Page:UK Traffic Signs Manual - Chapter 4 - Warning Signs. 2013.pdf/29

 they think it correct. Instructions should not be given it they are likely to be ignored and any existing signs which are not being respected should be removed.

6.5 "Low gear" plates are not normally used unless the gradient overall or in part exceeds 12% and the hill is longer than 800 metres. They are more likely to be justified where there are also sharp bends.

6.6 The instruction to "Keep in low gear" (diagram 526) should be used at intervals of not less than 800 metres where the gradient exceeds 12%; it may be accompanied by diagram 554.1 "Try your brakes" (see para 11.2). When used in advance of an escape lane, diagram 523.1 should be replaced by 554.1 as shown in table 6-1. Exceptionally, diagram 526 may be used at a shorter interval, e.g. where an increase of gradient is hidden from view.

"Steep hill" signs without plates may be repeated on a hill where the gradient steepens but should not be placed at intervals of less than 550 metres unless the gradient increases by 5% or more.

On long descents, certain sections may be steep whilst others are below the 10% criterion for provision of signs. It might then be better to treat the steeper parts as separate hills and sign accordingly.

Where an escape lane or arrester bed is available, the "Escape lane ahead" sign (817.2) should be used. It should form part of a sequence of signs with "ahead" varied as in table 6-1. The sign may also be varied to show the escape lane to the left on a straight road. Permitted variants are illustrated on the working drawings (see para 1.8). The order of the sign plates, from the top, should be: warning sign (523.1 or 554.1): supplementary plate (525 or 526): diagram 817.2.

The sign shown in diagram 524.1 should be used only:

(i) where the gradient is 15% or more, or

(ii) where the ascent is longer than 1600 metres and the gradient is 10% or more, in which case the sign should be accompanied by a distance plate to diagram 570 (see section 18).

The supplementary plates to diagrams 525, 526 and 527 should not normally be used with the ascent warning, except in rare circumstances e.g. where a very sharp increase in gradient is hidden from view and there is a record of accidents due to vehicles stalling and rolling back out of control.

For signs to diagram 583 and 583.1 (indicating slow-moving vehicles) see paras 20.3 and 20.4. 28