Department of Transport

“ It is important therefore that sight lines are properly maintained so that the intended warning is not compromised. Care in siting can minimise future problems of obscuration. Sight lines should not cross private land as it will be difficult to control the growth of vegetation or the placement of other obstructions. It is equally important that warning signs should not be placed where they will obstruct the view of other signs. e.g. advance direction signs. Such problems might be avoided by siting the sign further from the hazard, or on the right hand side of the road. ”

“ This is to ensure that drivers have the necessary time to respond to the warning. Appendix A sets out recommendations for the distance from the hazard at which a sign should be sited. If it is impracticable to place a sign within about 10% of the recommended distance, it should be sited further upstream of the hazard at the nearest practicable point. It may be appropriate to supplement it with a distance plate to diagram 572 (see section 18) . A sign should not normally be sited more than 10% closer than the recommended distance, as this would be unlikely to provide sufficient warning. ”

“ ILLUMINATION
1.35 On unlit roads, reflectorisation generally produces an adequate level of sign luminance in the illumination from a vehicle’s headlamps. In areas of street lighting, however, much higher levels of luminance are required to ensure that signs are always adequately conspicuous. Reflectorised materials cannot guarantee luminance levels comparable to those provided by direct lighting. Modern microprismatic materials achieve high luminances for many drivers in defined situations, but not for all drivers in all circumstances. ”

“ A backing board must not itself be provided with a border, nor give the impression of being an additional border. Where it seems that a sign is not being noticed by drivers, it should be checked to ensure that it is well-sited, not obscured by foliage or other obstructions, and is of the appropriate size and in good condition. Only then should the use of a yellow backing board be considered.
1.33 A yellow backing board may be reflectorised to increase its conspicuity at night. ”

“ The problem can occur even when there is more than one lane. At times of light traffic flow, a vehicle being driven in the left hand lane at 70 mph might close unexpectedly rapidly on a slow-moving lorry, or on a queue of vehicles waiting to pass it. ”

“ Dual carriageway situations are dealt with in para 4.6. Signs will not normally be needed if the narrowing does not result in the loss of a lane and involves a taper no more severe than indicated in table 4-1. However, signs should be provided regardless of the rate of taper where a lane is lost on a single carriageway road or where the reduction in width is so great that the centre line marking has to be omitted (see also para 4.4) . The "REDUCE SPEED NOW" plate (diagram 511) should be used if a significant speed reduction is advisable. ”

“ On two-lane carriageways subject to a 30 mph speed limit, a single sign mounted on the side of the road on which the lane is to be lost may be adequate, although the possibility of obscuration by parked vehicles should be considered. Also all-purpose dual three-lane carriageway roads subject to a 70 mph speed limit. ”

“ This problem in dealing with information overload increases with age, so that older drivers suffer disproportionately. Generally, therefore, not more than two signs should be mounted on one post. When a sign is accompanied by a supplementary plate, the combination of sign and plate should be regarded as one sign for this purpose. Exceptionally, three signs may be mounted on one post provided none requires a supplementary plate.
1.28 Warning signs should not be mounted on the same post as a STOP or GIVE WAY or terminal speed limit sign, nor mounted on a traffic signal post. ”

“ Signs located where they are subject to heavy soiling from passing traffic, or algae growth (a common problem with signs beneath tree canopies) will need more frequent cleaning. Neglect reduces the external contrast between the sign and its surroundings, making it less likely to be noticed by drivers. It also reduces the internal contrast between legend and sign background, making the sign more difficult to read. Moreover, it seriously reduces light transmission through the retroreflective medium. Dirty signs will be far less effective at night. Older drivers are particularly disadvantaged ”

“ For the 600mm and 750 mm size triangles, the smaller x-height, where more than one is shown, is appropriate if the 85th percentile speed is 20 mph or less. Where a 50 mm x-height is marked with an asterisk, this is the standard size for 85th percentile speeds up to 30 mph. For the 1200 mm size triangle, the larger x-height, where more than one is shown, should be used on dual carriageway roads where the national speed limit applies or on single carriageway roads where greater emphasis is required. ”

“ The direction of the arrow may be reversed
10.15 A cattle grid on a public road should always be preceded by the cattle grid warning sign to diagram 552, as it might otherwise catch drivers unawares. Grids are especially hazardous for two-wheeled traffic. Signs should normally be sited at the standard distances set out in Appendix A. The plate to diagram 553 indicating the direction of the by-pass for horse-drawn vehicles or accompanied animals can accompany the sign it the entrance to the by-pass is reasonably close to the grid. ”

“ The alternative route may be varied as appropriate and may include a reference to a motorway junction. A diversion route symbol may be added. Details of the permitted variants are shown in the table below the diagram in the Regulations
7.13 In order to reduce the risk of the driver of an overheight vehicle being confronted with an impassable bridge, it is important that properly planned diversion route signing is provided, certainly where a structure has a history of repeated strikes. In such a case, it is not sufficient to rely on warning signs alone. ”

“ Lights are not recommended unless the driver’s field of clear visibility is less than the distance shown, or the traffic flow exceeds 10,000 vehicles per day on roads where the 85th percentile speed exceeds 30 mph. ”

“ Its use should be restricted to sites where numbers of slow-moving pedestrians are likely to cross a road other than at a Zebra or signalled crossing. This might be near sheltered housing or nursing homes, where drivers need to be reminded that a pedestrian in the road ahead might be frail or blind and need more time to cross than an able-bodied person would. ”

