DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME 6 SECTION 3 ROAD GEOMETRY HIGHWAY FEATURES PART 5 TD 51/17 SEGREGATED LEFT TURN LANES AND SUBSIDIARY DEFLECTION ISLANDS AT ROUNDABOUTS SUMMARY This document sets out the design requirements, methodology and advice for the provision of Segregated Left Turn Lanes and Subsidiary Deflection Islands for motorway and trunk road roundabouts. Measures to ensure safe operation for all road users are described. INSTRUCTIONS FOR USE This Requirement Document is to be incorporated in the Manual. 1. Remove existing Contents pages for Volume 6. 2. Insert new Contents pages for Volume 6 dated February 2017. 3. Insert TD 51/17 into Volume 6, Section 3, Part 5. 4. Please archive this sheet as appropriate. Note: A quarterly index with a full set of Volume Contents Pages is available separately from The Stationery Office Ltd. February 2017
DESIGN MANUAL FOR ROADS AND BRIDGES HIGHWAYS ENGLAND TD 51/17 TRANSPORT SCOTLAND LLYWODRAETH CYMRU WELSH GOVERNMENT DEPARTMENT FOR INFRASTRUCTURE NORTHERN IRELAND Segregated Left Turn Lanes and Subsidiary Deflection Islands at Roundabouts Summary: This document sets out the design requirements, methodology and advice for the provision of Segregated Left Turn Lanes and Subsidiary Deflection Islands for motorway and trunk road roundabouts. Measures to ensure safe operation for all road users are described.
Volume 6 Section 3 Registration of Amendments REGISTRATION OF AMENDMENTS Amend No Page No Signature & Date of incorporation of amendments Amend No Page No Signature & Date of incorporation of amendments February 2017
Registration of Amendments Volume 6 Section 3 REGISTRATION OF AMENDMENTS Amend No Page No Signature & Date of incorporation of amendments Amend No Page No Signature & Date of incorporation of amendments February 2017
DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME 6 SECTION 3 ROAD GEOMETRY HIGHWAY FEATURES PART 5 TD 51/17 SEGREGATED LEFT TURN LANES AND SUBSIDIARY DEFLECTION ISLANDS AT ROUNDABOUTS Contents Chapter 1. Introduction 2. Segregated Left Turn Lanes 3. Subsidiary Deflection Islands 4. Road Users Specific Requirements 5. References 6. Enquiries Annex A Traffic Signs and Road Markings references February 2017
Volume 6 Section 3 Chapter 1 Introduction 1. INTRODUCTION 1.1. Background 1.1.1. Segregated Left Turn Lanes can be used to improve the overall capacity of a roundabout entry where a significant volume of left turning traffic is expected on a particular approach. This is achieved through the provision of a dedicated lane, commencing on the approach to the roundabout, which is segregated from the circulatory carriageway and allows traffic to leave at the first exit without using the roundabout circulatory carriageway. 1.1.2. Subsidiary Deflection Islands can be used to introduce deflection at an existing roundabout entry where a junction improvement is proposed and where deflection in accordance to TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1] cannot be achieved. Deflection can be achieved through the provision of physical or non-physical islands in order to direct traffic. 1.1.3. This Requirements and Advice Document (RAD) includes several key changes from the previous Standard (TD 51/03), these are: a) Revised advice for the provision of Segregated Left Turn Lanes at three arm roundabouts and other roundabouts with asymmetrically arranged arms (Section 2.2 of this document). b) Inclusion of new requirements and advice for the provision of cycle facilities. c) The addition of Annex A summarising the traffic signs and road markings specifically identified in this RAD and their Traffic Signs Regulations and General Direction 2016 reference. 1.2. Scope and Purpose 1.2.1. This document provides details of the latest requirements and advice for Segregated Left Turn Lanes and Subsidiary Deflection Islands. 1.2.2. This document applies to all new roundabouts and to existing roundabouts that are to be modified or improved to include either Segregated Left Turn Lanes or Subsidiary Deflection Islands. 1.2.3. This document supersedes TD 51/03 (DMRB 6.3.5), which is hereby withdrawn. 1.3. Definitions, Acronyms and Abbreviations Cycle Track: a track separate from the main carriageway for use by cyclists. Cycle Tracks may be newly constructed or created through conversion of a footway; Cycle Design Vehicle: a vehicle used for the design of cycle facilities. The dimension of the Cycle Design Vehicle shall be a composite of the many types of cycle available (including standard cycles, solo tricycles, hand-cranked cycles, tandem cycles, recumbent cycles, trailer cycles (tandems with a hinge, usually with the rear seat to carry a child), cycles towing trailers, cargo cycles and cargo tricycles), used to provide design criteria; Non-physical Segregated Left Turn Lane: a dedicated left turn lane from a roundabout entry to the first exit, separated from the roundabout entry, circulatory carriageway and exit by means of a non-physical island delineated using road markings only (see Figure 2.1(a)). This definition also applies to segregated lanes at three arm and asymmetrically arranged roundabouts (see Section 2.2); February 2017 1/1
Chapter 1 Introduction Volume 6 Section 3 Non-physical Subsidiary Deflection Island: an island delineated by road markings alone, located between two entry lanes on the approach arm of a roundabout and shaped to direct, deflect and separate traffic movements onto the roundabout (see Figure 3.2(b)); Physical Segregated Left Turn Lane: a dedicated left turn lane from a roundabout entry to the first exit, separated from the roundabout entry, circulatory carriageway and exit by means of a kerbed island and associated road markings (see Figure 2.1(b)). This definition also applies to segregated lanes at three arm and asymmetrically arranged roundabouts (see Section 2.2); Physical Subsidiary Deflection Island: a raised kerbed island and associated road markings on the carriageway, located between two entry lanes on the approach arm of a roundabout and shaped to direct, deflect and separate traffic movements onto the roundabout (see Figure 3.2(a)); Traffic Deflection Island: a raised kerbed island and associated road markings on the carriageway, located between an entry and exit on the same roundabout arm. It should be shaped to direct and also separate opposing traffic movements onto and from a roundabout circulatory carriageway (see Figure 3.1); 1.4. Equality Impact Assessments 1.4.1. An assessment as to the applicability of an equality impact assessment (EqIA) shall be carried out for all designs. Where the assessment indicates that an EqIA is required, then the designer shall carry out an EqIA. Where the equality impact assessment indicates that people with protected characteristics may be disadvantaged or put at additional risk, the designer shall propose solutions to mitigate that risk. 1.5. Implementation 1.5.1. This document shall be used forthwith on all schemes for the construction, improvement and maintenance of trunk roads including motorways, currently being prepared, provided that, in the opinion of the Overseeing Organisation, this does not result in significant additional expense or delay progress. Design organisations should confirm its application to particular schemes with the Overseeing Organisation. 