15 minutes off-peak

[stephenk]

Most of us think that a 15 minute off peak inner suburban service would make public transport much more attractive in Brisbane. I decided to have a look at the practicalities of running an off-peak 15 minute service, based on the current service patterns.

Ferny Grove Line - The single track section has a 10 minute frequency constraint. This would still allow for 15 minute services with 5 minutes of operating margin. The extra services required for a 15 minute service could be slotted into the existing timetable by utilising both of the platforms at Ferny Grove.

Cleveland Line - Due to the single track sections the Cleveland Line cannot quite support a 15 minute service to Cleveland. However a 15 minute service to Manly could be slotted into the existing timetable. The service would either have to wait 2 mins to enter the Down platform, with a 13 minute dwell time. Or it could reverse in the single track section beyond Manly (if the signalling allows) with a 15 minute turnaround time.

Ipswich Line - Already runs a 15 minute off-peak service weekdays to Corinda. A 15 minute weekend service should be added. The alternate service could reverse at Richlands when it opens. 

Beenleigh Line - Now despite having 3 tracks for much of it's route, this could be more problematic, and would require significant timetable alterations. Trains leave Beenleigh 6 mins after the Gold Coast service, and arrive at South Bank 7 mins before the next Gold Coast service (a 17min journey time saving). Running a 15 minute Beenleigh line service (irrespective of terminus) would get in the way of the Gold Coast service. Not a problem, there's  third track I hear you say. However the overtaking would have to occur at Coopers Plains. This is also where both services would pass, in both directions at the same time. Last time I checked Coopers Plains didn't have 4 tracks! Thus some considerable timetable re-jigging would be required to allow Gold Coast services to overtake using the third track, but in different locations. There is also the issue of the terminus for alternate services. Kuraby is the most suggested option as it has three tracks. With current dwell times at Beenleigh, this would only allow only a 7 minute dwell at Kuraby.  This could be extended if the turnaround time at Beenleigh was also extended, but it can only be extended by a few minutes as it already 25mins. Or the dwell time at Kuraby could be extended to 27 mins (max possible) by decreasing the Beenleigh turnaround to 15mins. The turnaround times would also have to fit in with the overtaking locations when devising the timetable. Maybe an alternative terminus would be better?

(Just of interest for the Tennyson fans amongst us, a train from Corinda to City via Yerongpilly could be fitted into the existing timetable 15mins behind the Beenleigh trains without delaying the Gold Coast service. However, this would only give a 15min frequency as far as Yerongpilly).

Shorncliffe Line - Since this line doesn't even have a 15min peak service yet, it's probably not the top contender for a 15min off peak service. With current infrastructure, a 15min service is possible with a max 10min dwell time at Shorncliffe. This would of course require rewriting of the Shorncliffe timetable, which currently has a 15min dwell at Shorncliffe.

Caboolture Line - Petrie is the most suggested terminus for alternate trains to create 15min service on the Caboolture Line as it has three tracks. With the current dwell time at Caboolture being 24 mins, would only give 4 mins turnaround at Petrie. So dwell times would either need to be extended at Caboolture (requiring 2 platforms), or reduced (15 minutes dwell at Caboolture = 25 mins dwell at Petrie).

Airport Line - The single track section only just about allows for a 15 minute service with little operating margin. A delayed Up service will this delay the next Down service. Thus a 15 minute service has to be based around this constraint.

Doomben Line - Flying pigs are more likely than a 15 minute Doomben service. Although just about technically possible with no operating margin, it wouldn't allow any freight trains to use the line with current infrastructure. I think the best the Doomben Line can hope for is either a 30 minute service, or more regular bus replacement.

Whilst some of the above could have 15min services added quite easily, it has to be remembered that that both ends of the line have to be taken into consideration, as well as other services sharing tracks through the core section. Thus the timetables would require quite a bit of rewriting. However a 15min off peak service is possible across most of QR Citytrain's inner suburban network.

Please let me know your opinions and suggestions on the above.

[albiwan]

So could the Shorncliffe trains terminate at Cornida via Tennyson either at 15 or twenty minute interval off peak?

[stephenk]

So could the Shorncliffe trains terminate at Cornida via Tennyson either at 15 or twenty minute interval off peak?

I think would it would be overkill. Tennyson doesn't even require 15min peak intervals, and Shorncliffe would only just about justify a 15min off-peak service service. It would also put a lot of pressure on the line via South Brisbane.

[Derwan]

I think the biggest constraint has nothing to do with the physical capabilities of running trains with 15-minute intervals on each line.  I think the biggest constraint is cost.

We're talking about effectively doubling the number of drivers and guards working during the off-peak period.  Add to this the more frequent maintenance required due to the additional running hours of every train.

It'd be great if it could happen - but perhaps we need to look at 20-minute intervals (3 trains per hour) as the next step - at least for some lines.

[ozbob]

Excellent thread and comment.

