Affordable Mass Transit for Cambridge1 Paper for the CAM-TAC Committee meeting, 10:30am Thursday 28 May

1. Introduction

The Cambridgeshire and Peterborough Independent Economic Review (CPIER) published its final report on the future economic prospects for the region in late 2018. The report was prepared by the Cambridgeshire and Peterborough Independent Economic Commission (CPIEC) and it pointed to very fast rates of economic and employment growth over the next few decades.

Much of this growth will be concentrated in and around the City of Cambridge. This will put further pressure on an already overstretched transport infrastructure and recognition of this problem has given rise to the current proposals for building the Cambridge Autonomous Metro (CAM).

This note summarises the findings of the CAM Technical Advisory Committee (CAM-TAC), a body which was established by the Mayor in May 2019 with a brief to review and critique progress to date.

2. Cambridge Autonomous Metro

City authorities are increasingly looking to conventional mass transit systems to address their congestion problems and Cambridge is no exception. Light Rail/Tram (LRT) systems are well suited to dealing with the heavy ‘tidal flow’ demands of commuter traffic which lie at the root of Cambridge’s transport problems.

Since the early 1980’s, LRT’s have become very popular in the UK. But these systems are costly. The key metric (cost per passenger kilometre) is very high unless the passenger transfer rates are also very high. In broad terms, around 5,000 passengers per hour per direction (pphpd) are required to make a reasonable economic case for installing an LRT system. This means that LRT’s are far beyond the reach of small cities with populations in the range 100,000 – 400,000 because passenger demand levels in these cities usually lie in the order of only 2,000 – 3,000 pphpd. Cambridge lies at the smaller end of this spectrum, so the cost disadvantages are acute.

As currently proposed, CAM seeks to capture the advantages of LRT whilst avoiding the high costs by adopting new, automotive-based, technologies. The preferred solution proposes the use of tram-like vehicles which run under autonomous control on rubber tyres on a normal road surface (no rails). The network topology is shown In the diagram below. The network includes 12km of two-way tunnels and two underground stations at key locations within the Central Core zone which is shown in grey.

1 This paper was written by Dr David Cleevely and Professor John Miles of the CAM-TAC committee. They were assisted by Xiaofan Zhang, a fourth year Engineering student at Selwyn College, University of Cambridge. His Master's project explores the role of autonomous mobility in Cambridge and is supervised by Professor John Miles. He has provided invaluable input to the design of vehicles and stations. Before working on his Master's project he was the Programme Director of Cambridge University Eco Racing, where he led the development of Helia, one of the world's most efficient electric family cars.

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Whilst the autonomous, road-going characteristics of the vehicle are novel, the concept of operations for the system, and the nature of the service provided to travellers, will reflect that of a conventional LRT in almost all respects. This gives CAM-TAC several concerns.

• The tram-like size of the proposed vehicle leads to the scale of the fixed infrastructure being unnecessarily large. Constructing the fixed infrastructure represents the dominant part of the total system capital cost, and cost is related to size. Unnecessarily large dimensions are highly unwelcome. In our view, the system as proposed is likely to be unaffordable. (This comment applies particularly to the tunnels and sub-surface stations in the Central Core zone).

• Autonomous vehicle technologies, fleet operations management systems, and passenger journey planning Apps are all developing at great pace. In our view, the system as proposed is too inflexible with regard to future vehicle evolution. (Again, this comment applies particularly to the tunnels and sub-surface stations in the Central Core zone).

For these two reasons, CAM-TAC recommends that an alternative approach be explored before binding decisions are made.

3. An Alternative Approach

Our transport problems arise because the private car has become ubiquitous. It offers an unparalleled combination of personal convenience, flexibility, and affordability. Providing a public transport alternative which is more attractive than taking the car is a very difficult challenge. If this challenge is to be met successfully, the proposed solution must be convenient to use, flexible, and affordable. More than this, it must be sufficiently attractive to tempt travellers out of their cars when the system is first unveiled, and it must remain attractive over the decades which are to come.

