Traffic Signs Manual/Chapter 5/2009/5

5DOUBLE WHITE LINES

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GENERAL

5.1 Double white lines (see figure 5-1) are used to prohibit overtaking where visibility is restricted. Drivers may cross the line nearer to them when it is broken, but not when it is continuous. The legal requirements conveyed by the markings are specified in regulation 26(2) of the Traffic Signs Regulations and General Directions 2002 as follows:

(a)no vehicle shall stop on any length of road along which the marking has been placed at any point between the ends of the marking and

(b)every vehicle proceeding on any length of road along which the marking has been so placed that, as viewed in the direction of travel of the vehicle, a continuous line is on the left of a broken line or of another continuous line, shall be so driven as to keep the first-mentioned continuous line on the right hand or off side of the vehicle.

Exceptions are set out in regulations 26(4), 26(5) and 26(6), which list the circumstances in which vehicles are permitted to stop on a road marked with double white lines and the occasions when vehicles may cross a continuous line. The restriction on stopping in (a) above applies whether the line closest to the vehicle is continuous or broken. However, on a road with more than one traffic lane in each direction the stopping restriction does not apply. A separate traffic regulation order would therefore be necessary to prohibit waiting or loading on, for example, an urban four-lane road (see para 5.26).

5.2 Each direction of travel is marked separately according to the degree of visibility in that direction. The necessary standard of visibility is governed by the speed of vehicles on the road; surveys carried out in the summer and winter months may produce differing visibility as a result of foliage growth. Where visibility is just above the minimum standard, but overtaking may nevertheless present a danger, the warning line to diagram 1004 or 1004.1 should be used (see para 4.4). A "no overtaking" order may be imposed (see Chapter 3), but this is likely to be necessary only in very exceptional circumstances.

5.3 A continuous length of double white lines, with any number of changes between continuous and broken lines in either direction, comprises a system. A double white line scheme may comprise any number of separate systems, interrupted by other types of marking (e.g. centre lines or warning lines).

5.4 Having regard to the road width required by buses and goods vehicles, particularly on bends, double line markings should not normally be used where the carriageway is less than 6.1 m wide; a warning line should be used instead. However, an exception may be made where the width of a road drops marginally below 6.1 m for a short distance, and the omission of double lines at places of restricted visibility within the narrow section might be misleading.

5.5 Where the forward visibility is less than the desirable minimum (see para [#5.22|5.22]]) it does not automatically follow that double lines should always be installed; judgement should be exercised in deciding whether, having regard to the topographical and traffic characteristics of the route, it is reasonable to impose the restrictions or whether the warning type of marking should be used instead. Double white lines are in general well respected, but they impose arbitrary restrictions on some drivers - for example those who have a better view because they are seated higher above the road. It is important that the marking is not used where the appropriate criteria are not satisfied, otherwise it will be brought into disrepute and eventually lose the respect of drivers. Routes, including those that cross traffic authority boundaries, should be considered as a whole, in order to maintain consistent standards.

5.6 Traffic authorities should ensure that all newly-laid double line markings conform to the criteria set out in the following paragraphs. The emphasis should always be on not using double lines except where they are clearly justified on these criteria, in relation to both the length in question and as part of the route as a whole.

5.7 It is not necessary to obtain formal authorisation for the lines because discretion in deciding whether to use double lines or warning lines is left to traffic authorities. However, as contravention of the prohibitory line is an endorsable offence and is subject to the "totting-up" procedure (section 36 of the Road Traffic Act 1988) the appropriate Commissioner of Police or Chief Constable should always be consulted whenever it is proposed to install new double line markings.

5.8 Double lines should not normally be used in built-up areas, as preventing vehicles from stopping could be unduly restrictive. They might, however, be required at certain difficult positions, on three-lane hills (see para 5.27 to 5.35) or at level crossings (see paras 19.13 to 19.17).

