So, after circling in my head for about seven years it’s finally time to let this pigeon fly.
Before we begin, I just want highlight that this is a two-part post: Today I highlight some inconvenient truths about light rail before tomorrow responding to comments.
Tomorrow’s post will also discuss some new transport technologies that I would like to see carry Auckland into the future. By the end of it all I hope to leave you pleasantly surprised, even enthusiastic. I know I am.
But first let’s turn to the dirty task of setting the record straight with respect to light rail. In the following paragraphs I discuss some of the common arguments put forward in support of light rail, before outlining the reasons why I think they (generally) do not hold much weight.
1. Capacity: It is sometimes argued that light rail has a capacity advantage over over bus-based solutions. But several developing cities (e.g. Bogota) have developed bus rapid transit (BRT) solutions that carry 40,000 pax/hour, when light rail struggles to break 20,000 pax/hour. At this point some people change tack and argue achieving this capacity requires horrible BRT “super-highways” (i.e. grade-separated lanes with skip stops). Even if it’s true it’s not relevant to debates about capacity: The evidence quite clearly shows that light rail does not have a capacity advantage over buses. End of discussion.
2. Resilience: Light rail is supposedly more resilient than buses because the former is powered by electricity, rather than diesel. But buses do not have to run on diesel – Wellington’s trolley buses being just one example. Auckland could switch-over to electric trolley buses if warranted by energy prices. The resilience argument becomes even shakier when you consider that energy security is but one of the many potential risks to transport systems. Other unforeseen and calamitous events can, and do, befall cities; events to which light rail systems seem particularly vulnerable. Christchurch’s recent earthquakes are testament to the types of situations that can render light rail systems completely useless, as are more common situations where things simply get in the way. In my mind “resilience” is a smoke-screen that fails to recognise situations where not being restricted by tracks and catenaries is an advantage.
3. Ride quality and negative externalities: Some argue that light rail provides a higher quality ride and generates less negative externalities (such as noise, vibrations, and air pollution) than do bus-based solutions. And if we compare multi-million dollar, spanking new electric light rail vehicles running on highly-engineered tracks to Auckland’s clapped-out old diesel buses that bounce along pot-holed streets – then the answer is definitely “yes”. But this is like observing that a new VW Golf handles better than a 30 year old ride on lawnmower – fresh apples versus rotten oranges. Indeed, there is no (obvious) technical reason why buses could not be as clean, quiet, and smooth to ride as light rail. In fact, my engineering intuition suggests that because buses are lighter and have pneumatic tyres they should be cleaner, quieter, and smoother than light rail. The one aspect of ride quality where light rail may have a real advantage is in terms of their reduced lateral movement – which obviously derives from the fact they run along fixed tracks. But in general, most negative perceptions of buses is more to do with correlation than causation: Since their very inception buses been viewed as a form of transport that is mainly used by low income people. The absence of quality buses in New Zealand says more about our disdain for people who ride buses, than it does about bus technology per se. Many European bus systems, e.g. in France and the Netherlands, do not skimp on quality features like we do.
4. Place-making: I do admit that light rail has an advantage over buses in what is loosely referred to as “place-making.” But let’s unpack this term so we can get closer to the attributes that confer the advantage. And let’s also be clear that it’s not because of light rail’s “look” – it has to be something deeper. In my experience I have found that pedestrians are more relaxed around light rail than they are around buses, as my colleague’s recent experience in Amsterdam attests. But what is the source of pedestrians’ comfort? I suspect that the main reason pedestrians are more relaxed around light rail is because the right-of-way is clearly defined by the tracks in the ground. Basically, because light rail runs along tracks people know where the vehicle will travel and when they need to move out of the way. In contrast, standing in front of buses as they career down the street towards you is not particularly relaxing. So I’d suggest that fixed track transport technologies, such as light rail, have a ‘place-making’ advantage in street environments that support high pedestrian volumes – mainly because people feel safer and more comfortable being close to moving vehicles that have clearly defined trajectories.
Before we wrap up let’s summarise some of light rail’s other disadvantages: Light rail is quite expensive to build (because of the tracks and catenaries) and operate. Try buying a money tree, growing it for 30 years, and then killing it. OK that’s a slight exaggeration: Dublin’s (slick) LUAS line runs at an operating surplus while Göteborg’s (delightful) tram system has a fare recovery of around the 60-70%. But they are the exceptions, not the rule. In most places light rail struggles to hit 50% fare recovery, let alone start to cover its very high capital costs. And light rail also struggles with geometric obstacles: It does not really do well on corners or hills, such as the Auckland Harbor Bridge (which is one of the reasons the Northern Busway was not light rail).
