Twelve Carousel buses have been upgraded in a bid to reduce harmful nitrous oxide emissions.

The £200,000 investment in retrofitting the vehicles’ exhausts with after-treatment technology will hopefully help improve air quality across Bucks.

The upgraded vehicles have gone into service on the Chiltern Hundreds services between High Wycombe, Beaconsfield, Gerrards Cross and Uxbridge.

The buses will operate on the 101, 102, 104 and 105 routes. It will take the number of Euro VI buses in the Carousel Buses fleet to 28, more than 50 per cent of the total fleet.

Phil Southall, managing director of Carousel Buses, said: “This significant investment is a positive step forward in our on-going commitment to introduce more sustainable modes of transport. The introduction of more ultra-low emission vehicles will further help improve air quality in our communities.”