Q. Why are both subway stops at Penn Station set up so that the uptown and downtown express trains come in on the same platform, while the locals come in on side platforms? It makes it difficult to switch from express to local (or vice versa).

A. Those stops were built that way intentionally. Fearing the platforms would already be overcrowded from incoming railroad commuters, the designers wanted to coax passengers to switch between local and express trains at the Times Square — 42nd Street — Port Authority Bus Terminal complex, one stop to the north.

In fact, officials opened the first of those stops — which today serves the 1, 2 and 3 lines — earlier than planned, in June, 1917, “to handle the mass of traffic which passes daily to and from the Pennsylvania Station.” (The station serving the present A, C and E lines opened in 1932.)

For the same reason, the numbered lines at Atlantic Avenue — Barclays Center have a similar layout; riders can more easily switch at Nevins Street, one stop closer to Manhattan.