When you gather all this evidence together (as well some other factors that I have not had time to discuss – such as choke point geometry and density) I have to conclude that light rail is not the solution to Auckland’s transport problems. Nonetheless, light rail does have some undoubted advantages in terms of ride quality and place-making, both of which stem from the fact that it runs on fixed tracks.
The question I will leave you with (and which I will explore in tomorrow’s post after responding to comments on today’s post) is whether the small advantages associated with fixed tracks could possibly be transferred to buses?
If you’re itching to know more about tomorrow’s post, then have a look at this and this. Alternatively, if you are more interested in the potential benefits of ICT technologies and car-pooling, then have a look at this.
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Stu, re 1. not end of story. You can’t compare four lanes of one mode [Bogata] to two lanes of another [light rail] and shout that you’ve found a clear winner. Apples with apples please.
I can only agree with Patrick R. If you look at the buses through Wellington’s Golden Mile section, it’s a mess. For a BRT situation to be useful, you must place it in the right set of constraints, such as easily overtaking one another.
Our 40 year-old trains (albeit with newer bogies) have a ride that is vastly superior to the latest Designline buses in the NZ Bus fleet. Unless the new UK buses have vastly superior suspension, and the city council can guarantee that the roads can be maintained to a very high standard, they won’t be able to provide a comparable ride quality to LRT.
Based on the Waterfront tramway costs ($7.5m for 1.5km), a 7.5km Queen St/K Rd/Ponsonby Rd/College Hill loop will cost $37m (plus vehicles). This cost, plus the annual maintenance cost over the 30+ year life, has to be compared to the cost of providing a high quality road over the same time period, to know which would give the best whole-of-life value.
Brisbane’s busway does offer such a standard. Unfortunately, for this reason it’s been incredibly expensive, comparable to heavy rail in price.
As admin has pointed out many times, no single technology will solve all transport issues. It is not a matter of pitting buses against trains against cars against trams and declaring an all-out winner but deciding which offers the best solution for a particular problem. I’d go for the more nuanced conclusion that “light rail is not the solution to some of Auckland’s transport problems but may well solve some admirably”.
The Siemens e-BRT idea is indeed quite interesting. Though with no example projects to speak of, I would remain dubious about their cost claims of being so much less than LRT with tracks and overhead lines. Also, they say they use “supercapacitors” to store the energy between stops. From a quick (admittedly quite brief) look, that technology is also still in development, and has not been widely tested.
In short, any system just using a modern busway/right of way would still be buses (and have all the issues with exhaust (not THAT much these days, admittedly) and even more importantly, fuel cost risks. Any system other than using “plain” buses on an upgraded busway (such as using e-BRT) has issues with introducing yet another type of transport system (i.e. not widely tested and/or extra start-up costs for specialised infrastructure) as LRT would have in Auckland, and so is not necessarily as clearly favoured as Stu seems to consider.
I agree that some of the pro-LRT case is emotional. But that part is also because PEOPLE react positively emotionally to modern LRT (at least that is my perception).
Surely we would rather have light rail – instead of buses – running across Te Wero and through the heart of the new waterfront area?
I agree that light rail is the not the silver bullet, and that buses will be the real driver of PT usage, supported by an expanding (and improving) heavy rail network. Light rail makes no sense in many areas where it is suggested (e.g. to replace the NEX), but its clearly a better option in other areas. The Waterfront/Quay St and Dominion Rd for example.
Like most efforts to make clear “inconvenient truths”, this article is particularly confrontational. Which is unfortunate. Most of these points need addressing in a decent form, and I’ll come back to them later.
If I may add one thing before doing what I’m supposed to do today, it’s that I think “pro-light rail” people in NZ, (those who argue it should be part of the mix), are remarkably clear headed about its advantages and limitations, and live very much within the world that is rather than an idealised one.
Capacity – agree with Patrick, you need to compare apples with apples. A 4+ lane busway takes up far more space than a 2 rack Light Rail. How about comparing potential pax per hour per direction by area of land consumed???
Cost – This is usually a good one to argue about, but it really has more to do with the RoW built rather than the mode. Grade seperated busways through through built up urban areas are fiendishly expensive, jsut like LRT is for the same class of RoW and environment. Laying down tram tracks and putting up caternary poles like at the Tank Farm is cheap bt then you have a low grade RoW and painting bus lanes is cheap also. Light rail vehciles are more expensive to buy about 3 times the price of buses per passenger, but then light rail is also cheaper to operate and maintian than buses. So as you can see cost is a complex issue.
