# Traffic Signs Manual/Chapter 5/2009/4

CENTRE LINES
4.1 The 1994 Regulations introduced new markings intended for use as centre lines separating opposing flows of traffic on single carriageway roads. These are illustrated in figure 4-1 and the dimensions and recommended applications are shown in table 4-1. Diagram 1008 is used where the speed limit is 40mph or less, and 1008.1 where the speed limit is more than 40 mph.
Table 4-1 Centre line on single carriageway roads :
| Diag No. | Speedlimit(mph) | Mark(m) | Gap(m) | Width(mm) | Spacing of studs(if used) (m) | Description |
| 1008 | 40 or less | 2 | 4 | 100 | 12 | Two-lane roads, not less than 5.5 m in width |
| 1008 | 40 or less | 2 | 4 | 150 | 6 | Two-lane roads 10 m or more in width (or three lanes marked as two in one direction and one in the other) Four lanes or more (see para 4.3) |
| 1008.1 | Over 40 | 3 | 6 | 100 | 18 | Two-lane roads, not less than 5.5 m in width |
| 1008.1 | Over 40 | 3 | 6 | 150 | 9 | Two-lane roads 10 m or more in width (or three lanes marked as two in one direction and one in the other) Four lanes or more (see para 4.3) |
4.2 All new installations and reinstatements must use diagrams 1008 and 1008.1 for centre line markings (where warning lines and double line systems are not appropriate) in place of old markings to diagram 1005.
4.3 The marking should be used only on single carriageway roads. Where the road comprises one lane in each direction, the 100 mm wide marking will normally be sufficient. On four-lane roads, three-lane marked as two in one direction and one in the other, or two-lane 10m wide, the 150mm marking should be used. Any lane lines should be 100 mm wide (see paras 4.7 to 4.11). The centre line should never be narrower than the lane line (see para 4.10). It may be ​replaced by the warning line (see paras 4.12 to 4.26) where appropriate. When there are two or more lanes in each direction, consideration might be given to double white lines (see section 5).
4.4 Where forward visibility is restricted (see para #4.16) or on the approach to some other hazard (e.g. a roundabout or other junction), the centre line marking should be replaced with warning lines to diagrams 1004 or 1004.1 (see figure 4-3). These are the inverse of the mark/ gap dimensions for the centre line and therefore maintain the same module (see table 4-3 for the minimum number of marks).
4.5 On two or four lane roads the marking should normally be laid in the geometric centre. It can however be laid off-centre to allow parking along one side. Where it is necessary to change the position of lines in relation to the centre of the road, the deflection should be smooth and made at the inclinations specified in table 14-1.
4.6 On rural roads below 5.5 m in width, over-running of the carriageway edge can occur if centreline markings are provided, causing maintenance problems. Drivers might also expect a road marked with a centre line to be wide enough for opposing lanes of traffic to pass. In these circumstances the centre line should be omitted, but it would be helpful if edge of carriageway markings are then used.
LANE LINES
4.7 Lane lines (see figure 4-2) ensure that available carriageway space is used to its maximum capacity. In-helping vehicles to maintain a consistent lateral position, they also offer safety benefits and should be used wherever practicable.
Table 4-2 Lane lines :
| Diagram No. | Speed limit (mph) | Mark (m) | Gap (m) | Width (mm) | Spacing of studs (if used) (m) |
| 1005 | 40 or less | 1 | 5 | 100 (150) | 12 |
| 1005.1 | Over 40 | 2 | 7 | 100 (150) | 18 |
4.8 The marking is intended for dividing the carriageway into lanes where traffic on either side of the line travels in the same direction, and not for separating opposing flows of traffic. Details are set out in table 4-2.
4.9 Lane lines on the approach to Give Way and Stop markings, including roundabouts and traffic signals, should change to warning lines in accordance with table 4-3 and para 4.24.
​4.10 On single carriageway roads with more than two lanes, the centre line should normally be of a greater width than the lane lines. This is particularly important when the warning module is used for both, making it more difficult to determine which line divides the opposing traffic streams.
4.11 On 70 mph dual carriageway all-purpose roads and on motorways, the wider (150mm) marking should be used as this increases its visibility distance. It is also likely to be of benefit on concrete roads, even with a lower speed limit, helping to compensate for the reduced contrast.
