ahead of their train. There's not enough time to stop by the time they see you flagging them down. Reflectors on rail cars quickly become ineffective because of dirt picked up by the rail cars when they're moving. Compliance and maintenance would be impractical because of the variations in sizes and shapes of rail cars combined with the fact that there are numerous owners of this equipment.
People also drive into the sides of trains in broad daylight.
Actually, about two-thirds of all collisions at crossings in the United States happen in the daylight hours. Flat spots on rail wheels are quite common and are caused when the wheels end up sliding on the rails for various reasons. Generally, there is no cause for alarm. It's like an automobile tire that wears unevenly, but isn't replaced until tread depth is reduced to a certain point. Railroad equipment is closely monitored by the railroads and by federal and state inspectors.