SCOTLAND’S attempts to reduce carbon emissions from traffic are being helped by a new generation of “green” buses, but the effort is being negated by traffic congestion.

The UK’s largest bus operator, Perth-based Stagecoach, says golden opportunities to cut gridlock have been missed, leaving electric, hybrid, gas and hydrogen buses stuck alongside cars, which are often more polluting.

Bus speeds in Glasgow, for example, are declining at a rate of 1.5 per cent each year, a worse figure than London, Edinburgh and Manchester. This means that advances in greener public transport technology are failing to reach their full potential, according to Stagecoach’s engineering director Sam Greer.

Speaking ahead of Scottish Renewables’ first Low-Carbon Cities Conference in Edinburgh next week, Greer said his company’s £90 million-a-year investment in ultra-low emission buses is improving urban air quality – but could do more.

He said: “One of the biggest challenges we face as a bus operator is a lack of road space. It doesn’t matter what technology we bring into the bus market if congestion stays at the same level.

“If road space isn’t freed up then we will still have the same number of cars and same air quality issues. Buses can help reduce the number of cars on the roads and reduce carbon emissions – they’re part of the solution, not the problem.”

Greer highlighted the introduction of bus gates in Glasgow and a bus lane on the M90 into Edinburgh as positive moves.

Jenny Hogan, director of policy at industry body Scottish Renewables, said: “Transport makes up a quarter of the total energy we consume in Scotland, so efforts to reduce carbon emissions from the sector are important if we want to meet our climate targets.

“Cutting congestion and getting people out of their cars must be the top priority, closely followed by adopting new technologies and clean fuels such as hydrogen.

“But replacing petrol and diesel with electricity or hydrogen to power our railways and vehicles is only low carbon if it comes from renewable sources.

“Converting more solar, wind and ocean energy into electricity, hydrogen and sustainable biofuel is the only way to ensure our future transport system is truly clean and green.”