WARNING LINES
4.12 Warning lines are detailed in figure 4-3 and table 4-3. They are used:
(i) as centre lines at bends and crests, and on multi-lane roads (see paras 4.16 to 4.18),
(ii) as centre lines where it is necessary to highlight the presence of a road junction, central refuge or other hazard (see paras 4.19 to 4.23),
(iii) approaching or through junctions (see para 4.24 and sections 7, 8, 9 and 10),
(iv) to mark the boundary of advisory cycle lanes (see paras 16.9 and 16.10), and
(v) over road humps (see para 21.10).
4.13 Warning lines are always single; they must never be used as part of a double line installation, and must not be formed of raised rib markings (see paras 4.39 to 4.48).
4.14 Two patterns of warning line are prescribed,each having alternative widths of 100 or 150 mm. The wider line is visible at a greater distance, and should be used where this might be beneficial, e.g. at particularly hazardous sites (see also para 4.10). The two standard modules are 6 metres and 9 metres in length (the combination of one mark and one gap) depending on the speed limit. Table 4-3 sets out appropriate arrangements for various road layouts and speed limits.
fig4.3
4.15 Overuse of the marking should be avoided. Its use where it is not justified will devalue its effect. Particular care should be taken in urban areas where there might be a temptation to use it extensively.
4.16 Warning lines are used in place of centre lines where forward visibility is less than the warning line visibility distance W indicated in table 4-4. This is based on the visibility necessary for safe overtaking on a two-way carriageway (see para 5.22 for the definition of visibility distance). For intermediate speeds, the appropriate visibility distance should be taken as the higher figure between the steps shown, e.g. for an 85th percentile speed of 45 mph, warning lines are justified when visibility is between 120 and 195 m. Where the visibility distance is less than the desirable minimum V, a double white line system should be considered (see section 5).
​4.17 Where warning lines are used to separate opposing flows of traffic on single carriageway roads, they should normally be laid in the geometric centre of the carriageway (see also para 4.5).
4.18 On four-lane roads the 150 mm wide warning line may be used to separate opposing traffic, although consideration might be given to the use of double white lines (see section 5). On three-lane roads marked with two lanes in one direction and one in the other, the 150 mm wide line should be used, together with 100 mm wide lane lines. The lane line should never be wider than the warning line.
4.19 Warning lines may be used to highlight the presence of a road junction (see section 7 for further guidance) and to mark the approach to central refuges or other hazards, (see para 4.23), except where these are within a double line section.
4.20 On straight sections of road, warning lines on the priority route would normally be appropriate when the average traffic volume from the side road exceeds about 100 vehicles per hour. However, warning lines will be justified at lower traffic volumes where visibility of the junction is impaired.
Table 4-3 Warning lines :
| Diag No. | Speed limit(mph) | Mark (m) | Gap m) | Width (mm) | Spacing of studs (if used) (m) | Minimum number of marks on each approach | Minimum number of marks on each approach | Minimum number of marks on each approach | Purpose |
| Purpose |||
| Diag No. | Speed limit(mph) | Mark (m) | Gap m) | Width (mm) | Spacing of studs (if used) (m) | 30 | 40 | Over 40 | Purpose |
| 1004 | 40 or less | 4 | 2 | 100 | 6 | 5 | 7 | – | Central warning line on two-lane roads less than 10 m wide |
| 1004.1 | Over40 | 6 | 3 | 100 | 9 | – | – | 7 | Central warning line on two-lane roads less than 10 m wide |
| 1004 | 40 or less | 4 | 2 | 150 | 6 | 5 | 7 | – | Central warning line on two-laneroads 10 m or more wide |
| 1004.1 | Over 40 | 6 | 3 | 100 | 9 | – | – | 7 | Central warning line on two-laneroads 10 m or more wide |
| 1004 | 40 or less | 4 | 2 | 150 | 6 | 7 | 10 | – | Central warning line on four or six-lane single carriageway roads |
| 1004.1 | Over 40 | 6 | 3 | 150 | 9 | – | – | 10 | Central warning line on four or six-lane single carriageway roads |
| 1004 | 40 or less | 4 | 2 | 100 | 6 | 5 | 7 | – | Lane line on all roads on approach to roundabouts or signal controlled junctions, and the minor road approaching a priority junction |
| | 50 | 6 | 3 | 100 | 9 | – | – | 7 | Lane line on all roads on approach to roundabouts or signal controlled junctions, and the minor road approaching a priority junction |
| 1004.1 | 60 | 6 | 3 | 100 | 9 | – | – | 7 | Lane line on all roads on approach to roundabouts or signal controlled junctions, and the minor road approaching a priority junction |
| | 70 | 6 | 3 | 150 | 9 | – | – | 7 | Lane line on all roads on approach to roundabouts or signal controlled junctions, and the minor road approaching a priority junction |
NOTE: These markings may also be used to delineate an advisory cycle lane (see para 16.9).