The fixed infrastructure solution for Cambridge must anticipate the future. Simplistically, it must address:

• The present timeframe – where the current, and imminent, state of the art is well defined and can be proposed with a high degree of confidence. This must deliver fast, frequent, reliable services that trump the inconveniences of the commuter car journey (slow, unpredictable peak-hour journey times, with parking problems on arrival at the destination).

• The future timeframe – where the prospects are exciting, but the realities cannot yet be delivered. During this era, through a series of vehicle fleet replacement cycles, the system will have an opportunity to improve rather than degrade. Ultimately it might deliver traveller services which could exceed the convenience of the car at all times of day, offering spontaneity of use, tailored journeys, and high passenger transfer rates.

Important considerations associated with each timeframe are elaborated below.

3.1 The Present

The dispersed nature of rural and semi-rural residential development patterns around Cambridge means that most out-of-town commuters will continue to start their morning commute using their car even when a city-wide mass transit system becomes available. The mass transit system, at the time of launch, must therefore offer a very clear advantage over the car if the traveller is to be tempted to change mode at the first point of journey intersection with the new public transport system. In brief, the defining characteristics of the public transport system must be:

• Journeys that are highly predictable and reliable (meaning they must run on a 100% segregated pathway because they cannot be subject to the congestion uncertainties which arise from mixing with normal road-going traffic)

• Departures that are frequent (at least every 2-3 minutes at peak times, just like the London Underground, where no-one worries about a timetable)

• Journey times that are fast (very much quicker than remaining in the car, otherwise why would you bother to change mode?)

• Services which are attractive, offering clean, modern vehicles, well designed interchanges, and a variety of system-wide passenger services including wi-fi.

And all of this must be delivered at around half the price of a conventional LRTy.

The key to achieving this infrastructure price target is to minimize the scale of the infrastructure (tunnel diameters, station dimensions, etc). Previous studies suggest that, if the infrastructure is designed in this way, the whole-life cost of the system, over 35+ years, could be funded with little or no public subsidy (see appendix 1). The studies show this can be achieved using vehicles which are either driven by human drivers, or operated under completely autonomous control. If human drivers are present the operating margins are reduced, but the technology risk is eliminated. This makes a very attractive starting proposition.

3.2 The Future

It is likely that the manufacturers of road-going vehicles, particularly cars, will develop highly sophisticated autonomous control systems within the next two/three vehicle generations (10 - 15 years). Most informed observers agree that vehicles with embedded SAE Level 5 autonomy will be commonplace by 2040.

Over the same period we can expect fleet control systems and personalised journey planning Apps to combine to make the spontaneous use of multi-modal public transport a convenient reality. Flexible services, combined with short waiting times and very high passenger transfer rates, would be a transformative public transport offering.

Delivering spontaneous, tailored, journeys requires a high degree of operational agility. This points to the use of small shared-journey vehicles rather than large ones. Small vehicles will allow tailored journeys to be offered, even if the traveller begins the journey from a location which is not on the fixed infrastructure network. In future, a journey might begin with passengers being collected by SAE Level 5 road-going vehicles from random locations far outside the perimeter of the fixed infrastructure. These vehicles would then ‘collaborate’ to form chains of vehicles (convoys) as they enter the fixed infrastructure network. In this way, the system could offer a far higher quality of service whilst continuing to deliver the high passenger transfer rates which are required to serve the City during peak travel times.

Future vehicles might be mainstream products coming from the major vehicle manufacturers, or low-volume products built to order for the transit system operator. Either way, the fixed infrastructure needs to be designed with the possibility of these smaller vehicles in mind. This will raise some particular issues with regard to station design.

Future vehicles might be mainstream products from the major manufacturers, or they might be bespoke products, built to order

The right hand picture shows a 6m concept vehicle capable of carrying up to 24 passengers developed by Xiaofan Zhang, Engineering Masters student at Cambridge.

4. The case for smaller vehicles

Defining the smallest acceptable vehicle dimensions, and developing the associated station designs, requires serious further study. This is far beyond the scope of CAM-TAC, but we have done some preliminary assessments. This work suggests that vehicles should be no bigger than 12m in length and 6m should be considered as autonomous technology improves.