In my opinion light-rail has a limited but important role to play in Auckland’s transport future and I am curious and look forward to Stuart’s next post. Particularly if he looks at the circumstances where light-rail is the best technology and if he think those circumstances exist (or will exist in the future) in Auckland.
The capacity issue is something I would like to see explored further. In particular the cost effectiveness of different technologies at different capacity levels. It may make sense to run a zillion buses in Bogota or Curitiba because wages are low. Does it still make sense in Auckland? One would think that LRT becomes more cost effective as you can shift more people per driver.
I also think in a situation where you have a very constrained corridor, like Dominion Rd, LRT can give you more capacity per metre of width than the BRT highways that Bogota/Curitiba have.
Finally, the pedestrian amenity issue does matter – especially for a corridor like Dominion Rd. We want more people living and working and shopping on that corridor but we also want to shift many more people along it. Finding that balance with any bus based solution is going to be impossible in the long run I think.
I object to discussions where one mode is pitted against another in some sort of almost context-free situation and then asked to decide which is the “best” mode.
The truth is, it depends on the context as well. For example, BRT and LRT were studied in depth for the Gold Coast Light Rail Project and it was found that in the constrained corridor, Light Rail DOES have higher capacity than buses
because you can run it in Class B right of way. To achieve higher capacity using buses, grade separation would be needed, and in that particular context, that would just not be possible.
I suspect that many of the comparisons to “capacity” of mode are a bit suspect. ANY mode can have high capacity, provided it is designed for that. If you put a 40 lane freeway in, you can also achieve 40 000 pphd by using single occupant vehicles.
It says nothing whether that is economical of feasible. Labour costs to drive buses in developing countries may stack up better in those contexts than say perhaps in an Australian or New Zealand context. Not much use trying to achieve 40 000 pphd
on Australian or NZ contexts if the wages / labour costs etc favours rail options.
Brisbanes Cultural Centre busway is at capacity and runs approximately 180 buses per hour, which puts it at 9000 pphd in Class B ROW.
I think the main priorities for Auckland are:
1. Getting the integrated ticketing and network planning by central authority
2. Upping the frequency on key trunk routes by copying the Brisbane BUZ concept- the Beeline is a good start but off peak and weekends need to be broadened
3. The rail system needs to be sorted out and frequencies upped so that it acts more like a metro and less like a commuter rail system
Oh, and just remember!
CAR has the best service characteristics of ALL modes! And don’t talk to me about capacity either- something like 80% of all travel done in cities is by car- so be careful!
If you applied your criteria a bit further and extend it to walking, bicycles and car, you would wrongly conclude that the only legitimate mode to get around in is by car.
Yes, most ‘mode against mode’ debates are fetishism pure and simple. I know, as a rail fan, that I just can’t raise a smile when I look at a bus whereas I can stand for hours looking at trains.
But this fandom does not pass muster as influencing whether I actually favour the mode or not.
Decisions must be made on science and facts.
Buses work up to a certain number of pax per hour per direction, and then rail based solutions kick in.
End of story.
Most Aust and NZ routes struggle to have the number of pax per hour per direction that justify rail, so bus transport should be more widespread than it is.
But some routes do justify rail transport, and bus fanatics can be as bad as rail ones when their case is lost.
Look at the new Mandurah line for example, and tell me buses could or should deliver that level of service.
When people start telling you that employing 100 bus drivers is better than 6 train drivers to carry a given number of people, you should really start looking at:
-systemic overmanning and other inefficiencies in our legacy rail operations (Auckland!!!!!!!!!!_
-ridiculous infrastructure costs, overblown more in rail than road
-errors in payscales and industrial agreements, which cause unjustifiable disparaties.
Stu is quick to complain about comparing buses “as you find them” with light rail “in the ideal” and how this weighs down the case for buses – but neglects to mention how disadvantaged legacy rail operations are in these sorts of comparisons.
I think one of the main conclusions from this thread is that the sentence ‘end of story’ is almost always cover for a narrowing of an argument.