Table 4-4 Visibility distances :
| 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 |
4.21 The minor road should be marked with at leastthe minimum number of marks shown in table 4-3. On narrow two-way minor roads where the Give Way or Stop marking is extended over the whole width(see para 3.3), a warning line is not provided.
4.22 If the minor road is a one-way street, a warning line on the major road will normally be needed only if the direction of flow is towards the major road. The principal purpose of the marking is to warn drivers of the risk of unseen vehicles emerging.
4.23 A warning line approaching a refuge, central reservation etc. should be inclined for its full length(see table 4-3 for the minimum number of marks), terminating in a position offset 300 mm from the edge of the refuge (see figure4-4). This may be reduced when the speed limit is 40 mph or less and there is limited width between the island and the near side kerb, but should preferably not be less than 150 mm. Kerb faces will not normally exceed 75mm, because of the risk of loss of control if struck by a vehicle. Where unusually high kerbs are used, the 300 mm clearance should always be provided. When the length of taper required to comply with table 14-1 needs more marks than the minimum specified in table 4-3, the number of marks should be increased sufficiently to ensure that the entire taper length uses the warning module. Guidance on the use of hatched markings for additional emphasis is given in paras 4.49 to 4.51 and further advice on the treatment of refuges in section 14.
4.24 On dual carriageway roads, or single carriageway roads with two or more lanes in one direction, warning lines should be used in place of lane lines on the immediate approach to signal controlled junctions or roundabouts. Where additional lanes are introduced on the immediate approach to a roundabout it might not be possible to provide the minimum number of marks. In such cases as many marks as possible should be used without reducing any lane width below 2 m at the start of the taper (see para 8.3). The detailed arrangements for marking roundabouts and signal controlled junctions are described in sections 8 and 9 respectively.
4.25 The number of marks recommended in table 4-3 is the minimum on each approach, although this is not always possible on minor roads. The number of marks should be extended wherever justified by road or traffic conditions; the marking can with benefit be extended to start at the location of the accompanying warning sign. Figure 4-5 indicates
4.26 Where there are two features that would justify warning lines (e.g. two junctions, or a junction followed by a bend), then a short length of standard centre line between two warning lines can help to highlight the separate hazards, even if this results in fewer than the minimum number of marks being provided for the second hazard.
EDGE OF CARRIAGEWAY LINES
4.27 The following types are prescribed:
(i) diagram 1009 (see figure 4-6, para 4.28 and table 4-5),
(ii) diagram 1010 (see figure 4-7, paras 4.29 and 4.30 and table 4-5),
(iii) diagram 1012.1 (see figure 4-8, paras 4.31 to 4.38 and table 4-5 and, when used at level crossings, para 19.9), and
(iv)diagrams 1012.2 and 1012.3 (see paras 4.39 to 4.48, table 4-5 and figure 4-9).
4.28 Diagram 1009 should be used to extend the transverse Give Way and Stop line markings across the entry half width of the minor road as illustrated in figures 3-1 and 3-2. It is used across the full width if the minor road is one-way away from the junction. The normal width of the line is 100 mm but when it isused in conjunction with a continuous edge line, the width should be varied to match. The marking maybe used as an alternative to diagram 1010 across private driveways where the larger marking would be impracticable, e.g. because of the narrowness of the entrance. Where the width of the minor road is such that Give Way or Stop lines would be less than 2.75 m long, these should be extended across the whole width of the road (see para 3.3). The use of diagram 1009 at the start of cycle lanes is dealt with in paras 16.6, 16.8 and 16.10.