“ BRIDGE PARAPET OR OTHER OBSTRUCTION
528.1 End of bridge parapet or other obstruction
7.2 Signs to diagram 528.1 should be used where a bridge parapet, abutment or other obstruction is immediately adjacent to, or encroaches onto, the carriageway. This includes any parapet or abutment on the off side where it would be a hazard to drivers overtaking or passing a temporary obstruction on the near side. In addition to the risk to passing road traffic, damage to a parapet can also result in considerable danger to rail traffic. ”

“ At a crossing where the safe height is below 16’-6” (5.03 m) , the height shown on the signs should be at least 1'-9" (530 mm) or 1’-3” (380 mm) respectively below the conductor and a load gauge to diagram 781 erected at the safe height. In calculating the safe height, allowance should be made for the effect of the vertical profile of the carriageway on a road vehicle and its load. While the Regulations permit the omission of the height indication in metric units, this is inadvisable. Table 21-1 indicates the heights to be shown on the signs for different cable heights. ”

“ Where queues on the slip road effectively shorten the deceleration length available, but do not usually extend onto the main through carriageway, the variant "Queues likely on slip road" should be used. Care should be taken to ensure that the assembly does not obstruct the driver's view of existing signs. ”

“ Their frequent use to warn of conditions which are readily apparent tends to bring them into disrepute and detracts from their effectiveness. Unjustified signing should not be used at individual locations simply in response to complaints from the public. Care should be taken to ensure that a route is treated consistently, especially where it crosses the boundary between two traffic authorities. ”

“ Details are shown on the working drawings (see para 1.8) .
"with passing places" may be varied to "Use passing places to permit overtaking" or to "No passing places for" and a distance expressed in yards or miles as appropriate
4.5 If a road is wide enough for only one line of vehicles but there are passing places marked with diagram 822 "PASSING PLACE", diagram 821 "Single track road with passing places" should be used at each end of the single track section. The legend "with passing places" may be varied to "No passing places for" and a distance in yards or miles. ”

“ The height indicated on the warning signs, determined in accordance with paras 7.8 to 7.12, should be the lowest headroom between the chord limits. On a narrow bridge where the headroom decreases rapidly away from the centre, a 3 metre chord marking is appropriate. On a wide bridge with only a gradual reduction in headroom it might be possible to increase the chord width to 6 metres or more without excessively restricting the signed height, thus maintaining two-way operation for all vehicles that can pass under the bridge. ”

“ For further guidance on sign siting, see paras 1.20 and 1.21. Where a range is quoted for siting distance in column 4, progressively larger figures should be used for 85th percentile speeds towards the higher end of the speed range, to compensate for the greater braking distance. Braking distance will also be affected by gradients, and siting distances may need to be increased on steep hills, eg an increase of 50% might be made for a 10% descent. ”

“ Nor is a warning sign normally required when a stack-type advance direction sign is used, except where the layout will not otherwise be apparent, eg at a staggered crossroads Signs are required at junctions controlled by traffic signals only in the circumstances described in para 8.3. Exceptionally, warning signs may be provided in addition to advance direction signs where visibility is so poor that drivers are unable to obtain an adequate advance view of the junction or the directional signs associated with it. ”

“ The smallest size of the sign to diagram 785.1 (25 mm x-height) is intended to be read only by a driver having alighted. A larger size will be required if it is necessary for the sign to be read from a moving vehicle. As non-compliance with the sign to diagram 784.1 could result in an accident or expose a driver to prosecution, it is essential that this group of signs is appropriately sized and properly maintained.
May be used with diagram 782, 783, 784. 7, 787, 788 or 7 028.3. "AT CROSSING" may be omitted. ”

“ Account should always be taken of the potential environmental impact of tall and cluttered arrays of signs.
1.31 It should also be borne in mind that high-mounted signs may receive little light from vehicle headlamps, particularly on dipped beam. Where such signs are not directly lit but rely on reflectorisation to be seen at night, they are likely to be less legible (see also para 1.36) . ”

“ The gauge is intended for use with power cables and not at low bridges over public highways, where speeds are likely to be higher and drivers less able to respond to the sound of the bells in time, or even to hear them at all from inside closed cabs.
21.12 The load gauge must be mounted on two posts coloured black and white in alternate horizontal bands each band being less than 250 mm nor more than 335 mm deep (Direction 43.) ”

“ The distance may be varied (see Appendix C)
6.3 On very steep or long hills where additional warning is considered necessary, the sign may be repeated as appropriate, supplemented with the "Low gear" plates shown in diagrams 525, 526 or 527. These plates must not be used alone. 6.4 The circumstances justifying the additional plates cannot be stated precisely. Traffic authorities, after consulting the police, will have to assess the need to advise drivers to engage a lower gear and gauge the likelihood of this instruction being respected. ”

“ The metric dimension (but not the imperial) may be omitted from diagrams 780A, 780.1A and 780.2A. The maximum distance permitted on diagram 818.1 is 2 miles. Permitted variant 1 applies to the height restriction. When permitted variant 10 applies, the word "ahead" is omitted. Permitted variant 1 applies to the height restriction. Permitted variant 6 applies when a distance is added. Permitted variant 1 applies to the available headroom. Permitted variant 6 applies when a distance is added. ”

“ In practice it will not be necessary to use them at the very smallest roundabouts, provided the speed limit is 30 mph or less, the diagram 606 arrow being sufficient. They should normally be used whenever the diameter of the central island exceeds 8 metres.
3.21 It the sign is used in the central reserve or on the off side of a slip road on the immediate approach to a roundabout, it should not be sited where it would impair the driver’s view of circulating trafic. ”