As a followup to my claim that the Northeast Corridor in New Jersey had a more outer-suburban ridership than the Morris and Essex lines, I decided to tabulate the ridership distribution of various commuter lines. This tells you what percent of the ridership originates within some distance of the city center. All lines in New York are included, though some are grouped together because of branching.

Explanation: the ridership numbers for New Jersey Transit come from the New York Times, and those for the LIRR and Metro-North come from files published by the MTA. To maintain comparability with the Metro-North and NJT numbers, ridership in city terminal areas is ignored for calculation purposes; thus, X% really means X% of beyond-city ridership. This means stations from Jamaica west, from Newark Penn east, and from Harlem south are not counted. All km points are calculated from Penn Station or Grand Central, even for lines that do not run through to those stations. Finally, some lines are lumped together, when they share stations beyond the excluded city terminal zone.

Note that the data isn’t completely reliable. The NJT and Metro-North data sets paper this over by counting just one direction, but the LIRR counts both, and there are discrepancies, for example at Huntington. So the numbers above have a fair margin of error around them.

Observe that the ridership of the Northeast Corridor is so skewed outward that despite having twice the ridership of the Morris and Essex lines in New Jersey, the Morris and Essex lines actually beat it on ridership within 40 km of Penn Station. Similarly, the Harlem Line beats the New Haven Line up to 50 km.

Similar data exists in Boston, and, in harder to search form even if you speak the language, Tokyo (better data for Tokyo can be found here, but for most lines the numbers include only inner and middle segments, up to about 50 km outside Tokyo Station). It’s also quite easy in both cities to set a boundary of the excluded city zone, and with Boston this could allow constructing the same table.

The implication of the difference between various lines is that some lines are more local and some are practically intercity. This relates to the service decisions within each line – more stops or fewer stops – but there aren’t a horde of people in Elizabeth and South Newark who are clamoring to ride rush hour trains into Penn Station and would in large numbers if only stop spacing were narrower, or a horde of people in Sussex County who’d ride if only there were fewer stops between Dover and Penn Station.

That said, the more local lines do have potential for local service on trips that American commuter rail doesn’t serve. There’s an untapped market of people commuting from New Jersey to Jamaica and Brooklyn, or from Long Island to Newark and Jersey City, and this market necessarily needs to be served with more local trains, because most people in it live closer to the city.