Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/93

SIGNING PRINCIPLES The "queues likely" sign to diagram 584 is always used in combination with a supplementary plate to diagram 584.1 ("Queues likely" or "Queues likely on slip road"). The sign should be used only where there is likely to be traffic queuing upstream of the road works or temporary situations and the end of the queue could be hidden or come upon unexpectedly, e.g. hidden by a bend or where a queue may back on to a through carriageway from an exit slip road. The sign will be sited in pairs (one on each side of the carriageway or slip road) within the verge or central reservation at one mile and two miles upstream of the works, although conditions may often require different locations; see Chapter 4 for further details.

The "road narrows" signs to diagrams 516 and 517 are used to give warning that the existing carriageway width becomes restricted. The actual manner in which the carriageway width is restricted will determine which of the signs should be used. Where appropriate these signs are supplemented by a "Single file traffic" plate to diagram 518, see Chapter 4 for further details.

"Two-way traffic" signs to diagrams 521 and 522 are used to warn drivers of two-way opposing or cross traffic at situationswhere its presence might not be readily appreciated. For example, a sign to diagram 521 is used where a length of dual carriageway road under construction narrows to a single carriageway road, or where all the traffic from one carriageway of a dual carriageway road has been diverted to the other. A sign to diagram 522 is used on a one-way road to indicate that the road 521 it joins or crosses carries two-way traffic, see Chapter 4 for further details. 92