This post will be a lot shorter than the previous one, but it’s a necessary technical prelude to what will follow.
We hear a lot about the relative capacity of various transit modes, and the appropriateness of any mode depends both on its capacity and on the constraints of the alignment where it will operate.
I will start off with a familiar TTC chart (in the format presented at tonight’s public meeting) showing both the theoretical capacity ranges of various modes, and the projected demand on the extended SRT.
What Can LRT Reasonably Carry?
If we believe this table, streetcar/LRT can handle on the order of 13,000 riders, and bus/BRT can handle around 6,000 passengers at peak. These figures need to be carefully examined.
The design capacity of a 30m LRV (the size planned for Transit City routes) is on the order of 150-175 passengers depending on the internal layout. In order to carry 13,000 riders at a peak point, somewhere around 80 cars/hour must pass the peak point. This is impractical with single cars, and two car trains must be used. Even then, this is 40 trains/hour or a headway of 90 seconds.
Also, if that peak load has a major transfer point, there will be an extremely high volume of pedestrian activity comparable to what once existed between the Bloor-Danforth streetcars and the Yonge Subway where a dedicated transfer station was needed.
In practice, I believe that any headway below 2 minutes is impractical for on-street operation given constraints at traffic signals, and the TTC is already of the opinion that even wider minimums such as 4 minutes are preferable.
It is impossible to provide a 4-minute headway carrying 13,000 passengers an hour with LRT trains of a reasonable length on the surface. Conversely, if the line is in a tunnel or on a completely segregated right-of-way, then more frequent operation is quite reasonable, and 13,000 or more could easily be handled with two or three car trains. This leads to the option of branches and short-turn services so that high frequencies are concentrated in areas where there is no interference from road traffic.
If we consider the design criterion for surface operation with signalled intersections to be a 4 minute headway, then 15 two-car trains/hour at 175 passengers/car gives a capacity of just over 5,000. Reducing the headway to 3 minutes gets us up to 7,500.
What Can BRT Reasonably Carry?
For buses, the design capacity of a 40-foot bus is 50-55 passengers (depending on the model), and we can extrapolate this to 75-80 for a 60-foot articulated vehicle. Lower capacities would apply to highway coaches such as used on longer GO routes, but we are only talking about “city” BRT operations here.
A capacity of 6,000 per hour (the top end of the stated BRT capacity) would require over 100 40-foot buses/hour or at least 75 60-foot buses. These headways are below 60 seconds, something that is not feasible for a centre median operation such as proposed for Transit City routes.
Yes, buses operate today on close to one-minute headways, but they do so by passing each other at stops and running a mixture of local and express services. Such operations require passing lanes at stops and this would contribute substantially to the right-of-way requirements. Also, frequent service with comparatively small vehicles produces major capacity and congestion problems at terminals. This can be seen today at Finch Station.
In any event, if we assume a 2 minute headway of 60-foot buses, this gives a capacity of about 2,400 per hour. Higher capacities can be reached with lower headways, but the impact on other road traffic will be severe if any attempt is made to give the buses priority and hence reduce capacity for the rest of the road’s users.
The same constraints of traffic signal interference apply to buses as to LRVs, and if we are going to constrain light rail capacity to at best a 3-minute headway, then a similar approach must be taken for bus alternatives. Conversely, if we are going to talk about sub-minute bus frequencies, then we must be prepared to entertain more frequent LRT operations in medians.
On the Transit City routes, the lowest projected peak demand is on Waterfront West (2,200) with the remainder ranging from 2,700 (Jane and Sheppard East) up to 4,700 (Eglinton). Almost all of the Transit City routes are projected to have demands above the capability of buses running in a centre median. These are 2021 projections from the TTC in November 2007.
Much higher capacities have been claimed for BRT, but these are for lines with large dedicated rights-of-way, passing lanes and generous stations. These are much more akin to dedicated arterial roads than the kind of BRT we could implement for Transit City. Such operation is conceivable in the Finch hydro corridor, but that’s only one line of many, and it would address a very different demand pattern than the Transit City network.
LRT Is The Best Fit
As for the SRT technology, none of the Transit City lines, not even the proposed SRT extension, have projected demands anywhere near the 8,000/hour cutoff point where RT is excessively expensive relative to ridership.
Subways are right off of the map for all Transit City lines including Eglinton.
