17.—(1) Subject to sub-paragraph (3), any transparent surface forming part of a rail vehicle which is located in that part of the interior of the vehicle which is accessible for passengers must—
(a)be separated from where a passenger can walk or go in a wheelchair by a seat, table, handrail compliant with paragraph 10 (2) or other fitting; or
(b)bear a coloured marking which must—
(i)be not less than 140 millimetres and not more than 160 millimetres wide;
(ii)extend horizontally across the whole width of the transparent surface; and
(iii)be situated so that the bottom edge of that marking is at a height of between 1485 and 1515 millimetres measured vertically from the floor; or
(c)be bounded on any edge which is not attached to the floor, wall or ceiling of the vehicle by a handrail which complies with paragraph 10 (2).
(2) For the purposes of this paragraph “transparent surface” means a transparent surface which is vertical and, if it forms part of a larger vertical surface, comprises more than 75% of the total vertical surface area of which it forms part (and “vertical” for this purpose means vertical or thereabouts).
(3) This paragraph does not apply to any windows fitted in doors at the side of a rail vehicle or to any other external windows fitted in the side of a rail vehicle.