1.5.2. Requirements are identified by statements that include the word shall or must. Must is used in this RAD to denote a statutory obligation. Shall is used in this RAD to denote a requirement that is to be strictly followed. 1.5.3. In exceptional situations the Overseeing Organisation may be prepared to agree to a Departure from this document where the requirements are not realistically achievable. Design organisations proposing a non-compliance to a requirement should discuss this with the Overseeing Organisation at an early stage in design process. Proposals to adopt Departures from this document shall be submitted by the Design organisation to the Overseeing Organisation and formal approval received before incorporation into a design layout. 1.5.4. This document also includes advice in respect of the provision of Physical and Non-physical Segregated Left Turn Lanes and Physical and Non-physical Subsidiary Deflection Islands. Advice is identified by statements that include the word should. 1.6. Application in Devolved Administrations 1.6.1. This document applies to the motorway and all-purpose trunk road network in Wales and Scotland and those roads designated by the Overseeing Organisation in Northern Ireland. 1/2 February 2017
Volume 6 Section 3 Chapter 1 Introduction 1.6.2. In Northern Ireland all traffic signs and road markings must conform to the Traffic Signs Regulations (Northern Ireland) 1997 (TSRNI) [Ref 2] (see Annex A). 1.6.3. When applying this RAD on the motorway and all-purpose trunk road network in Scotland, reference shall be made to the Transport Scotland publication Roads for All: Good Practice Guide for Roads [Ref 3]. 1.7. General Principles 1.7.1. When designing Segregated Left Turn Lanes and Subsidiary Deflection Islands the general principles below shall be assessed: a) Certain geometric design features for Segregated Left Turn Lanes and Subsidiary Deflection Islands are related to the Design Speed of the upstream approach and downstream exit road as defined in TD 9 Highway Link Design (DMRB 6.1.1) [Ref 4]. At an existing junction the Design Speed shall be taken at a point upstream or downstream of the influence of the junction. Reference shall therefore be made to TD 9 Highway Link Design (DMRB 6.1.1) [Ref 4] in order to determine the appropriate Design Speed when applicable. b) Potential maintenance issues and the need for routine inspections. c) The level of provision required for pedestrians, cycle traffic and equestrians. 1.8. Feedback and Enquiries 1.10.1. Users of this document are encouraged to raise any enquiries and/or provide feedback on its content and usage to the dedicated Highways England team. The email address for all enquiries and feedback is: DMRB_Enquiries@highwaysengland.co.uk February 2017 1/3
Chapter 1 Introduction Volume 6 Section 3 1/4 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts 2. SEGREGATED LEFT TURN LANES AT ROUNDABOUTS 2.1 General 2.1.1. This chapter provides requirements and advice for the provision of Segregated Left Turn Lanes at roundabouts. A flowchart identifying the decision process for the inclusion of a Segregated Left Turn Lane is provided in Figure 2.10 of this document. 2.1.2. The two basic types of Segregated Left Turn Lane, namely segregation by road markings (non-physical) and physical segregation are shown in Figure 2.1. In both types of layout, vehicles are channelled into the left hand lane by road markings, supplemented by Advance Direction Signs. They proceed to the first exit without having to give way to other vehicles at the entry onto the roundabout. Segregation by road markings can be less effective because it can be subject to abuse by vehicles over-running the non-physical island. 2.1.3. The designer shall determine whether facilities for pedestrians, cycle traffic and equestrians are required at Segregated Left Turn Lanes and, if so, determine whether they can be catered for safely within the junction design. In some cases this may not be possible and designers shall consider alternative layouts. Requirements and advice relating to the provision for pedestrians, cycle traffic and equestrians are provided in Chapter 4 of this document. 2.1.4. The use of Segregated Left Turn Lanes requires the designer to consider a number of factors including road safety, capacity and facilities for pedestrians, cycle traffic and equestrians, and shall only be considered where their introduction: a) results in an increase in the overall capacity of the entry or roundabout in question when compared to alternative design or improvement measures; or b) results in an improvement to the junction s road safety i.e. a reduction in collision numbers or severity; and c) safely makes provision for pedestrians, cycle traffic and equestrians, where these user groups are permitted. 2.1.5. Only physical Segregated Left Turn Lanes shall be used in conjunction with traffic signals at roundabouts. 2.1.6. Non-physical Segregated Left Turn Lanes shall only be used on sections of highway where appropriate crossing facilities for pedestrians, cycle traffic and equestrians are provided away from the Segregated Left Turn Lane. 2.1.7. Uncontrolled crossing points shall not be provided across Segregated Left Turn Lanes. 2.1.8. Physical Segregated Left Turn Lanes shall only be provided at street lit junctions. 2.1.9. Physical Segregated Left Turn Lanes shall be used where vehicles using the Segregated Left Turn Lane have to give way at the exit. 2.1.10. Accesses and junctions shall not be located within Segregated Left Turn Lanes. February 2017 2/1
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 Figure 2.1 2/2 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts 2.2. Segregated Lanes at Three Arm Roundabouts and Roundabouts with Asymmetrically Arranged Arms 2.2.1. The provision of a segregated lane for the first exit at a three arm roundabout or roundabouts with four or more arms that are asymmetrically arranged can result in the provision of a segregated lane for straight ahead traffic movements. The use of a segregated lane for a straight ahead traffic movement could raise a number of issues that may result in unsafe layouts. The following potential issues shall be considered by the designer: a) high entry speed; b) higher speed of vehicles exiting the straight ahead lane compared with slower traffic leaving the roundabout circulatory carriageway, which can result in merging problems; c) the use of reverse curves both on the approach and through the roundabout and abrupt changes in crossfall; d) the difficulties presented to pedestrians, cycle traffic and equestrians when crossing the segregated lane; and e) potential difficulties in achieving the entry path radius requirements as identified in TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1]. 2.2.2. Designers shall ensure that the design of segregated lanes for straight ahead traffic movements reduces or mitigates the risks outlined above. If it is not possible to avoid the problems identified, the designer shall consider alternative layouts. 2.3. Traffic Flows and Capacity 2.3.1. When considering the use of Segregated Left Turn Lanes (or a segregated lane as described in paragraph 2.2.1), the total inflow at the roundabout entry, the proportion of vehicles taking the first exit and the number of entry lanes shall all be examined. The following procedure shall be used as an initial assessment to determine whether the provision of a Segregated Left Turn Lane or segregated lane merits further consideration. 2.3.2. The inclusion of a Segregated Left Turn Lane or segregated lane shall be assessed further if: L F E Where: L is the flow in vehicles per hour taking the first exit (Note: for flows greater than 1,500 vehicles per hour alternative layouts should be considered, see paragraph 2.3.6); F is the total entry arm inflow in vehicles per hour for the arm being considered for the Segregated Left Turn Lane; E is the number of proposed entry lanes onto the roundabout including the Segregated Left Turn Lane or segregated lane. February 2017 2/3
