Allow me also include the UK guidelines from
CAP 168 which can be found in
13.5 Declared distances from runway intersections.
Declared distances from a runway intersection shall be calculated from the downwind edge of the taxiway.
Contained within are Figures 3.14 through 3.16 which show that the distance calculated is NOT coinciding with the markings and lines, validating my earlier statement that the lines (in UK) had nothing to do with lineup from intersections.
Furthermore, the document shows that any lead-in lines onto runways are not taken into account for takeoff distances available, merely aid the pilot to position on the runway.
The origin of full-length declared distances is, in most cases, the end of concrete; therefore, following aircraft line-up, the origin is behind the aircraft. An allowance for the length of the aircraft is taken into account when calculating the remaining distance. ICAO publishes the following in Annex 6 Part I, Chapter 5, paragraph 5.2.8.1: "In determining the length of the runway available, account shall be taken of the loss, if any, of runway length due to alignment of the aeroplane prior to take-off." Aircraft performance manuals make the same calculation for line-up allowance irrespective of where that line-up occurs along the runway. Therefore, flight crews would expect to calculate a similar correction distance at an intersection departure as for a full-length departure, regardless of where the origin is located. The use of the downwind origin as the basis for calculating declared distances from a runway intersection provides consistency with the full-length calculation.