Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/43

DESIGN CRITERIA protectors are in use at traffic signal sites (see paragraph D5.10.9) and when locally fabricated or prefabricated "humps" are used to protect pipes, cables etc. that are run across the road. Such "humps" should not be of such a design that they are a hazard to road users, in particular cyclists and motorcyclists.

The "RAMP" sign to diagram 7013 is used at the change in level. The gradient and length of the ramp will be dictated by the speed at which vehicles are expected to traverse it. Wherever possible, the ramp should be constructed at right angles to the vehicle path.

The "uneven road ahead" sign to diagram 556 may be used to warn of an uneven road in those cases where traffic is required to use a carriageway with more severe undulations than those for which the "TEMPORARY ROAD SURFACE" sign variant to diagram 7010.1 would be used. See also Chapter 4 (paragraph 12.1).

The "loose chippings on road ahead" sign to diagram 7009 is used during surface dressing operations to warn of the likelihood of loose chippings on the carriageway. It must be retained in position until the danger from flying chippings has passed. This sign must be reflectorised, see Chapter 4 (paragraph 1.37). It should be accompanied by a maximum speed advised plate to diagram 513.2 indicating an advisory maximum speed of 10 or 20mph during the period that the chippings are being embedded by the traffic, see Sections D3.7 and D3.29.

The "slippery road ahead" sign to diagram 557 may be required because of the deposit on the road of mud, clay, chalk or other excavated materials (see paragraph D4.8.22). Every effort must be made to reduce this hazard to a minimum by requiring regular road washing or brushing, but the sign should be erected whenever surfaces become slippery. The provision of this sign does not absolve contractors from their duty under the Highways Act 1980. A distance over which hazard extends plate to diagram 570 may be used with the sign, see also Chapter 4 (paragraph 12.3).

The carriageway edge condition should be considered when traffic is run on the hard shoulder. Allowance should be made for the presence of kerbing, since this will have the effect of reducing the running lane width as passing traffic shies away. Fixtures, such as emergency telephones may also be closer to the edge of the hard shoulder than desirable when it is being used as a running lane. Drainage facilities on the verge can also give rise to problems if the filter medium is loose, or if there is a dished drainage channel adjacent to the edge of a trafficked lane.

The edge of the carriageway without raised kerbs should be indicated by a 100mm-wide continuous reflectorised white line to diagram 1012.1 placed approximately 200mm from the actual edge of the carriageway. Where flush kerbs are provided, the edge line should be superimposed on the kerb.

Edge protection and/or temporary widening may be needed as a temporary measure where lane widths are narrow, or where turning vehicles may cause over-run problems. If required, the designer should;

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 * locate services and discuss the need to protect them with the utilities or services provider,
 * design construction to withstand loading; and
 * review environmental concerns and reinstatement requirements.