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 2.3.3. The designer shall assess the range of hourly flows to be used in this initial assessment. Typically this is likely to be peak hour traffic flows (AM and PM periods including for peak commuter and development usage). The initial assessment shall also consider forecast traffic flows taking account of background traffic growth and any nearby future development. Even if a peak period review satisfies the initial assessment formula above, the designer shall also consider off peak assessments to ensure that any potential disbenefits in the off peak periods do not outweigh peak hour benefits (e.g. reduced capacity at the give way line). The results of any assessment shall be carefully examined to ensure that the provision of a Segregated Left Turn Lane or segregated lane is the most appropriate form of improvement, compared with alternatives such as modifications to flare lengths or entry widths or traffic signal control. 2.3.4. For marginal cases where the value of F/E is close to L (refer to paragraph 2.3.2 of this document), the provision of a Segregated Left Turn Lane or segregated lane should be considered further, taking into account other factors such as potential road safety benefits. 2.3.5. The impact of introducing a Segregated Left Turn Lane or segregated lane shall be assessed taking into account the entry and exit treatments. Due to the interaction of the various elements of a Segregated Left Turn Lane or segregated lane, the use of traditional junction assessment computer programs may not be appropriate. Designers should consider the utilisation of a traffic micro-simulation program or similar technique to fully assess a Segregated Left Turn or segregated lane layout. 2.3.6. Two-lane Segregated Left Turn Lanes or two-lane segregated lanes shall not be used as these can result in high vehicle speeds and potential conflict at the diverge and merge point for the Segregated Left Turn Lane or segregated lane. Where flows taking the first exit are greater than 1500 vehicles per hour alternative junction forms or method of junction control shall be considered. 2.4. Geometric Design Requirements and Advice 2.4.1. The curve radius used for the Segregated Left Turn Lane is dependent on both the Design Speed of the approach road and site constraints. The driver s perception of the approach and Segregated Left Turn Lane radii is a determining factor in their approach speed. The designer shall therefore consider the need for speed reduction measures on the approach depending on the minimum curve radii used. Nearside curve radii of less than 10m shall not be provided. The exit radius used shall be greater than, or equal to, the entry radius. 2.4.2. Superelevation along the Segregated Left Turn Lane shall be applied in accordance with Table 3 and Chapter 3 of TD 9 Highway Link Design (DMRB 6.1.1) [Ref 4] subject to a maximum value of 5%. 2.4.3. The Desirable Minimum Stopping Sight Distance (SSD) throughout the Segregated Left Turn Lane shall be the lesser of (a) the SSD obtained from Table 3 of TD 9 Highway Link Design (DMRB 6.1.1) [Ref 4] for the Design Speed of the approach; or (b) the SSD given in Table 2.1 of this document appropriate to the maximum nearside curve radius. The Desirable Minimum SSD shall be applied to the section of Segregated Left Turn Lane between the end of the entry taper and the start of exit taper. 2.4.4. The maximum curve radius used to determine the SSD from Table 2.1, shall be the greater of either the entry or exit radius of the Segregated Left Turn Lane, these being defined as the nearside kerb radius that occurs immediately after the entry taper and immediately before the exit taper in the direction of travel. See Figures 2.6 and 2.7 for details of entry and exit tapers and nearside kerb radii. 2/4 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts Table 2.1: Desirable Minimum Stopping Sight Distances Maximum Nearside Kerb Radius (m) Desirable Minimum Stopping Sight Distance (m) Less than or equal to 20 35 21 to 40 70 41 to 80 90 81 to 100 120 101 to 120 160 Greater than 120 215 2.4.5. The carriageway widths specified in column 2 of Table 2.2 shall be used to accommodate the swept path of Heavy Goods Vehicles and hatched road markings shall be provided on the nearside of the curve to reduce the marked lane width to a minimum of 3.5m as shown in the typical cross sections on Figure 2.4. 2.4.6. Where physical segregation is introduced, this shall allow a left turn at the roundabout in the normal way from the non-segregated part of the approach as shown on Figure 2.1(b). 2.4.7. The Segregated Left Turn Lane width used shall be based on the minimum curve radius on the entry or exit. The carriageway width to be used depends on the length of the physical island. The widths specified in Table 2.2 shall be used, where a physical island in excess of 50m in length is proposed, the lane widths specified in Column 3 shall be used. Table 2.2: Minimum Nearside Kerb Radii and Carriageway Widths Minimum Nearside Kerb Radius (m) (1) Segregated Left Turn Lane Carriageway Width (for island lengths < 50m) (m) (2) Segregated Left Turn Lane Carriageway Width (for island lengths 50m) (m) (3) 10 8.4 10.9 15 7.1 9.6 20 6.2 8.7 25 5.7 8.2 30 5.3 7.8 40 4.7 7.2 50 4.4 6.9 75 4.0 6.5 100 3.8 6.3 > 100 3.5 6.0 Note: Carriageway widths in Table 2.2 are inclusive of the 0.3m offset (see paragraph 2.6.9). February 2017 2/5
