They’re called trains.
It’s now 60 years since the first electric trains arrived in Scotland, revolutionising rail travel by replacing steam on suburban routes in Glasgow – and smoky subterranean platforms - with zero emission comfort.
The fondly-remembered “Blue Trains” were a dramatic new feature on the country’s rail landscape, their former Caledonian Railway livery standing out from British Rail’s then maroon carriages.
A blue and yellow double arrow logo designed to promote the service even influenced the creation of the BR symbol which is still used for stations, and is to be updated for the UK Government’s new Great British Railways body that is due to take over the network.
Since then, electrification has covered most lines across Glasgow – Britain’s biggest urban network outside London – and all five routes between there and Edinburgh too.
It means three in four ScotRail journeys are on zero-emission trains – a far higher proportion than on any other motorised transport.
The Scottish Government has plans to complete the job, with a “decarbonisation action plan” that would see all diesel trains scrapped by 2035.
They are to be replaced by electric trains using either traditional overhead wires or batteries, and some running on hydrogen.
This will be a significant change, as anyone who has travelled on ScotRail’s newest electric fleet that has taken over from diesels on the Edinburgh-Glasgow main line will have noticed. The trains are cleaner, quieter and accelerate faster.
But, as I’ve mentioned before, it’s ironic when the fumes from the operator’s oldest diesels are sucked into the air conditioning systems of the new electric carriages as they pass each other in tunnels.
Two of the remaining Glasgow routes to be electrified, to Barrhead and East Kilbride, will be completed next.
Then it will be the turn of the Fife Circle, which is due to be operated by battery trains that recharge as they travel over electrified sections of the line.
It was announced this week that the next addition to the Scottish rail network, the Levenmouth route from Thornton to Cameron Bridge and Leven in Fife, due to open in 2024, would also be electrified from the start, ready for battery trains when they become available.
Unlike its Borders Railway predecessor which was not electrified - although future-proofed to enable it - the Levenmouth route decision is a key line in the sand towards making the network even greener.
But the task is huge.
Network Rail said it would involve electrifying more than 1,000 miles of track – the equivalent of completing the Stirling-Dunblane-Alloa electrification scheme every year for the next 14 years.
Electrification will extend as far as Aberdeen and Inverness with hydrogen trains to run on remoter Highland lines.
When the 2006 smoking ban was introduced in Scotland, major stations started smelling of diesel fumes rather cigarettes.
Fifteen years on, we’re on our way to also ridding the country’s railways of those equally toxic emissions.
It will also keep them ahead in green credentials compared to the still tiny proportion of electric and hydrogen vehicles on the roads.