After UK Transport Secretary Chris Grayling said that the decision to scrap electrification between Cardiff and Swansea was taken on a “simple basis”, Jenifer Baxter — head of engineering at the Institution of Mechanical Engineers (IMechE) (www.imeche.org) — commented: “Electrification of this line would bring improved air quality, better energy efficiency of trains, reduced greenhouse-gas emissions and enhanced services.

It is also a stretch of line that is used extensively and provides an economic link between the two main cities in South Wales.

“Unacceptably high costs for the Great Western electrification scheme have been given as the reason for scrapping the scheme, with costs rising from £874 million in 2013 to £2.8 billion in 2015.

“At today’s prices, this is seven-times the cost of British Rail’s electrification of the East Coast route.

“For this reason, the Government has cut back this electrification and wrongly claims that its benefits can be delivered by bi-mode trains.

“Bi-mode trains are designed to operate on both electrified lines and non-electrified lines.

“Those currently being introduced on Great Western and East Coast routes can switch between the electric powered mode and an on-board diesel-powered engine.

“While flexible, the electric-diesel bi-mode train has increased emissions when operating in diesel mode; it also has higher fuel, capital and maintenance costs than pure electric trains — and it is less powerful when working in diesel mode than in electric mode.”

Dr Baxter said that while bi-mode trains offer a solution to non-electrified lines and reduce the requirement to invest in electrifi-cation, they do not provide the required performance or offer the most efficient or environment-friendly solution.

“In our report A Breath of Fresh Air: New Solutions to Reduce Transport Emissions, we recommended that the Department for Transport instruct Network Rail to develop an appropriate specification for railway electrification — one that will achieve an affordable business case for a rolling programme to complete the electrification of main lines between Britain’s principal cities and ports, and of urban rail networks through our major city centres.

“As the pollution in our cities continues to cause health problems and climate change becomes increasingly evident across the globe, this is now an urgent requirement.”