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 2.4.8. At new Segregated Left Turn Lanes where cycle traffic is permitted to undertake the movement catered for by the Segregated Left Turn Lane, an off-road Cycle Track shall be provided (see Chapter 4 of this document). 2.4.9. 1m hardstrips shall not be provided on Segregated Left Turn Lanes. They shall be terminated at the start of the entry taper and started at the end of the exit taper as shown on Figure 2.5. Where hatched road markings are provided on the inside of the Segregated Left Turn Lane the hardstrip shall form the start of the hatching. 2.4.10. Where road markings are used to create the lane segregation, the overall width of the marked island shall be a minimum of 1.0m. Physical islands shall be a minimum width of 1.6m, subject to the provisions for pedestrians, cycle traffic and equestrians contained in Chapter 4 of this document and the requirements for bollards and traffic signs contained in paragraphs 2.5.4 and 2.5.5. Physical islands shall extend a minimum of 1.5m and 6m into the entry and exit roads respectively beyond the traffic deflection islands where pedestrians, cycle traffic or equestrians are prohibited, as shown on Figure 2.3(a). 2.4.11. Where pedestrians, cycle traffic and equestrians are permitted and therefore crossing facilities are provided adjacent to the roundabout entry or exit, the physical island shall extend a Desirable Minimum of 2.5m on both the entry and exit beyond the crossing point as shown on Figure 2.3(b). 2.4.12. Non-physical islands shall start and finish at the entry and exit road limits respectively as shown on Figure 2.1(a). On the approach and exit to the non-physical island hatched road markings as identified in paragraph 2.5.7 shall be provided. 2.4.13. Segregated Left Turn Lanes shall not be used at junctions where the approach road gradient is in excess of 4%. The gradient shall be measured in accordance with TD 9 Highway Link Design (DMRB 6.1.1) [Ref 4), applicable to the Design Speed of the approach measured back from the start of the entry taper. The longitudinal gradient along the Segregated Left Turn Lane shall not exceed 4%. 2.5 Traffic Signs and Road Markings 2.5.1. All traffic signs and road markings must conform to the Traffic Signs Regulations and General Directions (TSRGD) [Ref 5], or in Northern Ireland the Traffic Signs Regulations (Northern Ireland) (TSRNI) [Ref 2]. Annex A summarises the traffic signs and road markings specifically identified in this RAD including their Traffic Signs Regulations and General Direction 2016 and Traffic Signs Regulations (Northern Ireland) (TSRNI) references. Sign diagram numbers are generally the same but can occasionally differ between the two sets of regulations and in Northern Ireland designers shall read this standard in conjunction with the TSRNI or contact the Overseeing Organisation. Segregated Left Turn Lanes shall not be designed to induce high vehicle speeds. Any desirable speed reduction shall be achieved on the approach to the Segregated Left Turn Lane rather than within it. Where the Segregated Left Turn Lane follows a tight horizontal radius relative to the approach speed or there are substandard vertical alignment features, the use of SLOW road markings to Traffic Signs Regulations and General Directions (TSRGD) Diagram 1024 are recommended in conjunction with associated warning signs to TSRGD Diagram 512 (Bend ahead), plated with either TSRGD Diagram 511 (REDUCE SPEED NOW) or TSRGD Diagram 513.2 (Max speed). An appropriate supplementary plate should be provided with the sign to TSRGD Diagram 512 if the superelevation provided is insufficient. These traffic signs should be located to avoid sign clutter or confusion to drivers not using the Segregated Left Turn Lane. 2.5.2. The presence of a Segregated Left Turn Lane shall be signed on the approach using Advance Direction Signs. Designers shall refer to the Traffic Signs Manual Chapter 7 (paragraphs 5.43 and 5.44) [Ref 6] for guidance on the design of the route symbol. In the case of a lane drop layout, a left turn arrow to TSRGD Diagram 1038 shall be placed in the lane at its commencement and repeated if necessary until the entry 2/6 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts taper chevron marking commences. The use of road markings to TSRGD Diagram 1035 to supplement Advance Direction Signs shall also be provided. The latest requirements and advice on directional signs on the motorway and all-purpose road network should be obtained from the Overseeing Organisation. 2.5.3. Count down signs to TSRGD Diagrams 823, 824 and 825 shall only be provided on a dual carriageway approach to a roundabout when there is no risk of confusion between the distance to the commencement of the Segregated Left Turn Lane and the distance to the roundabout Give Way line. 2.5.4. Traffic signs and street furniture placed on physical islands should be limited as proliferation can create confusion, distract, reduce visibility, add to sign clutter and have maintenance and road safety implications. Reference shall be made to the Overseeing Organisations current standard for vehicle restraint systems for details on protection from roadside hazards and consideration shall be given to the Overseeing Organisations requirements for passive safety. 2.5.5. Where a physical island is to be provided, a plain faced lit bollard shall be installed at the start of the island. A minimum clearance of 0.6m between the edge of any sign or bollard and edge of the physical island shall be provided. Should the conspicuity of the physical island require further enhancement, the surface of the island should be finished in a colour that contrasts with the surfacing of the adjacent running carriageway. Hard surfaces should be provided for ease of maintenance and to avoid possible obstruction of visibility by uncut grass. 2.5.6. If the conspicuity of the approaches to physical Segregated Left Turn Lane islands requires enhancing, coloured surfacing under the TSRGD Diagram 1041 entry taper road markings should be considered. Reference should be made to TA 81 Coloured Surfacing in Road Layout (excluding traffic calming) (DMRB 6.3.4) [Ref 7]. Consideration should also be given to the enhancement of the TSRGD Diagram 1041 entry taper road markings themselves using specialist profiled and reflectorised materials to make them more conspicuous during the hours of darkness or during inclement weather. 2.5.7. The effectiveness of a non-physical island incorporated in a Segregated Left Turn Lane layout should be enhanced through the use of continuous, rather than broken, road markings (to TSRGD Diagram 1042), coloured surfacing and enhanced road marking materials that provide improved performance during the hours of darkness and in inclement weather (see paragraph 2.5.6). 2.5.8. The presence of pedestrian, cyclist and / or equestrian facilities shall be signed in accordance with the Traffic Signs Manual, Chapter 4 Warning Signs [Ref 8]. 2.5.9. Red reflecting road studs shall be used with road markings to TSRGD Diagram 1040.4, TSRGD Diagram 1041and TSRGD Diagram 1042 to indicate a road marking that should not be crossed. Guidance on the use of reflecting road studs is contained in the Traffic Signs Manual Chapter 5 [Ref 9]. 2.5.10. Where a Segregated Left Turn Lane has been widened to accommodate the swept paths of Heavy Goods Vehicles the designer shall incorporate measures to discourage high vehicle speeds or two vehicles attempting to use the lane side by side as result of the increased carriageway width. The widening shall be narrowed down on the nearside to provide a 3.5m minimum lane width through the use of hatching to TSRGD Diagram 1040.4. Hatching to TSRGD Diagram 1040.4 shall be a minimum width of 1.0m (see Figure 2.1). 2.5.11. Consideration should be given to increasing the conspicuity of hatching to TSRGD Diagram 1040.4 through the use of enhanced road marking materials that provide improved performance during the hours of darkness and in inclement weather (see paragraph 2.5.6) and coloured surfacing. Reference should be made to TA 81 Coloured Surfacing in Road Layout (excluding traffic calming) (DMRB 6.3.4) [Ref 7]. February 2017 2/7