DESCRIPTION

5.9 Double lines consist of a continuous prohibitory line accompanied either by another continuous line or by a broken permissive line to provide for the different forward visibilities in opposite directions. The broken line comprises 1 m marks with 5 m gaps. The two lines are normally spaced 175 mm apart (minimum 90 mm). The Regulations require each line to be a minimum of 100 mm wide, but 150 mm should normally be used. The overall maximum width of both lines and the gap between them must not exceed 900 mm. If a wider marking is required, version B prescribed in diagram 1013.1 (see figure 5-1) may be used, with a maximum overall width of 1200 mm. The version B marking usually tapers at each end to connect with version A, but may abut diagram 1040.2.

5.10 All double white lines must be laid in reflectorised material (regulation 31). Raised rib markings (see paras 4.39 to 4.48) must not be used. When laid in the nominal centre of the carriageway, they should be placed either symmetrically about the centre line or with the continuous line along the centre. The former arrangement would make a new installation cheaper when road studs (particularly the depressible type) are already in use. However, if the road is narrow, the latter layout could be used to give extra width to the side with the prohibitory line (see also para 5.4).

ROAD STUDS

5.11 Regulation 31(3) requires double white line systems to be fitted with road studs. Except in the circumstances detailed in para 5.12, a single row of bi-directional reflecting road studs is placed between the lines at centres between 3 m and 4.5 m. Other than at level crossings, where a spacing of 4 m should be used (see para 19.16), it is recommended that a 4.5 m spacing is adopted on all new installations. Provided they are within the above range of dimensions, it is not necessary to change existing installations to 4.5 m spacing merely to comply with this paragraph.

5.12 Where the road marking shown in version B of diagram 1013.1 is so placed that the continuous lines are more than 175 mm apart and separated by the cross-hatching shown, the studs may be fitted in opposite pairs, within the width of each of the two lines, as an alternative to a single row between them (regulation 31(4)). When they are fitted in pairs, studs should be uni-directional so that only the line of studs nearer to the driver is fitted with reflectors which can be seen by that driver.

DEFLECTION ARROWS

5.13 Direction 48 requires the provision of at least one arrow to diagram 1014 (see figure 13-6) in advance of the start of any continuous line which is on the driver's side, to warn of the approaching restriction (see also paras 5.16 and 5.18). If space permits, two arrows should normally be provided. Where a driver’s forward view of the road surface is limited, as at a crest, a third arrow may be necessary to give adequate forewarning (see figure 5-2).

5.14 Deflection arrows on the approach to a double white line system (see para 5.3) are usually positioned in the centre of the carriageway (see figure 5-2) replacing one of the centre line marks. Where the centre is marked using diagram 1040.2, the omission of a pair of edge marks and the associated diagonals will emphasise the arrow. Where arrows are required within a double white line system, they should be positioned approximately 500 mm to the right of the continuous line in order to avoid breaking the double white line pattern (see figure 5-3). All arrows on each approach must be in line with one another.

5.15 The first arrow should normally be placed a distance in advance of the start of a continuous line equivalent to one second of travel, the second arrow at a point equivalent to a further two seconds of travel, and the third, where necessary, at a point equivalent to a distance of a further three seconds of travel. The spacing for various speeds given in table 5-1 has been adjusted to fit the standard modules so that the arrow is positioned equidistantly between two warning marks.

5.16 Direction 48 provides an exemption to the requirement for deflection arrows where the continuous line is interrupted at a junction or at a refuge (see also para 7.11). They are also not required if a continuous line commences immediately after the point where a central reservation ends, or immediately after a roundabout. However, in the latter case the use of an arrow is recommended, as indicated in figure 5-4.

SPLAYED MARKINGS ON BENDS AND CRESTS

5.17 To increase the lateral separation of opposing traffic on sharp bends or crests, double continuous lines, where they are justified, may be splayed with a maximum overall width of 1200 mm (diagram 1013.1 version B); if greater widths are required, diagram 1013.4 should be used (see figures 7.5 and 7.6). It is essential that there is adequate room on each side to enable vehicles to negotiate the bend or hump without crossing the lines. The lines should be opened out at a taper no sharper than 1 in 50; the area between them must be hatched with marks of the same width as the longitudinal lines, at spacings of not more than 3 m. On a crest, the lines should attain maximum width at the point of least visibility(not always the highest point) in each direction. This hatched marking may be used only between double continuous lines, never between a continuous and a broken line.