The reasons for this include:

• Saving in infrastructure costs • Greenhouse gas emissions • Novel efficient station design

• Better quality service • Convoys to match demand • Flexibility in using infrastructure • Lower Unit Cost • A competitive market

We examine each these in turn below

Saving in infrastructure costs

Large vehicles mean that the scheme as proposed is not viable (for details see the business model comparison below).

Smaller vehicles mean smaller bore tunnels, roadways and stations leading to savings in infrastructure costs. These savings are substantial and mean the difference between an unviable scheme (as currently proposed) and one that would make financial and economic sense.

Greenhouse gas emissions

Infrastructure based on larger vehicles generates more CO2

By using smaller vehicles, the CO2 tonnes saved in constructing the underground sections is equivalent to the total annual mileage for around 8,000 cars or around 3 years operations for the entire network of existing diesel bus services in and around Cambridge).

Novel efficient station design

Shorter vehicles with four-wheel steering would be able to drive easily into stops set away from the roadway, freeing the roadway for through traffic and saving station stop costs. This could lead to radically different designs at main station stops with major cost savings and potential changes to the network layout. (design: Xiaofan Zhang)

Better quality service

Most route km on the network will have fewer than 1000 passengers per hour in each direction. If large vehicles are used than this would mean either long intervals between services or vehicles running nearly empty

Smaller vehicles (light blue line) enable more frequent services with waiting times of a few minutes

Flexibility in using infrastructure

Station design can start with larger vehicles if that is necessary and accommodate smaller vehicles as the technology becomes available.

There is no need for large scale tunnels and road ways, and stations can be made much smaller.

Convoys to match demand

Small vehicles (light blue) might be convoyed before entering stations in order to provide capacity on more heavily used routes whilst still being cost effective on thin routes.

If larger vehicles are used then they have to be used no matter what the demand in passengers per hour leading to higher operating costs and poorer services

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A competitive market

Shipping containers come in two main sizes: 12m and 6m These could be used for either a 12m or 6m vehicle.

This means that it would be much easier to manufacture and send anywhere in the world, and a more competitive market with lower costs and more rapid innovation would be possible.

Lower unit cost The higher the cumulative volume of production the lower the cost per unit produced. By using many small vehicles rather than a few large ones the unit cost can be expected to fall more rapidly.

Low unit costs mean there is a greater chance that the system will be adopted elsewhere creating the potential for a low cost mass market

(see https://policonomics.com/lp-cost3-learning-curve/)

In Summary

In the longer run, smaller vehicles of the kind illustrated mean lower cost infrastructure, better services, fewer greenhouse gas emissions, more rapid innovation and lower unit costs. (design: Xiaofan Zhang)

5. A Simple Business Model Comparison

A simple cost comparison of the CAM TAC alternative approach compared to the costs outlined in the Steer Report and adopted by subsequent consultants highlights the major savings to be made in infrastructure from taking a smaller scale approach.

The large vehicle approach advocated by the Steer report and endorsed but subsequent consultancy studies leads to an infrastructure cost which is over £4Bn compared to a smaller vehicle strategy which would cost between £1.1Bn and £1.6Bn.

Table 1: A large vehicle strategy results in £4Bn of infrastructure costs compared to a smaller vehicle strategy of between £1.1Bn and £1.6Bn

The Steer Report used infrastructure costs from major projects which are much larger in scale, specifically in the width of the vehicles and the size of the tunnels2.

2 Page 91: The capital costs have been benchmarked against other comparable infrastructure schemes, such as Crossrail and the Northern Line Extension.