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 2.6. Approach Layout 2.6.1. The approach arrangements shall consist of either a dedicated lane (see Figure 2.6) or diverge on the approach arm (see Figure 2.7). 2.6.2. Both dedicated lanes and merge/diverge arrangements on approach and exit can create difficulties for cycle traffic, therefore off-road Cycle Tracks shall be provided in locations where cycling is permitted. (See Figure 2.6 and Figure 2.7). 2.6.3. The entry arrangements shall consist of an approach taper, when a diverge is proposed, in accordance with Table 2.3, and as shown on Figures 2.7 and 2.8. Table 2.3: Segregated Left Turn Lane Approach Treatments Approach Type Approach Taper Entry Taper Dedicated Approach Lane No Yes Diverge Yes Yes 2.6.4. The approach taper is related to the Design Speed and minimum taper values contained in Table 2.4 shall be applied. Table 2.4: Minimum Approach Tapers Design Speed Minimum Taper 60 kph 1:10 > 60 kph 1:15 2.6.5. The entry taper length for the Segregated Left Turn Lane shall be provided in accordance with Table 2.5. The Segregated Left Turn Lane width shall be a minimum of 3.5m at the start of the entry taper, as shown on Figure 2.6. Table 2.5: Minimum Entry/Exit Taper Length Factors (see example in Figure 2.9) Design Speed (kph) Entry/Exit Taper Length Factor 50 20 60 20 70 20 85 25 100 30 2.6.6. Any widening required to accommodate the swept path of Heavy Goods Vehicles shall be developed along the length of the entry taper. The length of the entry taper shall be calculated using the method shown in paragraph 2.6.7. 2/8 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts 2.6.7. The length of the entry taper shall be dependent on the widening required to accommodate either the Segregated Left Turn Lane island width, subject to minimum widths of 1.0m for a non-physical and 2.2m (1.6m island width plus 0.3m marking offset on each side) for a physical island, or the widening required to accommodate the swept path of Heavy Goods Vehicles (Table 2.2). The larger of the two values shall be used to calculate the entry taper length using the factors contained in Table 2.5. 2.6.8. Figure 2.9 shows an example of how to calculate the entry taper length for a 1.6m wide physical island less than 50m in length, for a 70 kph single carriageway approach. 2.6.9. The taper for the hatching shall be developed asymmetrically on the Segregated Left Turn Lane side of the entry taper as shown on Figure 2.9 and shall terminate in a position offset 0.3m from the edge of a physical island as shown on Figure 2.2. The 0.3m offset may be reduced to 0.15m where the speed limit is 40mph or less and there is limited width between the island and the nearside kerb as shown in the Traffic Signs Manual Chapter 5 [Ref 9]. Figure 2.2 Termination of Taper Hatching at Physical Island (This Figure is intended for illustrative purposes only) 0.6m minimum clearance 0.3m offset to outside edge of the taper marking 0.4m Bollard 0.6m minimum clearance 0.3m offset to outside edge of the taper marking TSRGD Diag 1041 2.7. Exit Layout 2.7.1. The three basic types of exit layout from a Segregated Left Turn Lane are: a) Dedicated lane consisting of an exit taper as shown on Figure 2.6. b) Merge consisting of an exit and end taper as shown on Figure 2.7. c) Give-way as shown on Figure 2.8. 2.7.2. Merge exits shall not be provided where only a single lane exit is provided from the adjacent roundabout. Where only one exit lane has been provided from the roundabout, a give way arrangement shall be provided from the Segregated Left Turn Lane (see Figure 2.8). 2.7.3. The exit taper for the Segregated Left Turn Lane shall be provided in accordance with Table 2.5. The Segregated Left Turn Lane width shall be a minimum of 3.5m at the end of the exit taper, as shown on Figure 2.6. Any widening required to accommodate the swept paths of Heavy Goods Vehicles through the Segregated Left Turn Lane shall be removed along the length of the exit taper. As with the entry taper, the length of the exit taper shall be calculated by using the larger value when comparing the width of the February 2017 2/9
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 Segregated Left Turn Lane island with the width reduction required between the start and end of the exit taper, as shown on Figure 2.9. 2.7.4. The taper for the hatching shall be developed asymmetrically on the Segregated Left Turn Lane side of the exit taper as shown on Figure 2.9 and shall terminate in a position offset from the edge of a physical island in accordance with paragraph 2.6.9 of this document. 2.7.5. TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1] advises that at the beginning of a roundabout exit, its width should allow for an extra traffic lane over and above that of the link downstream. This extra width should be reduced on the nearside, normally at a taper of 1:15 to 1:20. Where a Segregated Left Turn Lane is present, the exit width reduction shall be completed upstream of the end of the Segregated Left Turn Lane exit taper. This may require extending the Segregated Left Turn Lane exit taper to accommodate the roundabout exit width reduction. 2.7.6. The end taper is related to Design Speeds and the minimum taper values contained in Table 2.6 shall be provided. Table 2.6: Minimum End Tapers Design Speed Minimum Taper 60 kph 1:10 > 60 kph 1:15 2.7.7. A give way exit from a Segregated Left Turn Lane shall be located as close as practicable to the roundabout, at a minimum entry angle of 20. The entry angle is defined as the angle between the line of the give way marking to TSRGD Diagram 1003A and the centreline of the vehicle at the give way as shown on Figure 2.8. The position of the vehicle at the give way shall be determined by carrying out a swept path analysis. 2.7.8. Where traffic signs and street furniture are placed on the physical island in the vicinity of the exit, they shall be located so as not to obstruct road user visibility between the Segregated Left Turn Lane exit and adjacent roundabout exit lane. 2.8. Non-physical Segregated Left Turn Lanes 2.8.1. Non-physical Segregated Left Turn Lanes can be subject to abuse by drivers crossing the hatched island area resulting in conflicts in the vicinity of the Segregated Left Turn Lane. Therefore a physical island shall be provided where possible. 2.8.2. The carriageway widths specified in Table 2.2 shall be used to accommodate the swept path of Heavy Goods Vehicles. 2.8.3. Raised or domed surfaces, flush kerbs or infilling with marking material to reinforce road markings shall not be used (with the exception of coloured infill surfacing -see paragraph 2.5.7). 2/10 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts Figure 2.3 February 2017 2/11
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 Figure 2.4 Figure 2.5 2/12 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts Figure 2.6 February 2017 2/13
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 Figure 2.7 2/14 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts Figure 2.8 February 2017 2/15