INCLINED LINES AT REFUGES

5.18 Double lines should not be splayed where they meet a refuge. Both lines should be inclined to the driver's side of the refuge, keeping them parallel to each other so that traffic is guided safely past the refuge (see figure 5-5). Guidance on the appropriate offset between the line and the refuge can be found in para 4.23. Lines should not be continued alongside the refuge. Recommended tapers are set out in table14-1. Where a refuge interrupts a continuous line, warning arrows are not required at the recommencement of the marking after the refuge. If on the approach to a refuge the line on the driver's

Table 5-1 Location of deflection arrows

Speed limit (mph)	Length of arrow (m)	Distance of tip of arrow from the start of the unbroken line (m)
		First arrow	Second arrow	Third arrow
30	4.5	13.75	43.75	79.75
40	4.5	19.75	55.75	109.75
50	6	21.00	66.00	138.00
60	6	30.00	84.00	165.00

side is broken, it should be replaced with a continuous line between the refuge and a point V metres in advance of it (see table 5-2). This avoids inviting an unsafe overtaking manoeuvre.

ROAD JUNCTIONS

5.19 Improved visibility sometimes results in reversion to a broken line on the approach to a junction. In such cases, it is better to maintain the continuous line beyond the junction to avoid encouraging overtaking at an unsuitable point.

5.20 The Regulations permit vehicles to cross the continuous line to enter any other road or private access (regulation 26(6)). A gap in the line is not therefore necessary. However, where there is a dedicated right turn lane this should be marked out as shown in figure 7-4 and described in para 7.11. The Directions do not require deflection arrows at the recommencement of the double line either side of the junction.

5.21 The use of double white lines in conjunction with a right turn lane on a road with a climbing lane is dealt with in para 7.12.

VISIBILITY DISTANCE

5.22 Visibility distance is defined as the maximum distance at which an object 1.05 m above the carriageway can be seen by an observer at the same height, taking account of vertical as well as horizontal curvature. In table 5-2, for each speed interval, V is the desirable minimum visibility distance and W is the warning line visibility distance as measured between points on the centre of the carriageway. Warning lines are laid where overtaking is potentially hazardous, but visibility is not so restricted that overtaking needs to be prohibited (see paras 4.12 to 4.26).

Table 5-2 Visibility distance

85 percentile speed (mph)	Desirable minimum visibility distance V (m)	Warning line visibility distance W (m)
Up to 30	75	115
31 to 40	95	160
41 to 50	120	195
51 to 60	150	240
Over 60	175	275

DESIGN PROCEDURE FOR TWO-LANE ROADS

5.23 Double white line systems (see para 5.3) should not be designed entirely on the basis of plans and sight distance data. A site visit should always be made, and other relevant information such as the accident record taken into account. The complete scheme, with all adjustments, deflection arrows and associated markings should then be designed on a large-scale plan before any markings are laid on the road. The visibility distances used to determine the double line scheme should be based on actual 85th percentile measured speeds where this is higher than the speed limit. For measured 85th percentile speeds of 30 mph or less (see table 5-2) the visibility distances for 30 mph should be used.

