mainline steam locomotives, such as from the need for a yellow warning panel or crumple zones. In liaison with Network Rail, a route acceptance strategy was agreed upon and approval for Tornado to enter service was granted by the Office of Rail Regulation (ORR). This was completed in two stages, approval under the Railway and Other Transport Systems regulations, for use on the GCR and other preserved lines, and then as an "interoperable" locomotive for use on the mainline network. As well as standard tests, as technically a new design of locomotive, Tornado was required to undergo specific extra tests set by the by the Network Rail Safety Review Panel to examine ride quality and track force, in order to assess the effect the locomotive would have on the main line track. Such tests were done in part at the GCR, whereby Tornado ran through a curved section of track at Kinchley at speeds of 10, 20, 30, 40, 50 and , with a trailing saloon car fitted with monitoring equipment, including a GPS unit to measure the precise speed and distance travelled at every metre. Measurements were taken on board by 21 sensors measuring pitch and roll, and acceleration and deceleration. Measurements were also taken through the use of track-side sensors measuring side forces exerted on the rails, augmented with freeze-frame footage of the position of the wheels as they passed. The results were compared with control readings taken at the same site using BR Standard Class 7 70013 Oliver Cromwell two weeks later. The preliminary results were described as producing "no untoward signals".Tornado was granted an Engineering Acceptance (EA) certificate on 31 October by DeltaRail and a Route Acceptance certificate on 3 November by Network Rail, allowing testing on the main line to begin. Further tests were performed at Network Rail facilities located between York and Darlington, at a testing facility known as a WheelChex. This consists of track fitted with sensors to measure vertical force effects such as hammer blow. Completion of a test run between York and Leeds on 28 January 2009 signalled the gaining of certification to haul passengers on the Network Rail main line. In January 2009, the railway press reported that a discrepancy had emerged in the 18 November 2008 test, whereby the OTMR recording equipment on the Class 67 being towed had recorded a top speed of around , while the A1