22.20 The overall length of the marking (using the word "SCHOOL") must not be less than 25.56 m nor more than 43.56 m. When the word "SCHOOL" is replaced by "CHILDREN", the maximum may be increased to 44.545 m. When the word "SCHOOL" and the short longitudinal line following it are omitted, two additional 3 m zig-zag modules are used symmetrically to give a minimum length of marking of 25.25 m. The overall length may be increased in increments of 6 m by the addition of a complete zig-zag module on each side up to the appropriate maximum. Further details may be found on the working drawing (see para 1.17).
22.21 The length of marking needs to be restricted to one which drivers will respect. Where an authority needs to mark a length greater than the maximum of 43.56 m, e.g. where the school is in a cul-de-sac or the marking is to extend across two entrances which are some distance apart, then two markings, varied in length if necessary (see para 22.20), may be used; they should be separated by a nominal gap of 100 mm. This will ensure that the legend is repeated at adequate intervals. When the marking is mandatory (see para 22.24) upright signs will be needed with each separate marking.
22.22 Where a larger gap would be safe, allowing at least 7 m between the two markings would provide a place for setting down children on their way to school. However, this might also encourage further vehicles to stop behind the first, and undermine compliance with the KEEP CLEAR marking.
22.23 The markings should not normally be placed on both sides of the road, but only on the side on which the entrance is situated. However, conditions may sometimes require otherwise, e.g. where there are school entrances on both sides of the road, or the road is so narrow that not to prevent parking on the opposite side to the school entrance is considered hazardous, or a patrol operates at that point.
22.24 The KEEP CLEAR marking is legally enforceable only when used in conjunction with an upright sign to diagram 642.2A and backed by a traffic regulation order. However, without regular enforcement action, the mandatory version is unlikely to be any better respected than the advisory marking.
22.25 When the mandatory marking is used on a road where waiting restrictions apply, the yellow lines to diagram 1017 or 1018.1 are needed only if a restriction on the same length of road applies at times other than those covered by the stopping prohibition. If the KEEP CLEAR marking is advisory, yellow lines will always be needed if a waiting restriction is in force. The lines will be positioned
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