Step 1	Determine traffic speeds along the sectionfor each direction of travel. From table 5-2,find the desirable minimum visibility V for each part of the section, in each direction.
Step 2	For one direction of travel, mark each of the points where desirable minimum visibility distance V is lost, and where it is regained. Each of these pairs of points can now be joined by a continuous white line to create a series of line segments, except where such a segment would be shorter than V / 4, and would be separated from its preceding and succeeding segments by at least the relevant V (note 1(a) below); such short isolated segments should not be marked as continuous unless there is very good justification for retaining them.
Step 3	On the exit from a left hand bend, the continuous line should be extended until the warning line visibility distance W is attained, or the road ceases to curve to the left, whichever results in the shorter line.
Step 4	Gaps shorter than the relevant V (note 1(a)) between continuous line segments should be closed by extending the continuous line.
Step 5	Repeat Steps 2, 3 and 4 for the other direction of travel.
Step 6	On the plan, mark broken lines alongside remaining single continuous lines, on the appropriate side (i.e. on the side for the direction of travel in which a driver has visibility better than V). This will result in the creation of a number of lengths of double white lines.
Step 7	If the gap between two lengths of double white line systems is shorter than half the relevant V value (notes 1(b) and 2 below), the systems should be extended, without a change in pattern, to fill the gap. Normally the systems would meet in the middle of the gap, but the designer should adjust the point of meeting to minimise loss of length from overtaking sections (note 3), or to avoid the release of traffic at an unsuitable point.
Step 8	If this joining of systems results in a length of broken line within the resulting system (i.e. not at one end) that is shorter than the relevant V (note 1(a)), then that length of broken line should be replaced by a continuous line.
Step 9	If the gap between two systems is greater than half the relevant V (note 1(b)), but less than the relevant W (note 4), warning lines should be laid in the gap between the systems.
Step 10	If traffic leaving a length of double white lines is subject to a continuous line that extends beyond the point where the continuous line for traffic in the other direction starts, and it seems that this might cause confusion, the inbound continuous line may be started sooner, at the designer's discretion.
NOTES:
1(a)	In a particular direction, the relevant V value for a gap between two continuous lines is taken to be the same as that used to determine the start of the continuous line after the gap.
(b)	When considering the gap between two systems, if the application of note 1(a) results in a different V in each direction, the greater value should be used.
2	V / 2 is used here in preference to V to avoid excessive lengths of unnecessary continuous line. Overtaking lengths less than V that might arise are closed later, at Step 8.
3	When adjusting the meeting point of systems, the designer should take account of the availability of other (perhaps safer) overtaking opportunities in the vicinity.
4	The relevant W value at any point is taken to be that for the speed corresponding to the relevant V value at that point, defined under 1(a) and 1(b) above.

5.24 The above procedure achieves the following:

(i) the minimum length for an overtaking stretch is V,

(ii) the minimum length for a broken line element within a system is V, and

(iii) the minimum length for a stretch of warning line between two systems is V / 2.

This minimises both frequent changes of pattern and the length of continuous line put down at places where visibility is adequate.

THREE-LANE ROADS

5.25 The use of offset double lines on alternate sections of three-lane roads (other than three-lane hills, see paras 5.27 to 5.32) to facilitate overtaking in the centre lane is not recommended. Drivers will not respect restrictions which have no apparent justification. Carriageways 10 m or more in width may be marked with a centre of carriageway marking in accordance with table 4-3, or with double white lines if there are four or more lanes (see para 5.26).

FOUR-LANE ROADS

5.26 On single carriageway roads with two or more lanes in each direction, the centre may be marked with a double continuous line irrespective of visibility. This should eliminate the possibility of a vehicle overtaking in one direction being confronted by an opposing vehicle which is "double overtaking" bycrossing the centre line.

THREE-LANE HILLS

5.27 A three-lane hill is intended to provide two lanes for ascending traffic so that faster-moving vehicles may overtake slower ones in safety. The downhill traffic may be fully confined to one lane, or partially confined if overtaking is permitted. The left hand uphill lane should be a continuation of the nearside lane, with the widening to the right, so that slower vehicles do not have to change lanes at either end. The procedure for marking three-lane hills, set out below, is designed to result in markings that allow downhill overtaking only at those locations where visibility is extensive in both directions.

5.28 A three-lane hill is marked with a lane line (diagram 1005 or 1005.1) separating the two uphill lanes, and a double white line separating them from the downhill lane (see figure 5-6). Where the carriageway width is the standard 10 m (excluding any edge strips) it should be marked so that the uphill climbing lane is 3.2 m wide and the other lanes each 3.4 m wide. For further details see TD 9 / 93 in the Design Manual for Roads and Bridges (Volume 6).

