indicate an express service and double letters indicates locals. For example, the CC ran local and the C ran express on the Concourse and Eighth Avenue Lines. Unlike the IRT labels, the IND letters no longer follow the original pattern; the uptown branches of the B and C services have been switched via a complex process that involved the former AA eventually becoming the C and the B moving to the Concourse Line. Again, major changes have been made at the Brooklyn end (and in downtown Manhattan), but the system was designed for flexibility on that end. Unification and post-unification BMT/IND service label integration When all three systems came under city ownership in 1940, essentially nothing was done to standardize signage for two decades. Stations on the IRT and BMT still said Interborough or BMT Lines or sometimes older designations. Services continued to be signed by their traditional methods for each system. IND and post-Second World War ("R-type") equipment used BMT numbers when operating on BMT services. With the introduction of R12 equipment on the IRT in 1948, IRT subway services (except for the 42nd Street Shuttle) began using the route numbers still used today, which had been used internally but not on trains or maps. Astoria Line trains were only signed as 8 for a year, after which the line, which had been shared with the BMT, was converted for BMT operation only (and the Flushing Line carried only IRT trains). In 1960, with the delivery of the first R27 class cars for the BMT, the New York City Transit Authority (TA), which had become the operator of the combined system in 1953, began the introduction of letters for BMT services in anticipation of integrating the BMT and IND operationally. The last IND letter used was H, and the letter I was skipped as being too similar to the number 1. The BMT Eastern Division services got the letters J, K, L and M. The BMT Southern Division services were designated N, Q, R and T. P was for some reason skipped over, and while one theory says this was because it might lend itself to bathroom humor, the letter's undesirability for this reason would seem to be disproven by the fact that the letter was later proposed for an emergency line that would replace Long Island Rail Road service to Penn Station in the event of a strike,