I’m no fan of light rail per se at all, but where I do see it being worth considering in Ak is precisely those routes that do not offer ROW for any mode, like Queen St/Dom Rd, or Tamaki Drive, or Ponsonby/Grey Lynn. So there is no point in talking about the advantages of any mode where the examples are on their own ROW. The only way we can get separate ROW in central AK now is with tunneling or on elevated viaducts. And if we’re going to spend that kind of money the clear advantages of extending the existing heavy rail network is no more expensive than the others ergo, a no brainer. Hence the CRL. [end of story- just kidding]
If cost were no issue we could solve Dominion Rd’s problems with a heavy rail tunnel up the length of it and lovely bike lanes, leafy medians, and local traffic and parking at grade; not going to happen. So what’s the next best thing? It’s a fight really between LRT and bus privilege. The later has lower cost and flexibility and the former has electric propulsion, a bit of glamour [don’t knock it, great marketing], route predictability, and street dominance [drivers won’t mess with trams as much as they do buses]. It’s a debate we need to have, and thanks for Stu for cranking it up again. BUT, as someone said above it does need to be context specific, and the key specific to all of these routes is no separate ROW for the mode. So Bogata and Curitiba are completely irrelevant.
These are all reasonably valid theoretical points and I would conceptually agree in most respects, but the real comparison needs to be made in relation to specific real world constraints and opportunities. (As an aside, If the is one thing worse than mode-fetishism it’s mode-fetishism dressed as anti-fetishism!).
As pointed out already no one realistically suggests that light rail is *the* solution to all of Aucklands transport issues (likewise neither with just buses, trains, ferries etc), but in particular corridors it may be the best option.
Dominion road is a perfect example, a near saturated linear bus service constrained on a narrow arterial in a pair or 3.2m lanes and affected by frequent intersections. Given the historic town centres a Bogota style freeway median busway is out of the question. Even a standard width bus lane is out of the question. Yet light rail would happily fit within the existing corridor, and provide perhaps twice the real world pax capacity than bus systems could achieve under the same constraints.
Another is the waterfront area, yes buses could provide sufficient capacity yet in such a high profile area ‘placemaking’, visibility and the ‘aura’ of the mode is more important than the theoretical capacity.
Of cours it works the other way too. I think the idea of light rail on the northern busway corridor is inferior to buses given the lesser constraints on space, the extra cost of infrastructure and the inability to run express tram services beyond the main corridor.
I’m not going to enter the debate about which technology is better as I think they both have their place but one thing I have noticed is that whenever this debate crops up the people who are arguing against rail based solutions always bring up the worst case scenario i.e. broken rails or a car blocking the way then show a picture of bus operating in a perfect scenario.
The corridor width is a pretty major issue to overlook when talking about transport in a city. The passing tolerance can be measured and any buffer for opposing tram tracks set in stone, even going around corners. Buses on the other hand will crawl when they are given narrow spaces — you need a much wider space for them to move freely.
The defined/invariable width helps in pedestrian friendly spaces too, as they can tell exactly where the limit is. It is also a lot easier for them to cross the corridor, as it is probably only half the width.
Regarding the noise, steel-on-steel is lower friction than rubber on chip-seal, hence the quieter and smoother operation. There is a reason why most ball-bearings are metal-on-metal!
All of the above are important advantages for installing light rail/trams in cities. Buses have important advantages too; the North Shore busway is great. But I’d prefer trams in what should be our most people-friendly areas, such as Queen Street, Dominion Road, Ponsonby Road, etc.
Generally, Bogota BRT is two lane only. Therefore, the same space is consumed as LRT. Regardless, the point is that very high capacity can be achieved by BRT. Not that it has to be! This BRT film by streetfilms which shows you how it works. What is also of note, is how easily the bus line is integrated into low density pedestrian environmenst as shown in the clip.
Now, I think that the authors point of this post is to dismiss some of the common misconceptions regarding the advantages of LRT over BRT. He deals with the points of capacity, resilience and costs in what comes across (unfortunately) in an confrontational manner (that was one caged pigeon). However for me, these points paint a rather clear picture that in terms of Auckland, BRT is the best overall solution for its major routes which do not require heavy rail just yet such as Great North Road, Dominion Rd, Manukau Rd etc.
He does however concede that, trams due to the more fixed route nature are more easily able to fit into pedestrian environment. Therefore, within a dense pedestrian traffic zone such future Queen St or Wellingtons Golden mile, perhaps BRT is not better than LRT?
We may see tomorrow.
At the moment I am finishing off a big academic paper for a transport research conference, comparing LRT and BRT and their costs. The conclusions:
* There are clear situations where BRT is to be preferred and other situations where LRT should be used. Hence, a busway for the northwestern motorway and LRT for Dominion Rd.
