The UK currently boasts 10 urban light rail/tram systems, with a geographic stretch from Edinburgh in Scotland to Croydon in south-east England, and a historic timeline from 1885 (Blackpool) to 2014 (Edinburgh). That number may be about to go up: £2.1bn of government money is to be directed to funding public transport in the West Yorkshire Combined Authority, and the majority of that is to be allocated to creating two new tram lines in Leeds and Bradford in a project worth £2.5bn.

When it comes to creating and meeting passenger demand, the systems are clearly successful. Last year, the original Edinburgh route from the airport to the city centre was busier than ever, and an expanded network saw an increase in 7.3 million passenger journeys compared to 2022 (the year before the system was finally extended to Newhaven).

Over the past year, the system’s operating company Edinburgh Trams has also won the ‘Most Improved System’ category at the Global Light Rail Awards, and the title of ‘Tram Operator of the Year’ at the National Transport Awards.

But this success has come at a significant price. Long delays in building the line saw costs almost double to over £1bn. The cost of moving underground utilities had been under-estimated, but that was far from the only issue.

The four-volume report following the inquiry led by Lord Hardie into the construction of the Edinburgh system actually asked Scottish Ministers to consider whether there was a requirement to allow civil and criminal sanctions on individuals or companies that knowingly submit reports containing false statements to councillors, implying that questionable practices may have occurred.

Lord Hardie also underlined the wider cost of the project to the community. ‘Poor management and abdication of responsibility on a large scale have had a significant and lasting impact on the lives and livelihoods of Edinburgh residents, and the reputation of the city,’ he wrote.

Much-needed urban regeneration had been delayed in Leith and Newhaven, and local businesses had seen their customer base evaporate thanks to prolonged road closures.

There can be no argument that the Edinburgh tram has been a success in attracting passengers but, as Lord Hardie said, Edinburgh Council now faces debt repayment costs amounting to 1% of its total budget for the next 30 years.

Proponents of the bus could argue that they could have achieved almost as much in terms of ridership at a fraction of the cost to the public purse by using road-going vehicles running on corridors with high levels of bus priority.

Tram advocates can counter this argument by pointing out that the construction of a permanent way is a ‘one-off investment’, and that once up and running trams offer a high-quality, low-cost, transit system.

One of the major savings is in energy. Surprisingly, energy consumption is not always a prime consideration in transport planning. However, besides cost, energy consumption also impacts on outputs of pollution, noise and CO₂.

Reduced rolling resistance is one of the key factors in the energy savings offered by trams. The steel-on-steel interface between tram wheel and rail reduces rolling resistance by 80–99% compared to heavy-duty vehicle tyres where the interface is between tarmac and rubber, with pneumatic tyres distorting to conform with the surface, compressing and rebounding as the tyre rolls, and heating up as they transfer torque to the road.

A further bonus for trams is that micro-particle emissions from pneumatic tyre wear are now seen as a serious source of pollution of both air and water. In fact, modern heavy-duty diesel vehicles are now said to produce more particle emissions from their wheels and brakes than they do from their (heavily regulated) engine exhausts. Disposing of, or recycling, end-of-life road surfaces and rubber tyres is problematic, while worn steel wheels and rails can simply be recycled to emerge again as fresh product.

The e-bus advantages
But the balance can swing back in favour of the (pneumatic-tyred) bus, when electric buses replace diesels.

According to data published by Blaise Kelly, an air quality engineer and scientist at Dutch research organisation TNO, in 2019, a tram travelling 5 km and stopping five times would consume 47 Wh per passenger. This compares well to a diesel double-decker bus (76 Wh per passenger) but poorly with an electric double-decker (33 Wh per passenger).

Two factors may account for the electric bus victory. It has a lower unladen weight than the tram, so consumes far less energy under acceleration, and it has regenerative braking, so it can recoup some of that energy when slowing down. Trams could be fitted with regenerative braking, but only by installing batteries which add weight and cost.

Trams and buses both beat cars in terms of energy consumption per passenger mile as well as reducing congestion, but prising people away from their cars is still a great challenge. Here, it would appear, that trams beat buses.

Two factors may account for the electric bus victory. It has a lower unladen weight than the tram, so consumes far less energy under acceleration, and it has regenerative braking, so it can recoup some of that energy when slowing down. 

