The Pros & Cons Of Branching And Its Alternatives

[M II A II R II K]

Branching


2012/10/24

Read More: http://pedestrianobservations.wordpress.com/2012/10/24/branching/


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Since branching is a service planning decision independent of technology, any technology could branch. The branching-friendliest technology is subway-surface: the central subway segment has higher capacity measured in trains per hour than the outer surface segments, and this requires branching. For examples, consider the Boston Green Line, Muni Metro, the Frankfurt U-Bahn, and SEPTA’s Subway-Surface lines.

- Even when rapid transit is built separate from both light rail and mainline rail, branching is useful for lines going into the suburbs or even outer-urban neighborhoods. This is practiced in both New York and London, both of which have extensive branching. Observe further that in both cities, the lines reaching farthest out – the A in the Queens-bound direction and the Metropolitan line in the west – are also the most highly branched.

- When lines do not branch, there must be a strong outer anchor, or else trains need to run empty outside the center. The alternative is short-turns, and if there’s no space for this, the resulting service patterns can be awkward. Shanghai, which has little branching, runs Line 2 in two segments, a central segment with higher frequency and longer trains and an eastern one with lower frequency and shorter trains; trains do not run through. Beijing has a similar awkwardness with the split between Line 1 and the Batong Line, and Toronto has a split between the Bloor-Danforth line and the technologically incompatible Scarborough rapid transit. (The Sheppard line suffers from the same problem today.)

- Paris has little branching on the Métro as well, but the Metro only serves inner parts of the metro area, many lines have strong outer anchors (for example, La Défense on Line 1), and two others providing some of the farthest-out service branch. The RER branches much more heavily, as befits a suburban system. Tokyo has little branching on the subway proper, but the subway is for the most part inner-urban, and lines continue to the suburbs along commuter lines, which do branch.

- In North America, this configuration has been common across a variety of new-build systems, especially ones that should have been S-Bahns. BART does this the most extensively, but the Washington Metro is also highly branched for its size, MARTA branches, the light rail systems branch once more than one line is built, and so on. BART in particular imitated the service planning aspect of commuter rail perfectly, and is an S-Bahn in all but the cost of extending the system further.

- I think the main issue in urban or inner-suburban cases is that with typical rapid transit frequencies (3-minute peak service or slightly better, a peak-to-base ratio of 2:1 or somewhat less) the trunk has about 5-minute off-peak service, and if it splits into two branches, this means 10-minute service on the branches. If the branching occurs early enough that dense neighborhoods with short-distance travel demand are on branches, it may be too little. In addition, if one branch has much more demand than the other, then it’s usually hard to match frequency on each branch to demand, since it requires trains to be unevenly spaced.

- The issue is that branch frequency, 10-15 minutes, is in the transition zone between urban show-up-and-go frequency, where schedules do not matter, and suburban frequency, where they do. It’s perhaps less relevant in small cities with small enough transit systems that even 10-minute service is considered very good, but in large cities, people expect more, creating somewhat of an inner-urban metro envy effect. That said, 10-minute suburban and outer-urban service can be done clockface, making the average wait much smaller. It is done on the RER A in the midday off-peak, with three 10-minute branches, and could be done with two 10-minute branches quite easily.

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[diminutive]

This was a good blogpost; I'm surprised by how little attention branching gets in Toronto.

If we ever built a DRL from Eglinton to Dundas West the lines could then branch out into the Western and Eastern suburbs. From Dundas West it would be easy to imagine a branch going along the Georgetown corridor, past the airport and into Brampton, while another branch could go along to Streetsville.

It's almost a perfect line for branching in that (I think) it would meet the criteria of branching after passing through the densest areas, as well as terminating in places (Dundas W, Eglinton) which would allow cost effective expansion into the suburbs (along the rail corridors in the west, hydro corridors in the East)

 

[gweed123]

Since branching is a service planning decision independent of technology, any technology could branch. The branching-friendliest technology is subway-surface

I would disagree. I think the easiest technology to branch would be BRT, because it doesn't involve any switches or anything, just 1 roadway meeting another.

 

[Woodbridge_Heights]

Short turns are a "type" of branching. Except that there is no other branch just the main core and outer segments. Provided the short turns are treated as separate lines and not as operational things.

 

[rbt]

I would disagree. I think the easiest technology to branch would be BRT, because it doesn't involve any switches or anything.

Steering wheel and associated turning components are inside the vehicle. For trains, it's external to the vehicle.

Your still right but there is a something for it.

 

[drum118]

I made that recommendation at TTC last meeting for the DRL.

I can see a branch line for the Eglinton Line going to Sq One as well in the east end. Even the SRT conversion can have branch lines.

When I was in the process of doing a report for TTC back in 2005 on using the Georgetown rail corridor before the ARL surface, I saw a number of branches for this line. Never finished the report once the ARL surface.