* There is a big need to ensure that you are comparing like-with-like – that means distinguishing median-separated schemes (LRT for Dominion Rd) from full grade-separated schemes (Northern Busway, Docklands Light Rail).
* Where LRT and BRT have been compared for the same corridor, LRT is generally given a twenty percent patronage advantage – at four times the cost per mile.
* There is no particular conclusion about operating costs, because while LRT is cheaper to operate for peak loads, at off-peak loads it is expensive to run an LRV when a bus would do the job (for the load) just as well. So these things tend to balance out.
* LRT at the high end can be astronomically expensive (>£100m/mile, $NZ135m/km), but that is because tunnelling is involved.
* Neither mode is spared from cost blowouts – the busway in Cambridgeshire, and Edinburgh LRT, are both going to cost double what they were intended to. Edinburgh’s is tracking towards costing $NZ130m/km.
If anyone is interested in looking further at the work, my work email is ross dot clark /at/ scotland dot gsi dot gov dot uk.
Sounds really interesting Ross. If you want to email me anything that can be shared publicly that would be awesome. I think it is helpful to shed light on this issue and it’s a useful discussion.
Thank you for bring up this topic Stu. You have really opened up eyes to the benefits of buses. No doubt we can improve our existing bus services to allow for faster boarding, pay machines, bus stations, bigger buses, route simplification, integrated ticketing, comfort and accessibility. This will significantly grow our bus services in NZ. But buses will only be suitable in some situations.
We need to decide what type of city we want to create and how we are grow. I would consider LRT and BRT to have the similar capacity levels. BRT however, runs at much faster speeds, uses more land, and is generally grade separated. LRT on the other hand attracts growth and runs down the middle of city streets. Grade separation and at level transport serve much different transport purposes. Bus lanes on the other hand carry much less people than LRT but have very similar characteristics.
Several posts were done around a year ago about transport and the best speeds for increased street level development. I do not believe BRT would be suitable in this case over LRT for highly dense populations. But there are several examples were Bus lanes are just as good due to a lower level population. While on the other hand, BRT will work well when the population is more spread out.
One thing on the ‘like with like’ point, while it is important for a scientifically valid comparison this isn’t always the case in reality. I guess you could say you need to look at ecological validity.
My main point is that you sure can have super geometry bus rights of way, superior stop/station designs and top quality and capacity vehicles, but this usually isn’t the case due to the costs involved. However with a rail based system the track geometry must be smooth and even and the vehicles almost always have better capacity due to the physics of wheel on rail vs tyre on road. What I’m saying is that while bus systems *can* be built to exacting standards, rail systems more or less must be. That means that to chose rail in the real world guarantees a quality transport route but that is not the same with buses. Like Auckland experienced when it shifted the central connector from light rail to bus lane based, the real world outcome is a cheaper and less effective right of way in the name of saving costs.
I would question the point that street busway costs four times less than street tramway, this may be simply because bus measures tend to be built to lesser standards. If we are talking about a super smooth and even roadway with permanently segregated lanes, independent traffic signalling and capacious articulated vehicles (all things that are ‘standard’ on light rail but exceptional on bus routes) I imagine a bus based solution would cost just as much as a tram based one.
Yes, but how much are we actually prepared to pay for the ‘superior’ quality of LRT?
Busways are not built to the same standards as light rail systems unless they really need to be. You get what you pay for, but there’s not much point in providing a BMW-standard solution for a Toyota-standard problem. Saving money is a perfectly valid policy goal, if resources are limited.
Also, BRT and LRT systems only really come together on costs when you are dealing with systems which need a lot of grade-separation, like the North Shore Busway. Feel free to email me directly if you want to see where my work has got to.
We’re so used to the clapped out wreck in Auckland to extend your car metaphor, and it really is time to build something properly if we want it to work. Ak now has the population and the growth to support any of these systems and the thing I would like to see given as much weight as the cost issue is the longevity of the project. It really is time we built proper legacy infrastructure for the sake of the quality of the city and for cost benefit over the entire life of projects. No more short-termism. Sydney built it’s metro during the depression, remember.
The political problem with bus solutions is that they garner support from PT enemies who can then claim to be funding PT by building roads: You know the line: ‘buses use roads too’. We used to hear this from Cullen, who extremely reluctantly spent a little on PT in AK, most through where he was persuaded that motorists would benefit [grade separation at New Lynn, for example], and we hear it now from English, Joyce, Kaye, Michael Barnett, Banks, and nearly everyone out on the right as they fight the case against the CRL, and defend their absurd funding imbalances. So be very careful who you’ll find yourself in bed with when promoting bus solutions.
