For comparison, in the UK there are around 8 trains per hour during peak times between London and Cambridge (around twice the distance of DC-Baltimore). I'd imagine there are cities that have even more per hour in central Europe.
Comparing trains from London is not really fair because virtually every train in the south ends up in London eventually. Somewhat tragically, I once tried to take a train from Watford to visit Hatfield House, some 14 miles away. I think it took me 3 hours getting in and out of London :-)
OTOH between Macon (pop 34000) and Lyon (pop 500000) there is up to 4 trains / hour at commute times (1 an hour otherwise), over a slightly longer distance.
You really have to look at the metro population.