CAM TAC Low

CAM TAC High including 60%

uplift SteerOverground Cost per km 4.0 6.40 16.3 Underground cost per km 24.0 38.40 111.7 Cost per Underground station 50.0 80.00 245.0 Underground km 15.0 15.0 15.0 Overground km 104.0 104.0 104.0 Underground cost 360.0 576.0 1,675.0 Overground cost 416.0 665.6 1,693.5 Number of underground stations 2.0 2.0 2.0 Underground station cost 100.0 160.0 490.0 Cost per overground station 0.5 0.8 #N/ANumber of overground stations 40.0 40.0 #N/AOverground station cost 20.0 32.0 #N/ADepots etc 40.0 40.0 40.0 Charging infrastructure 20.0 20.0 20.0 Scheme devleopment costs 100.0 100.0 100.0 Total infrastucture cost 1,056.0 1,593.6 4,018.5

The CAM TAC alternatives have used the guided busway costs and underground tunnelling costs for 4m diameter tunnels. The smaller cross section allows for significant savings in underground station costs as well.

The differences between the CAM-TAC and Steer costs are due to the smaller cross-section of the tunnels and the roadways with linked savings in station infrastructure costs (though we note that the Steer report does not cost over ground stops separately).

The CAM-TAC costs are based on the actual costs of the guided busway (taking the Great Ouse Viaduct structural repairs as exceptional). The underground costs are based on other similar tunnels (at around 4m diameter) with an additional 50% as margin. The CAM-TAC costs are then uplifted by a further 60% to compensate for optimism bias.

The Steer infrastructure costs are based on Cross Rail and the Northern Line extension, both of which are well beyond the scale of what is required to deliver the CAM.

The difference in costs between the two approaches is also a difference in viability.

The difference in infrastructure costs makes a significant difference to the business case. Assuming 30m journeys a year, the costs provided in the Steer report and adopted by subsequent consultants’ work indicates that even in 2051 annual losses would be running at over £100m per year and would require a subsidy equivalent to £3.50 for every journey. The operating costs of the two systems would be roughly similar. The difference is in the cost of the infrastructure (which here has been represented as an annual cost with 3% cost of capital and a 50-year repayment period). Both cases are shown with 30m journeys per year at an average revenue per journey of £2.50.

Table 2: The CAM-TAC approach is the only one that makes financial and economic sense

The main difference is in the cost of infrastructure. At 3% cost of capital and repayment over 50 years the large vehicle strategy has annual financing costs which are 2.5 times that of the smaller vehicle strategy.

In addition, the large vehicle strategy bakes in technological inflexibility as it requires vehicle depreciation of 15 years. The CAM-TAC strategy has vehicles depreciating in 8 years, so 6-7 generations of vehicles can be deployed over the lifetime of the project enabling rapid development and adoption of new technology. This extra flexibility can probably be achieved for the same operating cost.

Business Model (£M) CAM TAC SteerRevenue (2051) £75.00 £75.00Infrastructure Financing costs £60.13 £151.63Operating costs £27.65 £27.86Total Costs £87.78 £179.49Net (£12.78) (£104.49)Net per journey (£0.43) (£3.48)

6. Demand Forecasting and Flexibility

The CAM-TAC has expressed concern about demand forecasting at each of its meetings. It would have been more prudent to provide estimates of demand before costing out large-scale infrastructure.

The CAM_TAC understands that demand estimates currently being developed although these have not been presented. We are however appraised of previous work using these models. Table 3 shows the models estimates for the numbers of cyclists crossing different points in the City of Cambridge. The errors range up to 106%, with most errors in the range of 30-40%

Table 3: There are significant errors in the models being used by the Local Authority to forecast cycling data

Errors for the passengers arriving and departing at Cambridge Station are even larger, and consistently underestimate passenger numbers between 50 and 100%.

Table 4: The errors for estimating passenger numbers at Cambridge Station using the CSRM-2 model are even greater than those for cyclists

A reappraisal of demand forecasts is essential. We have had the major shock of the COVID pandemic and a significant change in transport patterns away from public transport and towards private cars and bicycles. The emergence of the e-bike (which in some parts of Europe now accounts for over 50% of all bike journeys and has changed travel patterns) will be significant.

The use of remote meeting technology has accelerated dramatically over the past two months, and in the words of many observers has brought 5 years of change in 5 weeks.

