Thread by @GarethDennis

In March, @CambsPboroCA and @GreaterCambs announced the next stage of their plans for the Cambridgeshire Autonomous Metro (CAM), a bus rapid transit system on steroids that promises to transform transportation in the region 🚌

This spate of press releases followed the publication of the latest report on mass transit for Cambridge… @Steer_Group’s “Strategic Outline Business Case” for the CAM proposal.

Time for a #TestingTransport thread.

First, it is worth understanding why this system was chosen.

The options appraisal process that selected CAM (apparently a @Steer_Group proposal in the first place) was also undertaken by… erm… @Steer_Group back in January 2018.

CAM was selected over light rapid transit because:

1⃣ CAM offers the same benefits as LRT
2⃣ CAM can be delivered for 1/3 of the overall cost of LRT

If either – or both – of these hypotheses can be shown to be false, then the case for this novel system falls away.

Thankfully, @Steer_Group have done my work for me on 2⃣.

In their options appraisal, the capex for the completed CAM system was £1.7bn. In the business case report the capex has climbed to £4.5bn, which is as much as the LRT regional network 💰

1⃣ is the interesting point from my perspective, though, and to interrogate the claim I’ll need to dig a little into the 2019 @Steer_Group report…

The document is long on pages (175 of them) and short on original content…

There's not one mention of the technical challenges associated with bus rapid transit, which is surprising considering that they completely define the economics of the thing.

Anyway, I'm going to skip through and focus on Chapter 3, which defines a baseline technical specification for CAM.

There’s a bit of waffle about the economics, including this caveat about the scope of the assessment which (in my eyes at least) is a great example of why many business case appraisals aren't worth the paper they are printed on:

In any case, the core/inner network is shown in this map (thick lines).

The service provision is for 12 services per hour in each direction on the branches thus 36 services per hour in each direction through the “core” city centre section.

That's incredibly intensive (LRT frequencies don't exceed 16tph in the UK, and only the @Centralline can manage 36tph), but let’s look at what this actually means in practice…

To make comparisons between CAM and an LRT system, we have to assume the vehicles they’d use.

For CAM, I’ll use the Irizar ie tram (specs here: irizar.com/en/autobuses-y…) which is the same vehicle that @Steer_Group favour in their report.

It’s basically an expensive bus.

For our LRT vehicle, I am going to use the vehicle used by @EdinburghTrams: the CAF Urbos 3.

It follows a fairly common design and is easily capable of dealing with narrow/steep streets.

Let’s compare the important characteristics of each of them.

The real tram vehicle (that doesn’t have to lunk its own power supply around) is 50% lighter on its axles than the bus, yet has a 60% higher passenger capacity.

These vehicles give us a maximum system capacity for the core and branch sections of the proposed network.

On the core section, CAM gives a capacity of 5580p/h/d.

An LRT system with the same service pattern would give 9000p/h/d, but that alone isn’t a reason to dismiss the CAM.

If we are going to assess the value of using “trackless” (i.e. tarmac only) bus-trams, we need to consider the annual tonnages that the infrastructure would have to sustain to deliver the service specification.

We measure this in equivalent million gross tonnes per annum (EMGTPA), and the CAM figures are as follows:

core: 4.8EMGTPA
branches: 1.6EMGTPA

For comparison, the peak annual tonnages for HS2 will be around 60EMGTPA.

Edinburgh’s LRT system has an annual tonnage of just under 2EMGTPA, and other systems have figures up to 4EMGTPA.

To put it another way, if annual tonnages are at 2EMGTPA or above, then the whole life cost analysis generally favours steel wheels on steel rails.

Steel wheels on steel rails also give significant energy efficiency benefits, as does the increased passenger capacity and reduced complexity (thus maintenance requirement) of LRT vehicles.

Even a conservative estimate shows an operational emissions advantage of one third 💨

As we’ve seen, LRT vehicles are much lighter than their bus-tram equivalents.

Externally-powered LRT vehicles are also less complex and therefore cheaper to maintain than an internally-powered (by battery or otherwise) bus-tram.

(The report contradicts me here, but doesn’t give any evidence to justify its rather optimistic bus-tram running costs.)

Given all this, I don’t see how it can be said that CAM offers “the same benefits” as LRT, thus 1⃣ doesn't hold up.

Unless I've got the wrong end of the stick completely, it appears that the selection of the CAM option is therefore pretty shaky.

Disagree? Let me know why!

There’s a wider question at play here, and that is the need for Cambridgeshire to receive funding to the tune of £5bn before other urban areas in the UK that are long overdue their own mass transit systems.

There are around 70 major built up areas in the UK (those with combined populations over 100k), and Cambridge ranks around 50th…

Clearly there is more to consider than population size, but 30 places larger than Cambridgeshire have no mass transit system at all.

This includes built-up areas like South Hampshire, Leicester, Brighton/Hove, Bournemouth, Teesside, Stoke-on-Trent, Coventry, Reading, Hull, Preston, Swansea, Derby, Plymouth, Aberdeen, Milton Keynes, Northampton, Norwich, Swindon, Ipswich, Wigan, Mansfield, Oxford and Dundee.

If you ignore low-density commuter rail, then that list includes West Yorkshire (Leeds/Bradford/etc.), Bristol, Belfast and Cardiff/Newport.

I don't think it is reasonable to argue that Cambridge should have a dedicated mass transit system before those cities do.

Much as I love major public transport projects, it takes time and skilled people to deliver them and we have a limited supply of both.

The priority for new mass transit systems should go to those underserved urban areas that are larger or where other investment is shortcoming.

CAM's eye-watering tunnelling costs seem to be palatable because CAM doesn't interrupt the flow of road traffic through Cambridge city centre.

The unit cost of €92m/km is far greater than that of @Crossrail, which is mad if you consider the specification of the two systems.

That doesn't compare favourably with the (admittedly expensive) first phase of @EdinburghTrams (€32m/km), or the very complex @MCRMetrolink 2CC project through Manchester’s city centre (€74m/km), or High Speed 2 (€47m/km) which will include several massive hub stations.

Even if Cambridgeshire can justify its own mass transit system, excluding cars from the city streets and enabling a free-flowing LRT system would be much quicker to build AND more cost-effective.

In the meantime, a far better approach would be to remove city centre parking, increase charges for on-street parking and invest heavily in segregated cycling infrastructure.

People seem to forget that cars ARE congestion – remove cars and you remove congestion.

Now, it's always good to end with a joke, and in my eyes there's no better joke in all of this than the name of the system:

The Cambridgeshire AUTONOMOUS Metro.

Given that the system's autonomy is only mentioned in passing a few times in the report, and only ever as a distant possibility, calling it an "autonomous" metro is pretty hilarious (and drastically misleading).

They also talk a bit about platooning (again, unproven) as a means to expand capacity… They suggest that three of the units "coupled" together, essentially giving a (rather insane) 108 service per hour timetable.

Why not run a less intensive service with larger units?

That sort of strange thinking seems to be typical of these proposals. To summarise, the Cambridgeshire Autonomous Metro:

❌ costs the same as LRT 💰
❌ offers fewer benefits 📊
❌ isn't actually autonomous 🤖

So that'll have to be a whopping great thumbs down from me 👎

If you've enjoyed this #TestingTransport thread, then feel free to donate me a coffee at ko-fi.com/garethdennis… This stuff gets done when I should be sleeping, so every little drop* helps keep me awake and creating more!

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