Short turning is not a branch line service.

If the Sheppard subway was converted to LRT and ran the full length of Sheppard, you could put in branch lines on it.

There is nothing stopping the BD line having branch lines other than money from the current terminal. If the BD Cloverdale station got built, the branch lines can take place there.

You have to make sure to build the branch line connect correctly, otherwise you will have problems doing it as well delaying service.

BRT is the cheapest and the fastest branching system, but at what cost for the whole system??

 

[gweed123]

Steering wheel and associated turning components are inside the vehicle. For trains, it's external to the vehicle.

Your still right but there is a something for it.

That's true, but with BRT those components exist regardless of whether or not the service is branched. It's called just being a bus .

I made that recommendation at TTC last meeting for the DRL.

I can see a branch line for the Eglinton Line going to Sq One as well in the east end. Even the SRT conversion can have branch lines.

I can definitely see that too. One branch to Pearson, the other to Square One, and then interlining with the Hurontario LRT down to Cooksville (likely the busiest stretch of the Hurontario LRT, and thus a bump in service could be beneficial).

With Eglinton, I can also see the Jane and Don Mills LRTs being branches off the Eglinton line, heading north.

When I was in the process of doing a report for TTC back in 2005 on using the Georgetown rail corridor before the ARL surface, I saw a number of branches for this line. Never finished the report once the ARL surface.

A Woodbridge spur is the one that comes to mind immediately. I'm sure there are a couple others though for serving more areas of Brampton and northern Mississauga.

There is nothing stopping the BD line having branch lines other than money from the current terminal. If the BD Cloverdale station got built, the branch lines can take place there.

Stub to Sherway, main line extends into Mississauga. Or in the east end, branch goes up to STC, another continues along Eglinton to Kingston Rd. Of course that's all purely hypothetical, and isn't likely to happen even in the medium-term.

BRT is the cheapest and the fastest branching system, but at what cost for the whole system??

Depends on ridership numbers. If the trunk of the system (multiple overlapping branches) can handle the ridership, and the individual branches are not yet in the range where LRT is economical, then BRT is definitely the way to go. You can either be subsidizing LRT to low-density suburbs where the ridership doesn't really exist to justify it, or you can accept the added operational costs of operating the trunk section using BRT with very high frequencies.

Unless you have a situation where the suburban areas have sufficient ridership to justify LRT, then you need to make a choice as to where you want to make the subsidy. Of course, you could also move to the hybrid model like Ottawa is doing: LRT for the trunk, with terminus stations where the branches split from each other, and where LRT is no longer economically justifiable (for the time being), and where BRT continues out from those stations.

 

[M II A II R II K]

A B/D split at the west where one goes to Pearson, and the other goes to MCC. And of course branching provides extra coverage.

 

[gweed123]

A B/D split at the west where one goes to Pearson, and the other goes to MCC. And of course branching provides extra coverage.

Personally I don't really see the benefit in sending B-D to Pearson. I mean, Eglinton is already almost there, and it's not like B-D goes downtown. Downtown-bound passengers would still need at least 1 transfer. There are many higher transit priorities than building a N-S subway through the low density suburbia between Bloor and Eglinton along a road like Kipling.

I think the only connections needed to Pearson are Eglinton, a branch of the Mississauga Transitway, and the local branch of the Brampton-Markham GO REX (aka an upgraded version of the ARL so that it's actually useful beyond just an airport shuttle).

If there is going to be any branch, I'd like to see one go to Cloverdale and then continue along Dundas, and then 1 go to the far east side of Sherway, and then continue down Brown's Line to Long Branch. A lot of that area is warehouse retail, which could be a prime target for densification along that route. Not to mention that with the WWLRT and Lakeshore GO REX, Long Branch would be a pretty sizeable transit hub.

 

[M II A II R II K]

There could be a separate RT from Long Branch to the Airport and beyond to service that corridor and scoop up many Mississauga bus routes as well.

On the east side their could be a Main Street split where one branch continues along Danforth and have it continue to Old Scarborough.

 

[gweed123]

There could be a separate RT from Long Branch to the Airport and beyond to service that corridor and scoop up many Mississauga bus routes as well.

On the east side their could be a Main Street split where one branch continues along Danforth and have it continue to Old Scarborough.

I've often thought a Brown's Line/West Mall BRT would do very well in that regard. There isn't really a clear ROW for something like an ICTS line, so it would need to either go on-street, above it, or under it.

A Main St branch is an interesting idea too.

One that I've also been toying with is this: Assume the University-Spadina and Yonge lines are split, with the DRL attached to the Spadina line (see DRTES thread). One of the branching options is to have the DRL split at the West Donlands, with one branch going up towards the Danforth, and one going into the Portlands (for yard purposes, as well as to serve the new community). On the Spadina segment, the Sheppard Subway would be attached to the Spadina Subway just north of Wilson. One branch of the Spadina subway would continue north to Vaughan, and the other would continue east along Sheppard.