There should be a major rethink about how to model the demand for the system and to use the results of these studies to determine what kind of system should be designed and built.

7. Findings 1) The scheme, as currently defined, will be unnecessarily expensive to construct. It will

prove to be unaffordable. 2) The scheme does not anticipate future developments in vehicle and operational control

technologies. Such developments offer the possibility of providing ‘agile’ public transport services, a transformative development which could combine flexibility with high capacity.

3) It would be prudent to consider the use of various vehicle types at the early design stage (now) and a plausible roadmap for their future development. Whilst the first generation of transit vehicles may be relatively large (more like a small bus than a car) future transit vehicles may be more like a car than a bus.

4) Adopting smaller vehicles in future will pose no problems for tunnels with conventional road surfaces. But the opposite is true for stations. Some particular thought needs to be given to accommodating different vehicle types within one common station design.

5) The approach to demand modelling needs to be rethought in the light of evidence that existing official demand models are inaccurate and transport patters are changing rapidly. The system should then be designed to accommodate a wide range of demand outcomes, and once again this points to the use of smaller scale infrastructure and smaller flexible systems.

Appendix

A1. Reducing the Cost of LRT

The biggest cost of any segregated mass-transit system is associated with the infrastructure on which it runs. This infrastructure is expensive, but essential, because it provides the protective corridor which separates the mass transit system from normal road traffic. This is necessary if we are to guarantee those fast, frequent, reliable services.

The first, and most important, area for cost reduction therefore lies in the design of the physical infrastructure. This can be reduced from the cost levels typically associated with LRT by taking the following key steps:

• Remove the need for track-side power systems. This can be done by adopting battery-powered electric vehicles, a practice which has been well demonstrated in recent years by the introduction of electric buses in several UK cities.

• Remove the need for fixed guide-rails in the road surface. This can be done by reverting to conventional road surfacing and the use of rubber-tyred wheels. Vehicle guidance can be provided by electronic lane-following systems of a type which are becoming increasingly common in the automotive industry. In addition to reducing the construction cost, removing the rails leads to huge simplifications in the installation process (e.g. the need to re-route sub-surface utilities), thus minimising the surface disruption during construction.

• Remove the need for track-side signalling systems. All vehicle control functions should be handled by vehicle-based sensing and decision-making systems (again, using systems which are becoming increasingly common in the automotive industry).

• Reduce the size of the vehicles. The cost of the infrastructure is broadly related to the size of the infrastructure. This applies generally, but it is particularly true for tunnels and elevated sections. Slimmer, lighter, vehicles require smaller, cheaper, infrastructure.

The combination of these steps leads to significant reductions in the estimated cost of infrastructure. All costs are system specific, but the generalised cost of AVRT infrastructure is intended to lie in the range £15 - £20M per two-way km, compared to the range £25 -30M (or more) per two-way km which is typical of conventional LRT systems.

Another area for cost reduction lies in the operational aspects of the system. Taking advantage of the on-board electronic control systems on the vehicles means that driverless technology can be introduced. In removing the driver cost, this step allows a service approach based on the frequent despatch of relatively small vehicles (e.g. ‘packets’ of 20 - 50 passenger capacity), rather than the infrequent despatch of much larger vehicles (e.g. packets of 120 – 200 passenger capacity). This makes it possible to provide a very high quality peak-time service to travellers, without locking-in over-capacity during less busy times of day.

The combination of low capital costs and low operating costs has the potential to make a light mass-transit system economically viable – fundable in its entirety by private enterprise or, at worst, funded with far less recourse to the Public Purse than is normally the case for fixed infrastructure transport systems.

A2. Case Studies

The potential benefits of light mass transit have been explored in several city-specific case studies.

5.1 Cambridge

An Advanced Very Rapid Transit (AVRT) concept was proposed for Cambridge as the result of a previous appraisal of future mass transit options for the city. The conceptual design of this system was governed by the mantra of ‘compact infrastructure’, because the costs of any fixed infrastructure transport system are dominated by the construction cost of the segregated pathway. (The cost of the vehicle fleet, by comparison, is a secondary issue).

