The number 23 route circling between Portsmouth and Havant has a whole new fleet of low-emission buses in a £2m investment by Stagecoach and Portsmouth City Council.
The 18 Surf and Save branded buses, costing £115,000 each, emit a third of the pollutants that their predecessors did.
The new fleet was unveiled on the busy route yesterday by Andrew Dyer, regional managing director of Stagecoach, and Councillor Lynne Stagg, the city council's member for traffic and transportation.
They battled the elements with promotional surf boards to deliver the greener travel message.
Mr Dyer said: 'These buses use the latest technology in pollution reduction.
'They use a compound in the exhaust system which gives you a dramatic improvement in the amount of emissions that they produce.
'If you take into consideration the number of people who can travel on a bus, it helps cut emissions even further.
'Travelling by bus is a lot better than car – it's not only a cleaner way to travel but costs a lot less.
'A resident in Portsmouth travelling to work and back every day can buy a weekly travel card for £10.50.'
He added: 'Forgetting petrol costs, just parking your car in the city costs more than that.'
Cllr Stagg added: 'I'm really pleased to be here and help launch the new fleet, which is on one of the priority bus routes in Portsmouth. I appreciate there's still some congestion in Portsmouth, and I'm looking at ways of reducing that problem.
'The new buses are clean and cool.
'That is the message we have to get through to people – it's cool to travel by bus – and I wish Stagecoach the very best with their new fleet.'
The new buses have also won praise from Dr Caroline Cahm, president of Bus Users UK.
Dr Cahm, who lives in Southsea, said: 'The relatively clean buses are a very big step forward and it is important to make our buses as clean as possible if we are to encourage more people to travel by public transport.'