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 Figure 2.9 2/16 February 2017
Volume 6 Section 3 Chapter 2 Segregated Left Turn Lanes at Roundabouts Figure 2.10 Example of Flow Chart Decision Process For Incorporation of Subsidiary Deflection Island Yes Is L F/E (See Section 2.3) No Would a SLTL improve overall junction capacity? (See Section 2.3) No Is there likely to be a material road safety benefit if a SLTL is provided? (See Para. 2.1.4) No Consider alternative measures to improve capacity Yes Yes Are pedestrians, cyclists and equestrians permitted to use the highway? See Para. 2.4.8 and Chapter 4) No Is the junction lit or proposed to be lit? (See Para. 2.1.8) No Consider a Non-physical SLTL Yes Yes Can off-road pedestrian, cyclists and equestrian facilities be provided parallel to the SLTL? (See Chapter 4) No Consider a Physical SLTL Consider alternative measures to improve capacity Yes Can pedestrian, cyclist and equestrian facilities be provided away from the SLTL? No Is there sufficient width to provide a Physical SLTL island with controlled provision for pedestrian, cyclist and equestrian crossing facilities? (See Para. 4.3.3 and Para. 4.4.5) No Yes Yes Is the junction lit or proposed to be lit? (See Para. 2.1.8) Yes Consider a Physical SLTL No Consider alternative measures to improve capacity NOTES: 1. Traffic Signal Control can only be utilised at Physical Segregated Left Turn Lanes. (See Para. 2.1.5 and Section 4.2) 2. Give way exit arrangements can only be utilised at Physical Segregated Left Turn Lanes. (See Para. 2.1.9) February 2017 2/17
Chapter 2 Segregated Left Turn Lanes at Roundabouts Volume 6 Section 3 2/18 February 2017
Volume 6 Section 3 Chapter 3 Subsidiary Deflection Islands 3. SUBSIDIARY DEFLECTION ISLANDS 3.1. General 3.1.1. This chapter provides requirements and advice for the provision of Subsidiary Deflection Islands at roundabouts and the geometric features to be considered in their design. Many of the features are considered separately, and designers shall adopt a systematic approach to achieve a satisfactory design incorporating only the appropriate features. A flowchart identifying the decision process for the inclusion of a Subsidiary Deflection Island is provided in Figure 3.6 of this document. 3.1.2. A Subsidiary Deflection Island is a method for introducing deflection at a roundabout entry. It shall not be used in the design of new roundabout junctions, but may be considered as part of an improvement scheme to an existing roundabout to overcome existing substandard entry path curvature. Subsidiary Deflection Islands, as shown on Figure 3.1, shall only be considered where the required deflection as defined and measured according to TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1] cannot be achieved through conventional design measures. 3.1.3. In urban areas, the restrictions on space available coupled with the turning width requirements of Heavy Goods Vehicles may result in normal roundabouts (as defined in TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1]), which do not provide sufficient entry deflection to the left by means of the central island alone. In these cases deflection should be generated by means of enlarged traffic deflection islands (Figure 3.4) or, if these cannot be provided at existing roundabouts, by Non-physical Subsidiary Deflection Islands in the entry as shown on Figure 3.5. 3.1.4. The designer shall take into account, the needs of pedestrians, cycle traffic and equestrians. Non-physical Subsidiary Deflection Islands shall not be used on sections of highway where pedestrians, cycle traffic and equestrians are known to cross. Suitable measures and advice relating to provision for pedestrians, cycle traffic and equestrians are addressed in Chapter 4 of this document. 3.1.5. Physical Subsidiary Deflection Islands shall only be used at street lit junctions. 3.1.6. At lit junctions Physical Subsidiary Deflection Islands should be prioritised, as Non-physical Subsidiary Deflection Islands are subject to abuse by drivers crossing the hatched road markings and therefore are less effective than physical islands. The designer shall only consider Non-physical Subsidiary Deflection Islands where the option for a Physical Subsidiary Deflection Island has been discounted for reasons of available space or safety. 3.2. Geometric Design Requirements and Advice 3.2.1. Physical Subsidiary Deflection Islands shall be a minimum width of 1.6m, subject to the provisions for pedestrians, cycle traffic and equestrians contained in Chapter 4 of this document. Non-physical Subsidiary Deflection Islands shall be a minimum width of 1m. Physical Subsidiary Deflection Islands shall be offset a minimum of 2.4m from the roundabout give-way line to avoid the lit bollard obstructing visibility. The island shall be a minimum total length of 5m as shown on Figure 3.2. 3.2.2. The entry path curvature shall be measured in accordance with the guidance contained in TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1] and as shown on Figure 3.3, where a Subsidiary Deflection Island is provided. February 2017 3/1
Chapter 3 Subsidiary Deflection Islands Volume 6 Section 3 Figure 3.1 3/2 February 2017
Volume 6 Section 3 Chapter 3 Subsidiary Deflection Islands Figure 3.2 February 2017 3/3
Chapter 3 Subsidiary Deflection Islands Volume 6 Section 3 3.3. Traffic Signs and Road Markings 3.3.1. All traffic signs and road markings must conform to the Traffic Signs Regulations and General Directions (TSRGD) [Ref 5], or in Northern Ireland the Traffic Signs Regulations (Northern Ireland) (TSRNI) [Ref 2]. Sign diagram numbers are generally the same but can occasionally differ between the two sets of regulations and in Northern Ireland designers shall read this standard in conjunction with the TSRNI or contact the Overseeing Organisation (see Annex A). All traffic signs and road markings shall also be designed and applied in accordance with the Traffic Signs Manual including Chapter 3 Regulatory Signs [Ref 10], Chapter 4 Warning Signs [Ref 8], Chapter 5 Road Markings [Ref 9] and Chapter 7 Design of Traffic Signs [Ref 6]. 3.3.2. Non-physical Subsidiary Deflection Islands are areas defined by road markings and road studs only. Road markings shall not be raised. Areas of solid marking material shall not be used (with the exception of coloured surfacing used under areas of hatching -see paragraph 3.4.1 and TA 81, Coloured Surfacing in Road Layout (excluding traffic calming) (DMRB 6.3.4) [Ref 7]. 3.3.3. Road markings to TSRGD Diagram 1041 shall be used to guide vehicles past the physical island, see Figure 3.2. The approach hatching for both Physical and Non-physical Subsidiary Deflection Islands shall be in accordance with Table 3.1. Table 3.1: Approach Hatching Taper Design Speed (kph) Approach Hatching Taper 50 1:40 60 1:40 70 1:45 85 1:45 100 1:50 3.3.4. The approach hatching shall be developed symmetrically and shall terminate at a position offset from each side of a Physical Subsidiary Deflection Island in accordance with paragraph 2.7.4 of this document. The road markings to TSRGD Diagram 1041 shall continue at full width from the end of the island up to the roundabout give way as shown on Figure 3.2. 