5.1.1 Infrastructure Costs

Tunnels and subsurface stations are the most expensive parts of the infrastructure, so there was an imperative in the Cambridge study to minimise the size of these elements from the outset.

The cost of boring a tunnel is related, amongst other things, to the volume of material extracted. So the effect on construction cost of having a vehicle with a small cross-sectional area is very marked. A cross-section of the AVRT vehicle is shown below, and the tunnel sizes associated with AVRT, a conventional single-deck bus, and a conventional tram are also shown.

AVRT Cross-Section Dimensions

Indicative Tunnel Dimensions to be Associated with AVRT , Single-Deck Buses, and Trams

The dimensions of the tunnels and sub-surface stations developed for the Cambridge study were based on the smallest practicable limits consistent with the passenger transfer rates which were estimated using the Cambridge Regional Transport Model. A ‘sense check’ on practicality was provided by reference to the Glasgow Subway – the smallest metro system operating in a major city anywhere in the world. The Glasgow Subway has 3.4m diameter tunnels and 40m platform lengths in sub-surface stations constructed at a depth of between 8-12m. The proposed AVRT solution had 3.7m tunnels and 35m platform lengths at a similar depth.

The capital cost for the total system (segregated pathways, tunnels, stations, vehicles, etc) was estimated to lie in the region of £700M. A breakdown of the individual cost elements is provided later in this Appendix.

The aggregated operating costs and capital repayment costs were estimated to lie in the region £45M per annum (assuming the borrower can take advantage of Local Authority lending rates over a 30-35 year repayment period).

5.1.2 Economic Viability

The sub-regional transport model showed that around 125,000 in-bound travellers cross the city boundaries during each 24-hour period, with similar numbers travelling out-bound. Using the mode conversion rates experienced in other UK and overseas cities where mass transit systems have been introduced, the estimated daily ridership could rise to around 30,000 passengers per day, most making a two-way commute (i.e. 60,000 individual journeys).

Based on this usage rate, and a very simple flat-fare structure of £5 per day (single payment, unlimited journeys), revenues from the fare-box alone would be in excess of £45M p.a. This is in the same order as the annual sums required to repay both the capital and operating costs as referred to above. This is a very unusual outcome – most fixed-infrastructure transport systems struggle to cover the annual running costs alone.

5.2 Milton Keynes and Oxford

Following the initial Cambridge system definition study, further AVRT studies were commissioned by the cities of Milton Keynes and Oxford. The system layouts developed for those case studies are illustrated below. The Milton Keynes solution comprised approximately 58km of two-way pathway and the Oxford solution comprised approximately 62km of two-way pathway.

It was estimated that each system could be delivered at a price in the region of £15-20M/two-way km (including segregated pathways, stations, communications/control systems, stabling/maintenance facilities, and vehicles).

A series of computer-generated images developed as part of the Milton Keynes study is presented at the end of this Appendix.

A3. Summary of Costs

Infrastructure

Segregated pathway at grade £4M per 2-way km

Segregated pathway in tunnel £24M per 2-way km

Terminus station (at grade, with vehicle chargers) £4M

Pass-through station (at grade) £2M

Pass-through station (underground) £50M

Vehicles Purpose designed electric bus - estimated price for a 50-vehicle order = £600,000 per vehicle

8-wheel drive, 8-wheel steer Bi-Directional Operation

Cruise Speed = 160 km/h Passenger Capacity = 60 (24 seated) Length = 14m Height = 2.5m Width = 2.00m Laden Vehicle Weight = 16 tonnes Battery Capacity = 150 kWh (Lithium-Titanate batteries) Energy Consumption (at cruise) = 2kWh/km Max. Power = 500kW Tyres (rated at 100mph; 2 tonnes per tyre) = Continental 285/65 R16

A4. Visualisations

Pathway at grade running alongside an existing grid road (Milton Keynes)

Elevated pathway running through the city-centre (Milton Keynes)

Elevated AVRT terminus in Station Square (Milton Keynes)