First Glasgow today unveiled the first 75 buses of a £100 million cleaner-engine fleet required to comply with Scotland's first low emission zone next year.
The vehicles, which have the most up-to-date diesel engines, will be among the one in four buses that will have to have them to enter the zone in Glasgow city centre from 1 January.
FirstGroup, which operates the city's biggest bus fleet, said it would cost nearly £100m to buy or convert buses so all those in the zone are at the Euro 6 engine standard.
The proportion of buses with such engines will have to increase progressively to 100 per cent by the end of 2022.
This will involve replacing or converting 450 of First Glasgow's 850 vehicles at a cost of up to £230,000 each.
However, most of the firm's buses have more polluting engines and there are fears more of these will now operate in other areas of Glasgow and beyond.
The city council said other vehicles, such as cars, taxis, vans and lorries, would have to have the cleanest engines to drive in the city centre by the end of 2022.
Low emission zones, or LEZs, are also planned for Edinburgh, Aberdeen and Dundee by then.
The Aberdeen scheme - where First is also the city's main operator - will cost it up to a further £25m in new buses.
In Edinburgh, where First has a higher proportion of Euro 6 buses already, it hopes Scottish Government grants will cover the cost of retrofitting vehicles.
The first of the new yellow, white and blue Glasgow double deckers, costing a total of £14m, are being built by Falkirk-based Alexander Dennis Limited.
They will initially go into service initially on the 75 route from Castlemilk to Milton from tomorrow.
They feature USB charging points, leather seats and free wi-fi.
One of the buses is also among the first in the UK to have cameras instead of wing mirrors, which give drivers a clearer view via cab screens, and eliminate the risk of collision with trees, other objects and alighting passengers.
"Stop start" technology means the bus engine automatically switching off when the doors are open at bus stops, reducing exhaust fumes inhaled by people on the pavement.
First Glasgow managing director Andrew Jarvis said: "These new buses are just the start of wide-scale improvements we are making to improve our services and provide a better standard for everyone in the city.
"Hopefully, even more people will now sample our new buses, then see it as a real viable alternative to using the car."
Anna Richardson, the city council's convener for sustainability and carbon reduction, said all Glasgow's bus operators would be compliant with the LEZ restrictions when it comes into force without the need to curtail services.
She said: “Glasgow’s low emission zone (LEZ) will reduce harmful vehicle emissions and make our vibrant city centre a safer and more pleasant place to be.
“The bus industry has worked closely with the council to ensure delivery of the first phase of the LEZ.
“Partnership working is key.
“Whilst the first phase of Glasgow’s LEZ applies to local service buses only, we’re committed to improving air quality, and by the end of 2022, the strict exhaust emission standards required to enter Glasgow’s LEZ will apply to all vehicles.”
Ms Richardson said: "It's really important to give people those four years to prepare."
Transport secretary Michael Matheson said: “We are providing support for operators, including First Glasgow, to push beyond normal diesel to greener technologies through the Green Bus Fund and Bus Service Operators' Grant."
Friends of the Earth Scotland said the new pollution controls had spurred First Glasgow into accelerating its bus clean up.
Air pollution campaigner Gavin Thomson said: "Buses are a vital part of the solution to Glasgow’s air pollution problem and it’s great to see the LEZ forcing the company to act.
“Older buses can be amongst the worst polluting vehicles, and the sooner we get rid of these dirty vehicles, the easier we can all breathe.
"There are 300 early deaths a year in Glasgow due to air pollution.
"We hope all bus companies act with the urgency this public health crisis needs.
However, Glasgow’s LEZ is very weak and asks only that bus companies make incremental, year-on-year improvements to their fleet."