until this time, with the exception of buses that replaced subway lines, it had been understood that overnight transit was provided by regular routes that happened to have 24-hour service. night services retained the same route names and numbers as their daytime counterparts, perhaps with a suffixed letter if there was a variation in the exact routing. but now a marketing decision was made to treat the overnight service as a new, distinct set of routes, even in those cases where the day route was identical.