I have read a bunch of pieces from Cato institute, among others, that I find a little frustrating. Yes, if you run enough buses you can exceed the capacity of a single rail each way – LRT – that you constrain to 3 cars, and 20 trains per hour. However, when you make that comparison, what are in effect doing? Yes, you can have buses passing each other and staggered stops, but that either means an open right of way, and being subjected to congestion, or well having platforms plus a stop lane plus a running lane for the bus in each direction. This means 3 lanes dedicated to buses assuming the stop directions are offset. If you are running say a 3 car LRT at 3 minutes, you have a very comfortable capacity of 8100, and a reasonably one of 9,000. If you are going to match this, and are looking at replacing this capacity with articulated buses you are looking at something on the order of 120 buses per hour. Why are we limiting the LRT to 20 trains per hour? This is based entirely on signal timing and pedestrian flows. If you are looking at a reasonable 3 minute signal cycle (that is so that you can actually time them, as opposed to having a light you are trying to catch on every cycle of 1 or so minutes) and buses running at 120 per hour, well if the buses are perfectly coordinated, there are 4 buses passing through each green signal, perhaps more to the point 90 seconds with no buses, followed by 90 seconds with 4, 2 of which – assuming everything is working perfectly – are right on top of each other. If you are going to assume that you do not need timed signals for the right of way, why limit LRT to 20 trains per hour?
The other question that we all need to discuss is – why are we limiting the LRT to 3 cars? It is important to remind ourselves, that the core reason is pedestrian flows, and this is determined by the number of people alighting at any given stop, during a signal cycle. This is not affected by the vehicle type but rather by the timing of capacity arriving at the stop, 120 vehicles or 20 it will still be the same number of passengers, trying to cross during a limited signal.
So yes, if you offset stops, organize for platoons of vehicles, are willing to dedicate a lane equivalent for stops and one in each direction for travel, platforms on – you can achieve the same or even greater capacity, however, you will need much more space in the roadway – which is the primary argument against LRT, and you will still have pedestrian flow issues, which is what will limit the capacity of LRT. If you build stations with walkways etc, and are in an area where you are prepared to ensure there are only crossing streets at a spacing of greater than 120 meters, you could run trains of 4 cars – and a capacity of 12,000. Increase the road spacing to 150 meters you can easily get 15,000 – and I would be surprised if achieving this road spacing is really an issue. However, think of 750 passengers passing through a point in each direction in 3 minutes, and half of them want to alight at a given stop. So you have 750 pedestrians trying to cross at a given intersection – in a given signal timing. This is not really a question of the capacity of the mode, but rather station planning.
So we need to ask the questions with regards to what makes sense, and one of the question needs to be – how much space are we able to dedicate to transit within the road, can we actually have 3 lanes and 2 sets of platforms, or are we going to restrict it to 2 and 1 set of platforms. Next what kind of stations are we building, if we are going to build stations to handle large pedestrian flows, then we can increase the capacity of LRT or BRT, but lets be straight forward about it. We also need to ask the questions about impact on the corridor, would you want to back onto a corridor with 120 Articulated buses roar by every hour (or 180 regular buses)? If we dedicate the space, design the stations, and ensure that road crossings are sparse – we could run 5, or even 6 car LRTs, but there really is not many spaces where there would be near that level of demand, and where there is, we would likely want to, be able to justify, a subway, with stations designed to handle the flows of riders.
BRT in the GTA, has it role, and does even within Toronto, but the space in the rights of way, flows, timing, and destinations of riders are key in making the choices. LRT makes more sense in a 36 meter right of way with more than 2800 riders in peak hour & direction. That would mean 2 fully loaded articulated buses per signal in a single direction.