4.30 Further guidance on the use of diagram 1010 can be found in:
section 10 for grade separated junctions, section 17 for bus lanes, section 18 for tram markings, and
4.31 Diagram 1012.1 is intended for general use to delineate the edge of carriageway, particularly on unlit classified roads and those not having clearly defined raised kerbs. It should also normally be used on all-purpose roads with hard shoulders or hardstrips, on motorways, unless profiled edge lines are used (see paras 4.39 to 4.48) and to delineate footways at level crossings (see para 19.9).
4.32 Trials have shown that edge markings have merit as a safety measure despite their efficiency sometimes being impaired by dirt because of their location near the edge of the carriageway. They can also help to protect verges on narrow rural roads.
4.33 The marking should be laid with a gap of approximately 225 mm to the near side edge of the carriageway. The continuous line should not be carried across the mouths of side roads, acceleration or deceleration splays, gaps in the central reservation or lay-bys, where lines to diagrams 1009 or 1010 should be used.
4.34 Where the carriageway is less than 5.5 m in width, the centre line should be omitted (seepara4.6) but edge lines, where used, continued. Where edge lines are not already in use, their introduction over the length where the centre line is interrupted will help draw attention to the hazard.
Table 4-5 Edge of carriageway markings :
| Diag No. | Mark (m) | Gap (m) | Width (mm) | Width (mm) | Width (mm) | Spacing of studs (if used) (m) | Description |
| Description |||
| Diag No. | Mark (m) | Gap (m) | 40 or less | 50 or 60 | 70 | Spacing of studs (if used) (m) | Description |
| 1009 | 600 | 300 | See para 4.28 | See para 4.28 | See para 4.28 | Not used | Edge of carriageway at a road junction when a Give Way or Stop marking is used, or field entrance or exit from a private drive onto a public road |
| 1009 | 300 | 150 | 100 | 100 | 100 | Not used | Edge of carriageway at a junction of a cycle track and another road |
| 1009 | 600 | 300 | 150 | 200 | 200 | Not used | Diagonal marking at the start of a cyclelane (see also section 16) |
| 1010 | 1000 | 1000 | 100 | 150 | 200 | 8 | Edge of carriageway at a road junction when a Give Way or Stop marking is not used, or exit from a private drive onto a public road, or at a lay-by |
| 1010 | 1000 | 1000 | 250 or 300 | 250 or 300 | 250 or 300 | Not used | Start of a bus lane or interruption of a with-flow lane at a left turn (see figure 17-1). The line width will match the associated marking to diagram 1049 |
| 1010 | 1000 | 1000 | 100 | 150 | 200 | Not used | To show the most suitable path for vehicles through an arch bridge |
| 1010 | 1000 | 1000 | 100 | 150 | 200 | Not used | Edge of part of a carriageway used by tramcars |
| 1010 | 1000 | 1000 | 100 | 150 | 200 | See para 10.11 | Division between the main carriageway and a traffic lane which leaves at a junction ahead (lane drop) |
| 1012.1 | Continuous | Continuous | 100 | 100 | 150 | Not normally used | All-purpose roads with no hard shoulder or hard strip |
| 1012.1 | Continuous | Continuous | 150 | 150 | 200 | 18 | All-purpose roads with hard shoulder or hard strip |
| 1012.1 | Continuous | Continuous | 200 | 200 | 200 | 18 | Motorways |
| 1012.2 | Continuous | Continuous | 200 | 200 | 200 | 18 | Motorways |
| 1012.3 | Continuous | Continuous | 150 or 200 | 150 or 200 | 150 or 200 | 18 | All-purpose roads with hard strip or hard shoulder. The 200 mm wide line must be used when there is a hard shoulder |
NOTE: The prescribed colours for road studs and further guidance on spacing are detailed in paras 6.9 to 6.14.
​4.35 The following are examples of situations where the edge of carriageway marking might be particularly appropriate:
(i) where the demarcation between the carriageway and the verge is poor,
(ii) along lengths prone to fog and mist,
(iii) on heavily-trafficked single carriageway roads where headlamp dazzle is severe,
(iv) at sudden changes of carriageway width,
(v) on the approaches to narrow bridges,
(vi) on the approaches to bends indicated by bend warning signs,
(vii) at the back of a hard shoulder for use during contra-flow working. A 100 mm wide marking is prescribed for this purpose, and is generally laid 50 mm from the back of the hard shoulder. It may remain when the contra-flow has been removed, or
(viii) at traffic calming measures e.g. chicanes.
