In the United Kingdom, driving examiners are civil servants employed by the Driver and Vehicle Standards Agency (DVSA) in Great Britain and by the Driver and Vehicle Agency (DVA) in Northern Ireland for the purpose of conducting the practical element of driving tests. Outside the military, haulage and private bus companies who employ delegated examiners who test their own drivers, driving examiners are the only people who are authorised to conduct driving tests and issue the certificate required for obtaining a full driving licence in the UK. Driving examiners do not conduct the theory tests as these take place in an office environment, supervised by administrative staff. Organisation There are over 1,600 driving examiners in the UK, working at over 400 test centres. Driving examiners may be full or part-time, conducting anything from 35 tests a week (full-time) down to 14 tests a week (the current part-time minimum). Overtime is available when there is demand, which is more or less constant in all but the quietest of locations. Not counting trainees, there are three job roles associated with the Operational Delivery of Driving Tests - Driving Examiner (DE), Local Driving Test Manager (LDTM) and Operational Delivery Manager (ODM). Test centres are grouped into sectors with each sector headed by a LDTM, with the ODM heading a large geographical area of test centres. Mark Winn is currently appointed as the Chief Driving Examiner for the whole country, although the Chief Driving Examiner is not the head of the DVSA with several layers of non-examiner management and executive staff additionally employed. Vehicles tested All driving examiners start as (only) car examiners, since car tests represent by far and away the highest demand. The most common additional vehicle tested for is the tractor. Category F testing can be done with a standard licence holder as it is a given entitlement when passing a car test. Large Goods Vehicle testing is a close second due to operational demands. The current motorcycle test involves off-road testing so candidates normally have to go to a purpose built testing centre (this is under review). The DVSA certifies examiners for every vehicle that a licence can be issued, however, so examiners exist to cover everything from the moped to tracked vehicless. Special tests Beyond what are known as the "L" tests (ordinary driving tests for any given vehicle), driving examiners also conduct various special tests including the extended