Final answer:
Train operators use experience and training to know when to coast under normal conditions, combining knowledge of the train and route with real-time signals like crowd movements.
Step-by-step explanation:
Train operators generally know the points at which coasting should be used under normal conditions by experience and training. Both experienced and new train operators are trained to identify the optimal points for coasting, which considerably depends on the train's current speed, track condition, and the train's weight. They learn when coasting is efficient to conserve energy without impacting the schedule. Over time, they develop an instinctive understanding of the train's performance and the route, which allows them to make real-time decisions on when to coast. Additionally, regular monitoring of the rail traffic and intuitive knowledge of crowd movements can signal the operators if a train is running late or if there is a change in track, which further aids in decision-making.