This would prevent the dumping of Sheppard passengers onto Yonge, as well as make the Sheppard Subway actually useful, because people could ride it all the way into downtown.

 

[diminutive]

One that I've also been toying with is this: Assume the University-Spadina and Yonge lines are split, with the DRL attached to the Spadina line (see DRTES thread). One of the branching options is to have the DRL split at the West Donlands, with one branch going up towards the Danforth, and one going into the Portlands (for yard purposes, as well as to serve the new community).

Though, by splitting service between Pape and Union you would limit capacity on what would probably be the busiest section (Pape->downtown). It would only work if you ran far more trains towards Pape than to the Portlands. Assuming like 32 trains per hour, even running 10 trains per hour to the Portlands would dilute service to Pape pretty heavily.

Branching would only work if both branche have roughly equal demand levels. Otherwise it would probably be better to run one branch as a spur.

 

[ssiguy2]

Vancouver is an example of where branching works incredibly well.

If the would ditch the Airlink as a limousine route and make it part of the transit system I think an excellent line would be to have both trains running up to roughly Etibiko North and then one heading to Pearson and the other heading north up to Woodbine and Humber College/Hospital. It would also relieve Finch bus traffic greatly and they could pay for it by scrapping the Finch LRt and giving the residents true rapid transit by running EMUs.

 

[gweed123]

Though, by splitting service between Pape and Union you would limit capacity on what would probably be the busiest section (Pape->downtown). It would only work if you ran far more trains towards Pape than to the Portlands. Assuming like 32 trains per hour, even running 10 trains per hour to the Portlands would dilute service to Pape pretty heavily.

Branching would only work if both branche have roughly equal demand levels. Otherwise it would probably be better to run one branch as a spur.

That's a good point. Branching works best once the busiest transfer point on the line has been passed (in this case, Danforth).

I suppose one operational option would be to run both the Vaughan and Sheppard branches to Eglinton & Don Mills, and have the Portlands branch run it's own short-turned route from the Portlands to Eglinton West (or somewhere in that area). That way the Portlands branch is a supplementary service into downtown, and the frequency doesn't severely impact the effectiveness of the main routes. Although even then you end up with a frequency crunch, because you'd probably need 4 min service on both the Sheppard and Vaughan branches, which means combined 2 min frequencies, or 30 trains per hour. You could maybe squeeze in 8 Portlands trains, but that's about it. That's 1 train every ~1:40. If you push Sheppard and Vaughan to 5 min frequencies, it could work, but I don't know if that's enough to handle the demand.

 

[BurlOak]

Practically, branches should be preferably 2 branches, and possibly 3. As the number of branches increase, the service frequency on the branch becomes too small. One thing that has not been mentioned regarding branches is that they should be less costly than the trunk line.

As such, I do not see much oportunity use branching for subways. Having B-D branching in the East up McCowan and along Eglinton requires 2 new lines to be built - with each only running at half the frequency. This is too expensive of a proposition. The only subway branch that make sense is the Sheppard line from Spadina. As gweed123 mentioned, train coming north on Spadina would alternate going east on Sheppard and further north to Vaughan. The reason this one would work is that you really only need to pay for a 4 km line (Downsview to Yonge) and you get a further 5 km thrown in for free (a 9 km long branch all the way to Don Mills).

On Eglinton, we have a huge investment in a tunnel through the central portion. Not building on this investment is really a poor way of planning. One option here in the East is to have one go east (in-median) along Eglinton and one north (in-median) along Don Mills. In the West, one could be Jane and the other Eglinton West. I have seen this proposal here a number of times. I do kind of worry that will just encourage more riders to go to Yonge. Also, half frequency service may not be enough on these major north-south routes - in which case they may need to be grade-separated as well.

Another option in the West would be for one branch to be on Eglinton to Commerce Blvd. on the edge of"Mississauga. The other would go up Weston to Dixon and across to YYZ. Both of these could be in-median. This requires that some type of Mississauga bus service YYZ from the Commerce Blvd. station. In the east, this branching would be harder. They could branch at Kennedy, but I imagine more service would be required on the SRT branch than on the branch that continues on Eglinton. This would also require a grade-separated to Kennedy where the branches split. Maybe another option would be to branch at Don Mills - one continuing all the way on Elglinton and the other maybe going up Don Mills and then across on Lawrence and then up the SRT corridor. Here both Eglinton and Lawrence would be in-median, but the Don Mills leg would have to be grade-separated when the Don Mills LRT is added in.

When all is considered, it almost seems the most cost effective to just build Eglinton fully grade-separated its entire length, rather than doing some branching and paying the cost per km along two routes.