At which stop can a train arrive not more than 3 minutes early?

The answer is focused on the guidelines for train operations, specifically pertaining to early arrivals at stations. "D" stops, or designated stops, refer to stations where certain operational rules apply regarding train schedules and punctuality. The restriction that train arrivals cannot be more than 3 minutes early at "D" stops is established to ensure that operations remain predictable for passengers and to maintain the integrity of the schedule.

This regulation allows for a small buffer, recognizing that while trains can occasionally arrive early, a strict cap of 3 minutes helps manage overall service reliability. It also assists in coordinating connections and minimizing the potential for confusion for passengers waiting for trains.

Other types of stops, such as terminals or major junctions, may have different operational criteria regarding early arrivals, often focusing more on facilitating connections or turnaround times rather than the strict adherence to early arrival limitations. Therefore, "D" stops are specifically designated with this 3-minute early arrival rule to maintain punctuality and service stability.