3.3.5. Where a Physical Subsidiary Deflection Island is to be provided, a plain faced lit bollard shall be installed at the start of the island. A minimum clearance of 0.6m between the edge of any sign or bollard and edge of carriageway shall be provided. Should the conspicuity of the Physical Subsidiary Deflection Island require further enhancement, the surface of the island should be finished in a colour that contrasts with the surfacing of the adjacent running carriageway. Hard surfaces should be provided for ease of maintenance and to avoid possible obstruction of visibility by uncut grass. 3.4. Road Safety 3.4.1. If road safety concerns have been identified in respect of visibility to the Subsidiary Deflection Island, the conspicuity of the island should be enhanced through the use of coloured surfacing (TA 81, Coloured Surfacing in Road Layout (excluding traffic calming) (DMRB 6.3.4) [Ref 7]) within the hatched road marking on the approach (however it should be noted that coloured surfaces has limited benefit during the hours of darkness although it can be enhanced by using reflective glass bead). 3/4 February 2017
Volume 6 Section 3 Chapter 3 Subsidiary Deflection Islands 3.4.2. Red reflecting road studs shall be used in conjunction with road markings to TSRGD Diagram 1041. Guidance on the use of reflecting road studs is contained in the Traffic Signs Manual Chapter 5 [Ref 9]. 3.4.3. Subsidiary Deflection Islands shall be correctly signed and marked in order that the island itself does not present a hazard to road users. Figure 3.3 February 2017 3/5
Chapter 3 Subsidiary Deflection Islands Volume 6 Section 3 Figure 3.4 3/6 February 2017
Volume 6 Section 3 Chapter 3 Subsidiary Deflection Islands Figure 3.5 February 2017 3/7
Chapter 3 Subsidiary Deflection Islands Volume 6 Section 3 Figure 3.6 Example of Flow Chart Decision Process For Incorporation of Subsidiary Deflection Island Is the scheme an improvement to an existing roundabout layout? (See Para. 3.1.2) No Use TD 16 design procedures for new roundabout layouts Yes Can deflection be provided using conventional TD 16 measures (See Para. 3.1.2) No Is there scope to introduce a SDI on the entry arm? No Consider alternative measures Yes Yes Are pedestrians, cyclists and equestrians known to use the highway? (See Para. 3.1.4) No Is the junction lit or proposed to be lit? (See para. 3.1.5) No Consider a Non-physical SDI Yes Yes Are pedestrian, cyclist and equestrian crossing facilities provided away from the SDI? (See Para. 3.1.4) Yes No Consider a Physical SDI Is there sufficient width to provide a crossing facility on the SDI for pedestrians, cyclists and equestrians? (See Para. 3.2.1) No Is the junction lit or proposed to be lit? (See para. 3.1.5) No Consider a Non-physical SDI Yes Is the junction lit or proposed to be lit? (See Para. 3.1.5) No Yes Yes Consider a Physical SDI Consider a Physical SDI 3/8 February 2017
Volume 6 Section 3 Chapter 4 Road Users Specific Requirements 4. ROAD USERS SPECIFIC REQUIREMENTS 4.1. General 4.1.1. As a scheme designed to this document will result in a permanent change to the highway network, pedestrian, cycle traffic and equestrian facilities shall be assessed in line with DMRB HD 42 (DMRB 5.2.5) [Ref 11]. Road safety shall be assessed in accordance with HD 19 Road Safety Audit (DMRB 5.2.2) [Ref 12]. 4.2. Specific Requirements and Advice for Traffic Signal Crossings 4.2.1. Where a traffic signal controlled crossing is provided at a Segregated Left Turn Lane and the signal phasing on the Segregated Left Turn Lane runs independently to the other approach lanes, a staggered crossing should be used. 4.2.2. Staggered crossings shall be designed so that the central refuge can accommodate the design parameters for the Cycle Design Vehicle and a two-way Cycle Track (including pedestrian and equestrian facilities where appropriate). 4.3. Specific Requirements and Advice for Pedestrians 4.3.1. Where a pedestrian route crosses a Segregated Left Turn Lane or Subsidiary Deflection Island, appropriate facilities shall be provided in accordance with the guidance contained in TA 68 The Assessment and Design of Pedestrian Crossings (DMRB 8.5.1) [Ref 13], TA 90 Geometric Design of Pedestrian, Cycle and Equestrian Routes, [Ref 14], TD 16 Geometric Design of Roundabouts (DMRB 6.2.3) [Ref 1] and TD 50 The Geometric Layout of Signal Controlled Junctions and Signalised Roundabouts (DMRB 6.2.3) [Ref 15]. TA 57 Roadside Features (DMRB 6.3.3) [Ref 16] contains guidance on kerbing and guardrails. Guidance on the use of tactile paving surfaces is available from the Department for Transport. In Scotland reference shall also be made to the Transport Scotland publication Roads for All: Good Practice Guide for Roads [Ref 3]. 4.3.2. Suitable controlled crossings or grade separated facilities shall be provided where pedestrians are expected to cross a segregated left turn lane. Where controlled crossing are used on the segregated left turn lane, other crossing facilities at the junction should be consistent and both controlled and uncontrolled facilities shall not be used on the same arm. Crossing facilities at Subsidiary Deflection islands shall also be consistent with adjacent crossing facilities on the same junction arm. 4.3.3. Islands shall be of sufficient size to accommodate the anticipated peak number of pedestrians. Where a pedestrian refuge or Physical Segregated Left Turn Lane island is provided, it shall be a minimum width of 2.0m and the hatching a minimum width of 2.6m (or 2.3m where the speed limit is 40mph or less) adjacent to the refuge to allow for the appropriate offset as shown in the Traffic Signs Manual Chapter 5 [Ref 9] and on Figure 2.2. 4.3.4. Subsidiary Deflection Islands can appear to create refuges that encourage pedestrians to cross at these locations even if they are not intended as a pedestrian facility. Where Subsidiary Deflection Islands are intended to be used by pedestrians, they shall be physical islands and measures should be taken to direct pedestrians to specific crossing points. Where the islands are not intended for pedestrian use, measures should be taken to discourage pedestrians from using them and instead direct pedestrians to the appropriate crossing points. 4.3.5. Dropped kerbs shall be provided at pedestrian crossing points at Segregated Left Turn Lanes and Subsidiary Deflection Islands. Tactile paving shall be provided in accordance with latest Department for February 2017 4/1
