To ask the Secretary of State for Northern Ireland further to his answer to the hon. Member for Antrim, South on 13 January, Official Report, column 482, if he will list the specific measures being taken by Ulsterbus and Citybus to reduce exhaust emissions during their maintenance of buses.

I am advised by the managing director of Ulsterbus and Citybus Ltd. that as a routine part of the vehicle maintenance programme oil samples are taken from engines and subjected to spectographic analysis. This identifies at an early stage engines not functioning properly and enables remedial action to be taken.