"Mind the gap" is a common phrase used in subway systems to remind passengers to be cautious of the gap between the train and the platform when entering or exiting the train. However, it is not typically used as a reminder when entering the ticket gate. The ticket gate area usually does not have a gap that poses a safety risk.
Instead, when entering the ticket gate, it's more common to see signs or announcements reminding passengers to have their tickets ready, ensure they have sufficient fare, or follow any specific instructions for ticket validation or entry. These reminders aim at the ticket gate to ensure a smooth and efficient flow of passengers through the ticketing process.