For interest, the now Deputy Premier has said in another life as Transport Minister that one of the goals is a broad 15 minute off peak frequency on the major lines during off peak.  I have modified that a little to the standard ambit claim of frequency of suburban services to be 15 minutes between 5am and 8pm Mon to Fri on all lines.  Peak times 7.5 minutes or better depending on load demands. Before 5am, after 8pm Mon to Fri, Sun Public Holiday 20 minute frequency on all lines.  Now this is broadly consistent with the preceeding discussion.
In many cases it is achievable within the constraints Stephen and Derwan have mentioned.

I think it was Jason who has suggested two stage approaches as well. Again I believe this is another suggestion with merit. That is running expresses services in from key intermediate stations.  Eg.  All stoppers Ipswich to Darra and return.  Express services from Darra to CBD (key station stops only). Other all stoppers Darra to CBD. With the quad track these variations are possible.  The down side of that is the need to change at Darra, although selected services could be straight through.  Just another idea.

There are variations possible than just building on the present patterns, point to point radial. We have of course discussed possible loop variations as well.  The answer my well lie in a combination of patterns to extract the highest utility from the now expanding resource - trains and crew.

Rail is going to be called upon to carry at least double it is present patronage within 5 years is my estimate. This is due to the changing transport habits as fuel and environmental costs start to bite, and population pressures as such.  Our bus system, although in many respects one of the best in the nation, is struggling and will continue be overloaded. There is a limit to the amount of buses that can continued to be put on our busways.  The real increase in capacity in the next period will be rail.  We can double capacity on rail without any major difficulty as pointed out in the thread above.  There will be more integration of bus with rail, an important task for the TransLink Transit Authority (amongst other things!).

Please keep the comments/discussion going.  This is the seed of a new era.

Regards
Bob

[stephenk]

I think the biggest constraint has nothing to do with the physical capabilities of running trains with 15-minute intervals on each line.  I think the biggest constraint is cost.

We're talking about effectively doubling the number of drivers and guards working during the off-peak period.  Add to this the more frequent maintenance required due to the additional running hours of every train.

It'd be great if it could happen - but perhaps we need to look at 20-minute intervals (3 trains per hour) as the next step - at least for some lines.

It is true that this would require extra staff, but it wouldn't require anywhere near double the staff. For starters, not every service is being duplicated, and many of the extra services would not run out to the outer terminus (saving a train and crew). At peak times some trains and (and thus crew) just do one out and back journey. Running 15 min off-peak intervals might thus use some of the existing staff more efficiently!

I actually think that QR should go straight to 15minute (4tph) services rather than 20minutes (3tph). I would expect that 15min frequencies are considerably more attractive to the public than 20min, even though there's just 5 mins difference. It would also make timetabling much harder to run 30min services on some routes, and 20mins on others. A 15 minute off-peak service would provide a backbone timetable for more frequent peak hour services (average of 7.5mins on some routes - although they wouldn't actually run at 7.5min it would be more like 6/9min alternating).

Express services from Darra to CBD (key station stops only). Other all stoppers Darra to CBD. With the quad track these variations are possible.  The down side of that is the need to change at Darra, although selected services could be straight through.  Just another idea.

There are variations possible than just building on the present patterns, point to point radial. We have of course discussed possible loop variations as well.  The answer my well lie in a combination of patterns to extract the highest utility from the now expanding resource - trains and crew.

With 15min (4tph) services there would be a lot of routing options. Personally I would try and keep things simple (i.e minimise the number of conflicting movements as at present) by running services on their current line groups e.g Ipswich/Caboolture/Shorncliffe and Ferny Grove/Doomben/Airport/Cleveland/Beenleigh/Gold Coast. I would not operate any loops, for reasons cited in other threads. For political reasons the Gold Coast services would probably have to be paired with the Airport service. Care would also have to be taken to not send too many trains via South Brisbane, which could get pretty saturated with off-peak services.

The extra services could allow off-peak express services on some parts of the network depending on line pairing e.g if 4tph were to run all stations to Corinda, then the 2tph Ipswich service could run express (with limited stops) between Corinda and Roma Street improving the journey time for travellers to Ipswich. If 4tph were to run towards both Shorncliffe and Petrie/Caboolture, then the Petrie/Caboolture trains could run express Northgate to Eagle Junction, and Eagle Junction to Bowen Hills, allowing the 4tph Shorncliffe train to run all stations. There are of course a lot of potential service combinations, which are also dependant upon which lines are given 4tph status.

Maybe a trial service with 15mins of busiest lines (Ipswich, Caboolture, & Ferny Grove) could be operated as:-
2tph Ferny Grove - Beenleigh
2tph Ferny Grove - Darra via Tennyson & South Brisbane
2tph Airport - Gold Coast
2tph Doomben - Cleveland
2tph Bowen Hills - Manly
2tph Caboolture - Ipswich
2tph Petrie - Corinda
2tph Shorncliffe - Roma Street
I know the above is far from a perfect solution, but would allow services to be slotted into the existing timetable based on current running and terminus dwell times. Most times for existing services would remain the same, but the Petrie - Corinda service would take the Shorncliffe services current slot, and the Shorncliffe service would have to have it's slot moved. Based on the existing timetable, the Darra-FG service would actually leave Darra 6 mins after the Ipswich - Caboolture service, allowing for an easier connection to access South Bank (and associated travel options).