Written evidence submitted by Mr D Dundas


1.              What role rail decarbonisation can make to the Government’s wider commitments on air quality to 2040?


Decarbonisation of rail means eliminating all rail carbon emissions by 2040:


By replacing all diesel engines with electric motors, supplied with green electricity, either directly, via batteries, or with batteries backed up by hydrogen fuel cells.             


By converting the heating of railway buildings to green electricity or electric driven heat pumps. The difficult logistics of converting building heating to 100% hydrogen will probably prevent hydrogen heating.


Decarbonising rail will also reduce emissions of NOx and particulates which are harmful to health.


All UK diesel powered trains are diesel-electric with a diesel engine driving a generator that drives the electric traction. A diesel engine is around 35% efficient in converting the energy of the diesel fuel in the stop-start of commuter rail; the generator is about 80% efficient, giving a net overall efficiency of about 28%, so replacing them with electric power will greatly improve energy utilisation.


The electric power can be supplied directly by overhead line equipment (OLE) which are catenary conductors, but the cost of the necessary infrastructure is high, particularly for the existing diesel powered lines where many bridges may need to be rebuilt. The electrification of the London to Cardiff line now stands at £2.8 billion for the 150 miles, or £18.7 million per mile. The maintenance cost of overhead catenaries is also high and they are vulnerable to extreme climate, flying objects and falling trees.


Existing diesel electric trains can be converted to hydrogen-battery (fuel cells) to power the electric traction, one by one, avoiding a huge capital outlay to convert an entire line to OLE. This has already been achieved in the Hydroflex hydrogen conversion of a 319 class train by Birmingham University and Porterbrook (leasing) which ran its first passenger trial recently; I had a ride in the Hydroflex more than a year ago. The Alstom Breeze is a similar conversion of a 320 class train that they plan to start delivering by 2024 from their Widnes depot.















Alstom Breeze


Porterbrook Hydroflex



The gradual introduction of diesel-electric trains converted to hydrogen power could be started immediately without major capital outlays, and if started in the north it would serve as a demonstration of Government commitment to levelling up the regions as well as to decarbonising rail.




Hydrogen powered trains contain batteries between the fuel cells and the traction equipment to provide extra short term power for acceleration, and also to recover and store power during regenerative braking. Because of the weight of batteries and their long recharging time, it is unlikely that a battery only train will be viable for any but very small commuter trains.


Diesel engines also produce NOx and particulate matter, so their elimination from the UK railways will have a direct and positive impact on air quality and the health of our nation.


Decarbonising of UK railways as described above, will depend on converting all UK electricity supply to green electricity from renewables and nuclear power; this might not be achieved by 2040, but hopefully by 2050.


2.              Whether there is adequate financial and other support from the Government for the development of alternatively fuelled rolling stock;


There is no need for further immediate development of alternatively fuelled rolling stock as it is already available. What is needed is a financial commitment for new funds to start leasing the converted and new rolling stock to replace the diesel powered trains.


3.              How the industry is responding to the challenge of a carbon-free transport future by 2040 and developing technologies to achieve that;


Two major suppliers of UK rolling stock: Porterbrook with Birmingham University and Eversholt Rail with Alstom have already developed hydrogen conversions of diesel-electric units to hydrogen-electric which have both completed their trials on mainline tracks.


4.              What challenges there are to deploying alternatively fuelled rolling stock on the GB rail network, particularly given issues with standards and loading gauge;


The UK rail loading gauge (safe clearance dimensions) is a significant obstacle to procuring standard rolling stock from other countries where clearances of fixed objects in widths and heights are greater. (The UK track width (between the inner faces of the rails) is the same as most of Europe at 1,435mm). In many developed countries, train carriages can have double decks which are too high for our lines. The reduced dimensions of the UK loading gauge limits the ability of the UK to increase the width and height of rolling stock on existing lines. Because of the overhead space taken by OLE equipment, if this was removed this would allow the introduction of taller double-deck trains driven by hydrogen power.


The hydrogen powered Alstom Coradia iLint is in passenger service on several lines in Germany, The Netherlands and Austria, but it is too high to pass under many of our bridges as the hydrogen tanks are carried on the roofs of the carriages.


Please see:




Hydrogen powered trains will require a supply of hydrogen at key points on the network. This hydrogen can be produced with electrolysers at the point of use, powered from the grid or where possible by local renewables, such as wind. They can be modular and delivered by road or rail in a shipping container size. A factory to produce hydrolysers is under construction on the Sheffield energy park which is planned to produce a total number of electrolysers having a combined capacity of one gigawatt a year.


              Please see:




A further challenge will be to have enough electric power available where the electrolysers are installed.


5.              What passenger benefits alternatively fuelled rolling stock could provide;


When you take a train journey in a diesel-powered train, you can feel the personal disadvantages in terms of the impact of the emissions of NOx and particulates on one’s health. This is especially noticeable when a diesel locomotive is standing with its engines running in an enclosed station, both for those standing on the platforms as well as those seated inside the train with the doors open. Electric or hydrogen electric powered trains do not subject passengers to these health hazards and will provide a slightly less noisy ride than diesel powered, especially on acceleration.


6.              Whether alternatively fuelled rolling stock would be cost effective compared to EMUs over a 25-40 year life-cycle;


I assume that the question refers to long term costs of existing electric only powered trains, as the alternatively fuelled trains also have electric powered traction. When the high capital and maintenance costs of overhead catenaries, as well as the economic impact of the downtime arising from damage by extreme climate and flying or falling objects are taken into account, EMUs are almost certainly more expensive to run overall. A detailed study of the combined effects over a 25 year period needs to be done.


7.              What the train interior of the future needs to have to ensure continued growth in rail travel, particularly amongst young people and future generations and to be fully accessible to all.


I believe that trains will be used more and more for long distance travel, so the working and leisure public travelling on trains, need to be able to continue their daily life in communication with their business and private contacts with high speed broadband and mobile ‘phones, which will require a much greater improvement in these services on many trains. As these journeys will often be for several hours, other facilities such as toilets, catering, places for storing heavy suitcases and accommodation for handicapped people must see a substantial improvement. The use of commuter trains on fast intercity routes must stop; not only are they uncomfortable to ride in at high speeds but are probably more dangerous than trains designed for this type of travel.



D Dundas                                                                                                 


October 2020