4.36 Edge lines are also recommended for use along the off side carriageway edge of unlit dual carriageway roads. The line should be laid with a gap of approximately 225 mm to the central reservation. The marking should not be carried across right turn lanes or breaks in the central reservation, where lines to diagram 1010 should be used. Where there is a hard strip, edge lines should be laid as indicated in figure 4-19. They should be used on all motorways in the positions shown in figure 4-20.
4.37 Where, because of the traffic importance or nature of the road, clearer delineation is required, red, uni-directional reflecting road studs may be used on the near side edge (see table 4-5) and, on dual carriageway roads, amber adjacent to the central reservation (see also para 6.10).
4.38 When depressible studs are used, they should always be placed on the carriageway side of the edge line to facilitate the cleaning action of the lenses. Non-depressible studs also benefit from trafficking to keep them free from road dirt and maintain their performance. Except at locations where experience has shown that placing the studs on the carriageway side of the edge line reduces their operational life to unacceptable levels, this may be better than placing them behind the line. Further guidance on the use of road studs is given in section 6.
RAISED PROFILE EDGE LINES
4.39 Raised profile lines are prescribed for use as an alternative to the edge of carriageway marking to diagram 1012.1. They consist of a continuous line marking with ribs across the line at regular intervals (see figure 4-9). The vertical edges of the raised ribs stand clear of the water film in wet conditions, improving retroreflective performance under headlight illumination. The ribs also provide an audible vibratory warning to drivers should they stray from the carriageway and run onto the marking.
4.40 Two types are specified, diagram 1012.2 for use on motorways and diagram 1012.3 for use on all-purpose roads with a hard strip or hard shoulder. The base marking must be no more than 6 mm high. The upstand of the ribs above the base marking must not exceed 11 mm for diagram 1012.2 and 8 mm for diagram 1012.3. The 500 mm spacing is suitable for most edge lines laid on the main carriageway. On motorways, the 250 mm spacing is recommended for use on slip roads. The closer spacing helps to maintain the rumble effect, offsetting the likely lower speed. Closer spacing is not used on all-purpose roads as it could present a hazard to cyclists. Diagram 1012.2 is always 250 mm wide. Diagram 1012.3 is usually 150 mm wide but is increased to 200 mm on all-purpose roads with hard shoulders.
4.41 Diagram 1012.3 is used on all-purpose roads, as the more aggressive rib of diagram 1012.2 has an unacceptable effect on cyclists and pedestrians.
​4.42 The edge lines of the following diagrams may also make use of raised profile lines:
(i) diagram 1040.3 - reduction of the number of lanes available,
(ii)diagram 1040.5 - approach to a termination of the hard shoulder, and
(iii) diagrams 1042 and 1042.1 - chevro nmarking, when used between main carriageway and slip road, or between bifurcating or converging carriageways (but not at a roundabout).
4.43 Raised profile markings must not be used as part of any marking or in any circumstances other than as specified above.
4.44 Raised profile markings should be discontinued where pedestrians and cyclists cross the road (e.g. at refuges) or at other places where cyclists are likely to cross them. A plain edge line to diagram 1012.1 should be used instead. This should normally extend a minimum distance of 1m either side of the crossing point.
4.45 Where gullies or similar features occur in the hard strip, cyclists may need to cross the adjacent edge line marking in order to avoid them. Any raised profile marking adjacent to such features should be replaced with a plain edge line for a distance of 10 mon each side of the gully.
4.46 When raised profile markings are laid on a curve of less than 1000 m radius, motorcyclists may find themselves in difficulty if there is a wide hardstrip or hard shoulder and they are tempted to cross onto it. The raised ribs tend to destabilise two-wheeled vehicles on appreciable bends. If there is any concern that motorcycles might frequently cut across the line, the ribs may be omitted, although the improved night-time wet weather visibility will obviously not then be available.
4.47 Drainage gaps of 100 to 150 mm should be provided at intervals of approximately 36 m where the longitudinal fall is flatter than 1 in 150, and there is a crossfall towards the profiled marking.
