For total life cycle comparisions see here: https://bathtrams.uk/relative-life-time-co2-enissions-of-tramways-compared-to-buses-and-busways-taking-into-account-co2-during-construction-ie-steel-and-concrete-etc/
- Info from Professor Lewis Lesley:
Above: A bombardier tram in the 10th district of Vienna, Austria
2. Alternative calculation.
Trams are a seemingly expensive outlay for a city. They require permanent tracks and overhead wires. At least that’s how the figures can often initially appear, but there is more to it than basic installation cost. What of the energy required to operate, maintain and recycle our transport network. Once installed trams are one of the lowest energy and most sustainable mass transit systems a city can operate. Much lighter than trains, without the need for often cost prohibitive and energy-intensive underground tunnels that a metro system requires. Trams run on hard wheels and rails that can be fully recycled and have much lower rolling resistance than soft rubber tyres. They are plugged directly into the mains, negating the need for energy and resource intensive batteries that need their own separate and often more expensive charging infrastructure. full brilliant article here:
Below is a breakdown comparing trams and buses. Because the length of trams can vary, a single carriage, which is also comparable with the weight of a double-decker bus, has been used in these calculations. In reality, a three-car tram can carry as many as 140 passengers, standing and seating, compared with the new electric London buses, which propose to have a capacity of 90.
The main characteristics affecting energy consumption are rolling resistance, drive efficiency, drag coefficient and frontal area and weight.
Summary of approximate energy needed to move a tram and a diesel and electric double decker bus 5km in kWh
the above figures produce the following kWh per passenger km:
Diesel Double Deck Bus 0.48
Electric Double Deck Bus .182
For trams (& trains) the rolling resistance is much less than rubber tyres on tarmac (coefficient c 0.002 v 0.01.). Picking up Bob Chard, all tram regeneration systems must monitor the receptivity of the OHL, to prevent the voltage going above the safe limit. Normally on an urban system there are enough trams drawing power to use regeneration power.
On railways it is possible to timetable trains so that one going down hill can power one going up hill. The idea is not new, since the central tube line in London was built (1900) with tunnels downhill from stations and uphill into stations, as mechanical regeneration.
Finally when trams in London were converted to trolleybuses between 1935 – 1940, despite the new trolleybuses being lighter (12tonnes) compared to the 30 year old trams (18tonnes), sub-stations had to be strengthened as the trolleybuses used > 3 times more power due to much higher rolling resistance. Yes energy in transport is critical, as it uses over 80% of all UK oil consumption, and over 99% of transport is oil powered. Thankfully trams running on (renewable power) are zero oil consuming, and therefore zero CO2 and toxic pollution. – Lewis
I agree there is no substitute for direct measurements, however the article I wrote was on the back of my thesis on microsimulation traffic modelling and discussions with local authorities trying to try to turn the focus of transport planners to energy consumption, rather that journey time, congestion and short term economics. Energy is rarely considered in transport planning, yet it is energy that largely determines exhaust and non-exhaust emissions, noise, injuries and also fuel cost. Some simple mechanics would go a long way to demonstrating the most cost effective option, but this is not happening.
It is not true that rolling resistance is insignificant at low speed. Once rolling resistance has been overcome (at around 20mph) the energy remains constant. This is the reason the most energy efficient cruising speed for a Tesla is 20mph. For urban movements of large vehicles rolling resistance is significant. There are also considerable environmental benefits of metal wheels and rails over rubber/plastic/tarmac which are also important considerations in transport policy.
I understand that regeneration is a significant part of electric vehicles braking. However, I didn’t initially realise trams can’t ‘dump’ the electricity back to the grid and require a battery for regeneration to be possible. It is my understanding an electric car can only recover around 50% of the kinetic energy from this process? I presume one of the reasons Swiss trams go faster uphill than down is to maximise the regeneration efficiency? I was fascinated to learn the Kiruna/Narvik train operates almost entirely energy neutral thanks to regeneration downhill with a full load of iron ore and using the stored energy on the return journey uphill with empty carriages. – Blaise
Or see this:
Steel Wheels or Rubber Tires?
Railroads Produce Less Ground Friction Than Motor Vehicles
First, think about some simple physics. A turning steel wheel in contact with a steel rail reduces by 85-99% the amount of rolling friction than a rolling rubber truck tire has in contact with an asphalt or concrete pavement. [Nice, Karim, How Tires Work, HowStuffWorks.com, http://auto.howstuffworks.com/tire4.htm] The train wheel’s reduction in friction over a car tire is even greater. Much of a car’s gasoline bill goes into bending and wearing out tires. Feel your tires after a trip. They are hot, and that heat was produced by repeatedly bending them and rubbing them on the road. Car or truck tires flatten into four “footprints” as each meets the pavement when the wheels turn. The tire sound made at highway speeds is mostly a consequence of tires quickly compressing against the pavement and decompressing as they spin. Auto drivers paid for the gasoline to bend, unbend, and re-bend those tire thousands and thousands of times. Truckers pay in diesel………
Extract from: https://steelinterstate.org/topics/steel-wheels-or-rubber-tires