For years, the RER A’s pride was that it was running 30 trains per hour through its central segment in the peak direction (and 24 in the reverse-peak direction). With two branches to the east and three to the west, it would run westbound trains every 2 minutes between 8 and 9 in the morning on the seven-station shared trunk line. Moreover, those trains are massive, unlike the trains that run on the Metro: 224 meters long, and bilevel. To allow fast boarding and alighting at the central stations, those trains were uniquely made with three very wide doors per side, and two bilevel segments per car; usually there are two doors near the ends of the car and a long bilevel segment in between. But now the RER A can no longer run this schedule, and recently announced a cut to 24 peak trains per hour. The failure of the RER A’s bilevel rolling stock, called the MI 2N or MI 09, should make it clear to every transit agency mulling high-throughput urban rail, including RER A-style regional rail, that all trains should be single-level.
On most of the high-traffic regional rail lines of the world, the trains are single-level and not bilevel. The reasoning is that the most important thing is fast egress in the CBD at rush hour. For the same reason, the highest-traffic regional rail lines tend to have multiple CBD stops, to spread the load among several stations. The Chuo Rapid Line squeezes 14 trains in the peak half-hour into Tokyo Station, its only proper CBD station, discharging single-deck trains with four pairs of doors per 20-meter-long car onto a wide island platform with excellent vertical circulation. Bilevels are almost unheard of in Japan, except on Green Cars, first-class cars that are designed to give everyone a seat at a higher price point; on these cars, there aren’t so many passengers, so they can disembark onto the platform with just two doors, one per end of the car.