HATCHED MARKINGS
4.49 Hatched markings are prescribed as diagrams 1040, 1040.2, 1040.3, 1040.4 and 1040.5. They are also prescribed in diagrams 1013.3 and 1013.4 (see section 5 and paras 7.11 and 7.12). Two sets of dimensions are prescribed where the boundary line is broken, and are as set out in table 4-3 for diagrams 1004 and 1004.1, i.e. a 4 m mark and 2 m gap where the speed limit is 40 mph or less, and 6 m mark and 3m gap where the speed limit is more than 40mph. Regulation 12(4) exempts these diagrams from the requirement that alternative dimensions should correspond in order to maintain the shape of the marking. This allows the width of the boundary lines to be matched to those of the centre line or warning line at either end of the hatched marking. The spacing of the diagonal marks is linked to the length of the boundary lines; the closer spacing and the wider diagonal mark is used with the longer lines.
4.50 The tapers should be applied to each side of the centre line, whether it is straight or curved, at the rates specified in table 14-1. Diagrams 1040, 1040.3and 1040.4 may be preceded by the deflection arrow to diagram 1014 (see figures 4-13 and 13-6, and table 4-6). Arrows used with diagram 1040 should be positioned in the centre line and not in the opposing carriageway as with double white lines, i.e. as shown in figure 5-2 and not as in figure 5-3.
4.51 Diagram 1040 (figure 4-10) is intended to divide opposing flows of traffic on two-way roads. It may be used on the approach to refuges as a more emphatic alternative to the warning line, or to lead into diagram 1040.2. Where road studs are used, they must be white, and should be uni-directional. In diagrams 1040 and 1040.2, one of the boundary lines is omitted when the marking is placed alongside diagram 1049 delineating a bus or cycle lane.
4.52 Diagram 1040.2 (figure 4-11) may be used to separate opposing flows of traffic where the warning line is considered insufficient at hazards such as a bend or the brow of a hill. Unless this marking starts at a physical obstruction, e.g. a refuge, it should always be preceded by the tapered marking to diagram 1040. See paras 7.2 to 7.12 for guidance onthe use of hatched markings at a road junction.
4.53 Diagram 1040.3 (figure 4-12) indicates the approach to a place on a motorway, dual carriageway road or slip road where the number of lanes is reduced, or an area of carriageway not available to traffic. It is bounded by a 200 mm wide continuous edge marking which may be varied to diagram1012.2 or 1012.3. It may also be varied to 150 mm wide when used on all-purpose roads without hard shoulders. The layout for a main carriageway is shown in figure 4-13 (see figure 10-4 for slip roads).
​The studs at the edge line should remain amber and the spacing should be reduced to 9m along the length of road from the first deflection arrow encountered and along the hatching. Vertical signs to diagrams 872.1/876 should also be used in advance of the taper.
4.54 Diagram 1040.4 (figure 4-14) is used to markoff an area at the edge of the carriageway which drivers should not enter unless it is safe to do so. I twill commonly be used to guide traffic past build-outs in traffic calming schemes (see section 21). The tapers are set out in table 4-6; the shape of the marking may be varied to suit the road geometry, provided that the dimensions prescribed in diagram1040.4 are maintained, and may be reversed. The boundary to the left of the hatched area may be formed by diagram 1049 delineating the off-side edge of a cycle-lane.
​4.55 The marking to diagram 1040.5 (figure 4-15) should be used to indicate the termination of the hard shoulder. The edge marking is always 200 mm wide, whether it is used on motorways or on all-purpose roads with full width hard shoulders. Both longitudinal lines may be formed by the marking to diagram 1012.2 or 1012.3 as appropriate. Where there are two terminations in quick succession, the hard shoulder between them should be hatched off to discourage its use, as rejoining the motorway from the isolated section is likely to be difficult.
END OF DUAL CARRIAGEWAY
4.56 When a dual carriageway road changes to a single carriageway road other than at a junction, traffic should be guided into the slower lane when leaving the dual carriageway section. Details of appropriate vertical signing can be found in figures 5-1 and 5-2 of Chapter 4.