In evidence given to Parliament in 2005, Transport for London (TfL) said that while what it termed ‘predatory pricing’ from bus companies operating on parallel routes had prevented passengers riding on the then independent Croydon Tramlink from reaching expected levels until prices were harmonised, 19% of Tramlink passengers had switched from cars.

Tramlink was also credited with having reduced local unemployment by up to 35%. Unlike buses, which were predominantly used by ‘poorer’ people, and heavy rail, predominantly used by the ‘rich’, Tramlink was popular across all sectors of the community.

Capital cost was an obvious issue, but TfL pointed out that one tram had the passenger capacity of three buses, and bus speeds were only 55% of tram speeds. Crucially, the tramcars had a projected life of 30 years, while buses were replaced after just six years. It should be noted, however, that the buses are sold on for service outside the capital, while the trams will probably be scrapped after three decades of use, as is now happening with the first generation of Sheffield Supertrams.

Is best of both worlds possible?
It is worth asking whether there is a way of introducing a system that would combine the passenger appeal of trams and light rail with the lower costs and greater flexibility of electric buses.

Enter bus rapid transit (BRT). This entails creating a route with a high level of bus priority (at least 60–70% bus priority lanes and traffic lights) on, or alongside, existing roadways, which can be done at around a fifth of the cost as no rails need to be laid or overhead powerlines installed. This cost reduction also means that a BRT scheme may still be viable where a smaller population means that a light rail solution never would be.

For example, an ambitious travel plan advanced by Stoke-on-Trent City Council this year sees BRT as the core of a scheme which also includes utilising canal towpaths as cycle routes, along with improvements to the West Coast Main Line heavy rail service.

Improved bus priorities bring huge benefits in service frequency, speed and reliability, but these are not always apparent to non-users who must be won over to try bus travel instead of other modes of transport. One of the biggest problems is perception. Modern electric buses are still mostly visually identical to their diesel counterparts, and are tarnished in the eyes of some with the unfortunate image of being poor-quality transport for the economically disadvantaged.

That was a dilemma faced by Kent County Council when it needed a public transport system for the fast-growing towns of Dartford and Gravesend. Now branded as Thameside, it is scheduled to provide 25,000 new homes and 50,000 new jobs in the next 15–25 years. The current road network was ruled unable to cope with the increased population if normal levels of car use were retained, but it was feared that bus priority measures alone, introduced under the Fastrack brand in 2006, would not trigger sufficient modal shift.

An alternative solution
It was for just such situations that the Irizar ie tram was invented. Billed as a ‘tram on tarmac’ it offers the appearance and amenity of a tram with the flexibility and low cost of an electric bus with road wheels. A newly-elected mayor in Amiens, France, realised that his promise of a light rail system could not be delivered in a town with a population of just 150,000. Instead, 90% of the town’s bus routes were given bus lanes, and a fleet of over 40 rubber-tyred, 19-metre-long battery-electric ie trams were ordered from Spanish coach and bus manufacturer Irizar (better known in the UK for luxury touring coaches).

When is a tram not a tram? When it’s an Irizar ie tram electric bus, which are now running in Britain on bus priority routes, such as in Dartford, Kent
Photo: Irizar

In addition to conventional overnight depot charging, the ie tram can top up by ‘opportunity charging’ via gantries at the route termini during the working day, extending the shifts it can work. The ie trams now operate four routes in the town as part of the Nemo network, with another 90 or so conventional buses serving other routes.

With its service provider Go-Ahead London, Kent County Council has introduced 28 ie trams to its key Dartford to Gravesend service, making this key route 100% electric and boosting its passenger appeal while potentially using less energy per passenger than either diesel buses or trams.

• Further reading: ‘Building the business model for decarbonised road transport’. Decarbonising a transport company requires strategic forethought; a clear understanding of customers’ needs to accelerate the selection of public transport as a preferred mode, according to Alex Jensen, CEO of National Express. It also requires the building of strong partnerships, and collaboration across the public and private sectors.
• How exactly is the move to alternative, low-carbon fuels for UK road and rail users going to play out in the next few years? Gloria Esposito, Head of Sustainability at Zemo Partnership, a public-private partnership that aims to accelerate transport to zero emissions, discusses the decarbonisation options for cars and vans, heavy goods vehicles (HGVs), non-road vehicles and the railway.