The answer is of course a mix: Some routes both in terms of capacity and street geography suit LRT, esp. Dom Rd, as mentioned above. And others suit BRT like the Northern Busway and we need another on the NW corridor.
One thing that really needs to be considered here is operational costs, which in our country are considerable due to the cost of labour. Putting aside grade separated routes, the sort of articulated bus that could actually operate on Auckland streets could handle perhaps 80 pax at crush load. An articulated tram can carry 250 or more. (Yes there are some very long bus designs but I can’t see one getting through K Rd and turning around at Britomart!). So perhaps it is worth spending double on the capex to quarter the staffing costs in busy routes in constrained corridors.
Also perhaps it is sometimes better to go with the BMW option if the goal is to boost partronage, especially if you are looking to attract new markets. Some people pooh pooh the idea but I think that buses have a very real image problem (with some markets at least) that trams don’t suffer from.
Light rail certainly isn’t a panacea, but I think there is a small but important niche where it is the best option.
I think one of the key advantages of sticking with a rubber/tarmac combination is that it is more future proof. Communication technology has the potential to deliver better pricing, better sharing, and even driverless vehicles (eliminate or drastically reduce parking). Sinking a huge amount of capital into trains loses those opportunities.
yeah that diesel engine is really future proof
We already have driverless trains. I don’t think they’ll be driver-less buses hurtling down dominion road in my lifetime.
If we are going to even discuss Light Rail then we need to compare the best in that area with the best in BRT and ensure we are equating apples with apples. Dissing LRT because of overhead gear and then offering a BRT solution like Siemens using charging plates is ignoring the same solution could be applied to LRT. At the end of the day there has been more than enough written about the environmental problems emanating from conventional buses so if we ignore them we should compare LRT running on rubber tyres such as Montreal Metro or the Matra system in Lille.
Rubber tyre LRT can cope with much steeper gradients than steel wheel (13%) and provide a smoother rides, faster acceleration and quieter rides both in and outside train. We then have a system that we can compare with the best of BRT but you always come back to capacity that a train can carry compared to a bus. One Driver per train or many drivers for many buses to achieve the same number of people.
Sigh. The issue with Bogota is not that it’s ugly (though it is). It’s that it’s a four-lane grade-separated system with crush loads. If you want to see what two-track mostly-but-not-fully-grade-separated rail can do with crush loads, look at the Chuo Rapid Line: 28 tph at the peak, each with about 3,000 passengers. If you want to see a four-track system, double that amount. And that’s without getting into labor costs… (No, it’s not a wash, not even off-peak, assuming your planners are smarter than the idiots in Dallas, San Jose, and other American underperformers and won’t build anything on marginal corridors.)
Another issue is that regional rail and light rail work differently. Regional trains can quite easily be shortened. In Germany, regional lines can run with just a single car off-peak, but with several cars (and just one driver!) at the peak. The operating cost is similar to that of a bus, but the ridership is twice as high because trains have better performance. Rail comes in many forms – a BMW solution, a Toyota solution, a VW solution, a Renault solution. BRT in that analogy is a Chevrolet.
This debate is getting silly. I’m happy if it is narrowed, or shut down altogether.
I wrote sometime ago how bus versus light rail (or heavy rail for that matter) is just a retelling of the old ‘making soup from a stone’ parable.
The stranger arrives in the village to find no room at the inn, all the shutters up and no-one wants to talk to him. He has nothing to eat but finds a cooking pot, some water and starts a fire. He heats the water, but having nothing else, puts a stone in the water.
The village people peer out from the shutters at him and wonder what he is doing. One emerges to ask him. He says he’s making soup from the stone.
The villager asks how it tastes, and he says OK, just a bit bland and how much better it would be with some carrot. So the villager dashes inside and brings out a carrot.
A second villager emerges and asks the same question, to be told the soup is only missing some potato. And so it goes until the pot is filled with vegies. At which point he removes the stone and has a soup.
You retell the story starting with a clapped out old bus. It works fine, but how much nicer it would be if it had its own right of way. And if the right of way was smooth. And if the vehicle was large and articulated. And electric. And had stations. And off-vehicle fare collection. And a regular timetable. And went really fast. And if the vehicles could be coupled in multiple. And on it goes. You have a bus that isn’t really a bus any more.
And BRT fans start stretching the truth, describing a tram in every other guise.