As I have argued before, the capacity needed for the proposed lines fits well with the capabilities of LRT and particularly with its ability to operate in a variety of configurations. It can operate off-street on dedicated right-of-way, including underground, where needed, but can otherwise stay in a street environment at moderate cost.
The challenge will be to operate the surface routes with as much reliability and comfort as possible.
Steve Munro 
The SRT extension is a colossal waste of money. The cost for the extension and modifications to handle the new cars is 1.2 BILLION dollars, which is not that much less than the cost of a subway. Most of this is for the extension. It is outrageous that the TTC is trying to hide the underwhelming demand on the extension by quoting the demand on the Kennedy-STC section of the line. The cost of the ~4km SRT extension could fund one entire Transit City line, for example a line on Toronto’s busiest bus route, Finch East. It which would serve far more passengers and provide far more benefit than this useless, politically motivated white elephant which doesn’t even work properly in the winter. I was surprised to hear that building the SRT extension as LRT had not already been officially finalized, but I am almost certain that it has been finalized in every other way.
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The SRT was a huge mistake. Each SRT car is apx the same size as a bus. They are about a foot longer, and 4 inches narrower, but otherwise, they are just a bus. 4 buses tied togethor should therefore, logically, be able to provide the same service level. Each SRT car is 41 feet long, meaning two of them are 82 feet long. The TTC is debating purchasing 90 feet long LRV’s for Transit City. Logically, two of these hooked togethor should be able to provide the same capacity as the SRT.
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I wonder what the capacity of SRT (Swan Rapid Transit) technology will be on the chart…it wouldn’t be the first time the TTC considered something on water.
Steve: A commercial swan boat can hold about 20 people. This translates to 100 swans/hour to provide a capacity of 2,000. With appropriate training, we can get the swans to swim close to each other although sufficient canal width for a V formation may be required. Casual observations over the Don Valley from my apartment suggest that flocks of five should be easy to arrange without taking up too much space. This gives a capacity of 100 per flock, and a headway of 3 minutes to achieve 2,000/hour.
Priority signalling will be required to ensure that drawbridges are raised in time for the swans to cross major streets unimpeded.
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Steve,
Swan Boat Capacity is one thing but don’t forget about the need for yards (harbours?) in different parts of the city so the SBV (Swan Boat Vehicles) can roost (sorry) and relax.
And what about the long-distance routes…to Rochester, Hamilton/ Burlington, and even Niagara Falls? Are there larger capacity SBVs available or will we have to have many SBVs traveling at really short headways?
Cheers, m
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I just wanted to clarify with you, the TTC uses the number 10,000 pphpd as the minimum threshold for grade-separated systems to be considered. Does this number come from the capacity of surface LRT?
Also, if one assumes three-vehicle trains (each vehicle carrying 132 passengers) at a minimum headway of 3 minutes, that’s a peak capacity of only 7,920 pphpd. Yes, more passengers can be squeezed in beyond service loads under more extreme circumstances, or tighter headways can be considered, but why doesn’t the TTC use the 7,920 pphpd to justify subways?
Steve: 132 passengers per vehicle is the design load for service planning purposes to ensure that there is actually free space to handle surges and variations over the peak period. If anything, this is low considering that the new LRVs are twice the length of a CLRV which has a service planning load of 74. The CLRVs tend not to pack well because all-door loading is not used at all times and locations, and the stairwells eat up space that might otherwise be occupied by standees. Using a figure of 150 per car would get us up to 9,000 pphpd, and this would still only be five passengers per linear metre of car.
If you had a sustained load of 10k, there would be peaks within the hour where you easily would hit about 13k. Similarly the peak two or three hour period tends to be concentrated within the peak hour, not equally averaged over the longer time. Even our jam-packed Yonge subway has a super-peak lasting at most an hour within the longer peak period.
That three-minute headway is a design constraint imposed so that the LRT doesn’t get in the way of other traffic too much. A closer headway is certainly possible and could be provided by a “wave” of trippers in the peak direction corresponding with peak hour, and given the likelihood of some degree of bunching, two minute headways will occur under normal circumstances fairly often anyhow. Whether the traffic signals will let service through on this sort of headway is another question.
Finally, to answer your question, given the cost of building and operating a subway, the criterion really should be how soon it is actually needed. If the demand estimate today is 10k and growth is almost inevitable, then grade separation will be required. If demand is 3k and growth even to, say, 8k will take many decades, if ever, then “pre building” a subway (or some other grade separated system) is a dubious investment.
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