4.57 The reduction in the number of lanes and the taper to a single carriageway should be achievedusing hatching to diagrams 1040 and 1040.4. The boundary is derived as follows (see figure 4-16):
(i)the traffic leaving the dual carriageway section should be reduced to a single lane by marking off the outside lane at the inclinations shown in table 4-6. The full reduction should be achieved no later than the end of the central reservation, although it may occur earlier,
(ii)from the point in line with the end of the central reservation, derived in (i), the boundary should continue to the centreline of the single carriageway section at a taper no sharper than that used in (i) above; if the dual carriageway section leads into a right hand bend, it might be betterto use a longer taper length in order to merge tangentially with the apex,
(iii)for the carriageway leading to the dual carriageway section, the boundary line should extend from the end of the taper in (ii) to the central reservation.
Table 4-6 Taper and arrow details :
| 85 percentile speed (mph) | Taper | Length of arrow (m) | Distance from tip of arrow to start of taper (m) | Distance from tip of arrow to start of taper (m) | Distance from tip of arrow to start of taper (m) |
| 85 percentile speed (mph) | Taper | Length of arrow (m) | First arrow | Second arrow | Third arrow |
| Up to 30 | 1 in 40 | 4.5 | 13.75 | 43.75 | 79.75 |
| 31 to 40 | 1 in 40 | 4.5 | 19.75 | 55.75 | 109.75 |
| 41 to 50 | 1 in 55 | 6 | 21.00 | 66.00 | 138.00 |
| 51 to 60 | 1 in 45 | 6 | 30.00 | 84.00 | 165.00 |
| 61 to 70 | 1 in 50 | 9 | 37.50 | 91.50 | 190.50 |
NOTE: Different requirements apply to taper and arrow details for diagram 1040.3; see figure 4-13.
4.59 If road studs are used on the dual carriageway section, near side red studs should be continued through the merge. Amber studs should be used with the boundary line to diagram 1040.4; beyond the end of the central reservation the studs should revert to white, but be uni-directional.
CHEVRON MARKINGS
4.60 Diagram 1041 (figure 4-17) and its parallel-sided version (diagram 1041.1) are intended to separate streams of traffic travelling in the same direction, e.g. on the approach to a junction or to a pedestrian refuge in a one-way street. One of the boundary lines is omitted where the marking is placed alongside diagram 1049 delineating a bus or cycle lane.
4.61 Diagram 1042 (figure 4-18) is intended for use between a motorway or high standard all-purpose road and a slip road (see paras 10.2 to 10.12). It may also be used at the bifurcation or convergence of two motorways or similar roads. The parallel-sided version(diagram 1042.1) is used to indicate a segregated left turn lane (see paras 8.34 to 8.38). The width of the longitudinal lines may be 150 mm when the marking is used between two lanes at a roundabout (see figure 8-5) or on an all-purpose dual carriageway road without hard shoulders. Except at a roundabout, the boundary lines may be replaced with the marking shown in diagram 1012.2 or 1012.3 as appropriate.
​4.62 The chevrons in all diagrams must always point towards approaching traffic, i.e. in figures 4-17 and 4-18 they should be reversed when traffic is merging. Where road studs are used, these must be coloured red. Clearance between the inside edge of the boundary line and any kerb should be as indicated in para 4.23.
LAYOUT OF MARKINGS BETWEEN JUNCTIONS
4.63 The layout of road markings between junctions on high standard roads designed to TD 9 / 93 in Volume 6 of the Design Manual for Roads and Bridges (see para 1.4) is shown in figure 4-19 for all-purpose roads and figure 4-20 for motorways (all ​dimensions are in metres). These illustrate the placing of the lines in relation to the cross section of the road(see TD 27 / 96 for guidance on marking slip roads).
4.64 Edge of carriageway markings between the running lanes and the hard shoulder or hard strip may use raised rib profiles (diagram 1012.2 on motorways and 1012.3 on all-purpose roads; see paras 4.39 to 4.48 for details).
4.65 Edge lines should be accompanied by red unidirectional retro reflecting road studs adjacent to the hard shoulder or near side hard strip and, on motorways and dual carriageway roads, coloured amber adjacent to the central reservation. For use during contra-flow working, the amber studs may have red reflectors on the opposite face. The use of road studs in conjunction with road markings is dealt with in more detail in section 6.
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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.
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