How frequent must passenger rail (not subway, nor elevated rapid transit) be at a minimum?

When any transit runs less frequently than a certain threshold (the minimum required frequency), then ridership suffers leading to service cuts and then a further loss of passengers - a transit death spiral. Leaving aside rapid rail transit (metro-style), what is the minimum frequency at which passenger rail ridership does not suffer.

I would say a general schedule of anything less than 60 minute headways is a deal-breaker. Peak time of 30 mins would be minimum as well.

That is such a highly dependent on circumstances number that consultants can specialize in answering it. In dense areas such as Tokyo and London, some routes can be daily (although every station served by that service may have other routes), while others can be peak schedule only, with no services outside peak hours.

To pick on a US example, the MARC Brunswick line services have not experienced a transit death spiral, but there are only 9 trains a day in each direction, all at peak hours in the direction of the peak commute.

I have trouble following the first paragraph of your comment because there is a open bracket but no closing bracket.

RandallW wrote: ↑Thu May 09, 2024 7:24 pm To pick on a US example, the MARC Brunswick line services have not experienced a transit death spiral, but there are only 9 trains a day in each direction, all at peak hours in the direction of the peak commute.

Could that be because the the MARC Brunswick line services are specifically tailored for peak commutes?

A useful (albeit very rough) rule of thumb is that the service should be at least as frequent as the length of the average passenger trip in order to be broadly useful, rather than only attracting only those peak-hour riders who are willing to accept limited frequency. A bus route where most passengers only ride a few stops needs to be very frequent to be useful, since a wait of more than a few minutes becomes a major factor in the amount of time passengers must set aside to make the trip. A commuter rail service with average passenger trips of an hour will be most useful if it runs at least hourly, while a long intercity service with average travel times >12 hours can still provide a useful service with one or two trips a day.

Myrtone wrote: ↑Thu May 09, 2024 8:36 pm I have trouble following the first paragraph of your comment because there is a open bracket but no closing bracket.

Sorry. I've corrected that.

Myrtone wrote: ↑Thu May 09, 2024 8:36 pm

RandallW wrote: ↑Thu May 09, 2024 7:24 pm To pick on a US example, the MARC Brunswick line services have not experienced a transit death spiral, but there are only 9 trains a day in each direction, all at peak hours in the direction of the peak commute.

Could that be because the the MARC Brunswick line services are specifically tailored for peak commutes?

I think that is the case (and has been for decades).

RandallW wrote: ↑Fri May 10, 2024 4:20 am

Myrtone wrote: ↑Thu May 09, 2024 8:36 pm I have trouble following the first paragraph of your comment because there is a open bracket but no closing bracket.

Sorry. I've corrected that.

Myrtone wrote: ↑Thu May 09, 2024 8:36 pm

RandallW wrote: ↑Thu May 09, 2024 7:24 pm To pick on a US example, the MARC Brunswick line services have not experienced a transit death spiral, but there are only 9 trains a day in each direction, all at peak hours in the direction of the peak commute.

Could that be because the the MARC Brunswick line services are specifically tailored for peak commutes?

I think that is the case (and has been for decades).

There are plans on the books to expand that service, but it requires an additional track, for long freights .

The EGE wrote: ↑Fri May 10, 2024 12:43 am A useful (albeit very rough) rule of thumb is that the service should be at least as frequent as the length of the average passenger trip in order to be broadly useful, rather than only attracting only those peak-hour riders who are willing to accept limited frequency. A bus route where most passengers only ride a few stops needs to be very frequent to be useful, since a wait of more than a few minutes becomes a major factor in the amount of time passengers must set aside to make the trip. A commuter rail service with average passenger trips of an hour will be most useful if it runs at least hourly, while a long intercity service with average travel times >12 hours can still provide a useful service with one or two trips a day.

Your comments are certainly valid for services (such as urban transport) meant for day trips, but I wonder if it is any different when the service is meant for those staying overnight between going one way and going the other way, as would be the case with a long intercity service with travel times of at least 12 hours.
Regarding buses (streetcars and light rail too) I do wonder if riding only a few stops per trip is less common where there is decent cycling infrastructure, bike lockers at railway stations and bike accomodation on trains, all of which displace short local transit trips.

Regarding buses terminating at railway stations, it also helps, depending on train frequency, to time buses to meet the trains. Each bus is timed to depart at or shortly after the designated departure time of a train due to serve the station.

As far as I can tell from skimming literature, good bike infrastructure decreases bus use (at least initially), but increases rail use. In a larger transport system with a rail backbone, this would be akin to replacing busses as the last mile transport to/from rail stations with bikes. All that said, maintaining the bus availability also encourages cycling--evening commute weather can be somewhat unpredictable at the morning commute, so a day that is predicted to be okay to cycle in both morning and evening may turn out not to be, and the bus becomes that alternate to cycling for that later trip, and on days when cycling isn't predicted to be safe, it's likely preferable (from a public policy perspective) for the bus is the alternative to cycling than that driving a car be the alternative.

But bike use is subjected to weather disruptions. Yes, buses with passengers for trains need to arrive before departure of same and leave after the trains discharge passengers. Plus there needs to be hard provisions delaying a bus for late trains and sometimes late buses for trains depending on how late and when next train due.

And a further complication arises when buses and trains are operated by different authorities, particularly if one of them is late.

ExCon90 wrote: ↑Sat May 11, 2024 9:09 pm And a further complication arises when buses and trains are operated by different authorities, particularly if one of them is late.

Absolutely. That is what I though about SO CAL proposal to start commuter rail. However it has done a good job of coordinating bus and Rail how not quite sure.