5.29 The double white line will always feature a continuous line on the side of the uphill traffic. On the downhill side, where certain criteria are met, the line may be broken to permit overtaking. These criteria are determined as follows:

(i) establish the 85th percentile traffic speed for the downhill direction, and determine from table 5-2 the appropriate warning line visibility distance W,

(ii) measure downhill visibility with the observer on the proposed alignment of the double white line, but with two targets, one on the proposed alignment, and the other on the lane line separating the two uphill lanes. The visibility criteria are satisfied only when both targets are simultaneously visible at a distance W from the observer, and when no part of the sight line to the target on the lane line at any point passes over the inside uphill lane (where it could be obscured by an uphill vehicle). This ensures adequate forward vision for a driver in either direction who intends using the centre lane to overtake,

(iii) a broken line is installed for downhilltraffic only where the criteria in Step 2 of para 5.23 are satisfied, and only if it can be installed for a minimum length W. Otherwise a continuous line is used toprohibit downhill overtaking.

To avoid frequent changes of pattern on long hills, or for safety reasons, the designer may on occasion use a downhill continuous line even when the visibility criteria for a broken line in Step 2 are satisfied, although the use of a prohibitory line on long straight sections should be avoided if possible.

5.30 The marking at the commencement of the climbing lane is designed to encourage uphill drivers to keep to the near side lane unless overtaking. In order to avoid a potential conflict at this point between uphill and downhill overtaking traffic, a length of double continuous line should be provided for a length equal to W in table 5-2 for the speed of the uphill traffic. This ensures that any downhill overtaking vehicle will be returned to the near side lane before coming into conflict with an uphill vehicle beginning an overtaking manoeuvre at the start of the climbing lane (see figure 5-6). In addition, the double white line may be extended to divide opposing traffic over the taper in order to prevent overtaking by downhill traffic. However, if visibility over this length is good, then observance may be poor and a warning line might be more effective.

5.31 This procedure will still allow downhill overtaking on long straight, or nearly straight, hills. It will restrict it elsewhere, particularly in those cases where visibility is poor for an uphill inside lane vehicle trying to pull out from behind a large vehicle.

5.32 The alignment at the end of a climbing lane should place the onus on the overtaking driver to rejoin the inside lane. Care should be taken to ensure that the return to a single lane does not occur where junctions or sharp curves may cause problems. See figure 5-6 for the layout of markings at the top and bottom of a climbing lane. Signs to diagram 517 should also be used (see Chapter 4, para 4.3).

LAYOUT AT SAG CURVES

5.33 Where there are climbing lanes on both sides of a sag curve, a conventional two-lane road layout may be used to link them, provided this is at least 500 m in length between tapers. For shorter lengths, the intervening carriageway should be maintained at 10 m wide and the climbing lanes extended

downhill until they meet, using a road marking to diagram 1013.1 version B (see figure 5-7). The taper in the version B marking (see figure 5-1) should not be sharper than 1 in 50.

LAYOUT AT CRESTS

5.34 Where there are climbing lanes on both sides of the hill and the road has been widened on the crest to 13.2 m, as indicated in TD 9 / 93 (Amendment No.1) in Volume 6 of the Design Manual for Roads and Bridges (see para 1.4) then:

(i) if the length of 13.2 m wide carriageway (including any hatched area) between the tapers is 500 m or more, a conventional layout should be used between the tapers,

(ii) if the length of 13.2 m wide carriageway between the tapers is less than 500 m, the climbing lanes should overlap as shown in figure 5-8. In this case the distance between the tapers (i.e. the length of 13.2 m carriageway including hatching) should not be less than 200 m.

5.35 If the carriageway over the crest remains unchanged in width at 10 m, the marking layout shown in figure 5-9 should be adopted.

LEVEL CROSSINGS

5.36 Double white lines are used at some level crossings even when the conditions do not meet the visibility criteria in table 5-2 (see paras 19.9 to 19.17 for details). Markings should be installed at level crossings only after consultation with HM Railway Inspectorate.

This work has been mirrored or sourced from material provided on the UK Government website at https://www.gov.uk/government/publications/traffic-signs-manual, which states material is available under the terms of the Open Government License unless indicated otherwise. (Crown copyright acknowledged.)

This is NOT an official transcription, and should NOT be considered in any way a controlled copy of the work in question.

This document no longer necessarily represents current practice, as it relates to an earlier version of the regulations (TSGRD 2002 as amended at publication date) rather than the current TSRGD 2016 regulations. It should not be used for actual design or operational use without consulting a more recent edition.

This version was transcribed in May 2015, from a 2009 impression.