Chapter 4 Road Users Specific Requirements Volume 6 Section 3 Transport guidance. In Scotland reference shall be made to the Transport Scotland publication Roads for All: Good Practice Guide for Roads [Ref 3]. 4.4. Specific Requirements and Advice for Cycle Traffic 4.4.1. Additional information on the provision of dedicated facilities for cycle traffic is contained in TA 90 The Geometric Design of Pedestrian, Cycle and Equestrian Routes (DMRB 6.3.5) [Ref 14] and TA 91 Provision for Non-motorised Users (DMRB 5.2.4) [Ref 17]. Latest requirements and advice in respect of cycle traffic and the motorway and all-purpose trunk road network in England can be obtained from Highways England. In Scotland reference shall also be made to the Transport Scotland publication Cycling by Design 2010 [Ref 18] 4.4.2. When designing for cycle traffic at new Segregated Left Turn Lanes, designers shall provide off-road Cycle Tracks to minimise road safety related risks at the start and end of the Segregated Left Turn Lane. 4.4.3. Designers shall refer to the Overseeing Organisations specific requirements and advice for the provision of cycle facilities. These facilities require appropriate traffic signing to both instruct cycle traffic and warn approaching motorists. 4.4.4. Where a Physical Subsidiary Deflection Island is proposed and some cycle traffic is likely to remain on the road, a minimum carriageway width of 4.5m shall be maintained between carriageway edge kerbs or any carriageway edge road markings. 4.4.5. Where cycle traffic is expected to cross Physical Segregated Left Turn Lane islands, as shown on Figure 4.1, or a Physical Subsidiary Deflection island, a minimum island width of 3.0m shall be provided. 4.5. Specific Requirements and Advice for Equestrians 4.5.1. Designers should provide for equestrians away from the immediate vicinity of roads. However, where improvements for equestrians within the highway boundary are identified as desirable or necessary, designers shall make reference to the advice in TA 90 The Geometric Design of Pedestrian, Cycle and Equestrian Routes (DMRB 6.3.5) [Ref 14] and TA 91 Provision for Non-motorised Users (DMRB 5.2.4) [Ref 17]. 4.6. Landscaping 4.6.1. The use of planting and landscaping techniques can be used to assist in directing pedestrians, cycle traffic and equestrians to the appropriate crossing points at roundabouts, and to discourage them from crossing at unsafe locations. 4.6.2. Planting and landscaping shall not obstruct forward visibility around Segregated Left Turn Lanes or intervisibility at crossings for pedestrians, cycle traffic and equestrians. 4.6.3. When proposing planting and landscaping areas, designers should specify species that minimise future maintenance. 4.7. Abnormal Load Routes 4.7.1. If the roundabout is situated on an abnormal load route the use of Physical Segregated Left Turn islands and Physical Subsidiary Deflection islands shall be assessed to ensure sufficient carriageway width between kerbs can be provided. If sufficient carriageway width cannot be provided Non-physical islands should be considered providing that other conditions laid down in Figures 2.10 and 3.6 and elsewhere within this document are met. 4/2 February 2017
Volume 6 Section 3 Chapter 4 Road Users Specific Requirements 4.8. Buses 4.8.1. The designer shall assess the use of bus only Segregated Left Turn Lanes to provide priority for left turning buses at roundabout junctions. Factors including the number of buses using the dedicated lane and any detrimental impact on the overall capacity of the roundabout entry and affected exit shall be taken into account. 4.8.2. Bus stops and lay-bys shall not be located within Segregated Left Turn Lanes. February 2017 4/3
Chapter 4 Road Users Specific Requirements Volume 6 Section 3 Figure 4.1 4/4 February 2017
Volume 6 Section 3 Chapter 5 References 5. REFERENCES Table 5.1: Normative References Ref Title Publisher 1 Design Manual for Roads and Bridges, Volume 6, Section 2, Part 3: TD 16, Geometric Design of Roundabouts 2 Traffic Signs Regulations, (Northern Ireland) 1997, including amendments 1999, 2002, 2003, 2005(2), 2006, 2007, 2008, 2009 and 2013 The Stationery Office 3 Roads for All: Good Practice Guide for Roads, July 2013 Transport Scotland 4 Design Manual for Roads and Bridges, Volume 6, Section 1, Part 1: TD 9, Amendment No 1: Highway Link Design 5 The Traffic Signs Regulations and General Directions (2016) 6 Traffic Signs Manual, Chapter 7: The Design of Traffic Signs (2013) 7 Design Manual for Roads and Bridges, Volume 6, Section 3, Part 4: TA 81, Coloured Surfacing in Road Layout (excluding traffic calming) 8 Traffic Signs Manual, Chapter 4: Warning Signs (2013) 9 Traffic Signs Manual, Chapter 5: Road Markings (2003) 10 Traffic Signs Manual, Chapter 3: Regulatory Signs (2008) 11 Design Manual for Roads and Bridges, Volume 5, Section 2, Part 5: HD 42, Non-motorised User Audits 12 Design Manual for Roads and Bridges Traffic Signs Manual, Volume 5, Section 2, Part 2: 19 Road Safety Audit 13 Design Manual for Roads and Bridges, Volume 8, Section 5, Part 1: TA 68, The Assessment and Design of Pedestrian Crossings 14 Design Manual for Roads and Bridges, Volume 6, Section 3, Part 5: TA 90, The Geometric Design of Pedestrian, Cycle and Equestrian Routes 15 Design Manual for Roads and Bridges, Volume 6, Section 2, Part 3: TD 50, The Geometric Layout of Signal Controlled Junctions and Signalised Roundabouts 16 Design Manual for Roads and Bridges, Volume 6, Section 3: TA 57, Roadside Features 17 Design Manual for Roads and Bridges, Volume 5, Section 2, Part 4: TA 91, Provision for Non-motorised Users The Stationery Office 18 Cycling by Design 2010 (Revision 1, June 2011) Transport Scotland February 2017 5/1
Chapter 5 References Volume 6 Section 3 5/2 February 2017
Volume 6 Section 3 Chapter 6 Enquiries 6. ENQUIRIES Approval of this document for publication is given by: Highways England Temple Quay House The Square Temple Quay Bristol BS1 6HA M WILSON Chief Highway Engineer Transport Scotland 8th Floor, Buchanan House 58 Port Dundas Road Glasgow G4 0HF R BRANNEN Director, Trunk Road and Bus Operations Welsh Government Transport Cardiff CF10 3NQ S HAGUE Deputy Director Network Management Division Department for Infrastructure Clarence Court 10-18 Adelaide Street Belfast BT2 8GB P B DOHERTY Director of Engineering All technical enquiries or comments on this Document should be sent to DMRB_Enquiries@highwaysengland.co.uk February 2017 6/1
Chapter 6 Enquiries Volume 6 Section 3 6/2 February 2017
Volume 6 Section 3 Annex A Traffic Signs and Road Markings References ANNEX A: TRAFFIC SIGNS AND ROAD MARKINGS REFERENCES General A1 The following table identifies the Traffic Signs and Road Markings specifically referenced in this RAD, their Traffic Signs Regulations and General Direction 2016 reference and the equivalent reference in the Traffic Signs Regulations (Northern Ireland) 1997 publication (including amendments 1999, 2002, 2003, 2005 (2), 2006, 2007, 2008, 2009 and 2013). Traffic Signs Regulations and General Directions 2016 Diag. Layout Schedule Part Item No. Traffic Signs Regulations Northern Ireland (1997) Traffic Sign or Road Marking Description 511 2 3 1 511 512 2 2 8 512 513.2 2 3 2 513.2 Reduction in speed necessary at a hazard ahead Bend ahead (Alternative types) Maximum speed in mph advised at a bend or other hazard 602 9 2 2 602 Give way sign 823 11 2 21 823 824 11 2 21 824 825 11 2 21 825 Distance in hundreds of yards to a roundabout or the next point at which traffic may leave a route Distance in hundreds of yards to a roundabout or the next point at which traffic may leave a route Distance in hundreds of yards to a roundabout or the next point at which traffic may leave a route February 2017 A/1
Annex A Traffic Signs and Road Markings References Volume 6 Section 3 Traffic Signs Regulations and General Directions 2016 Diag. Layout Schedule Part Item No. Traffic Signs Regulations Northern Ireland (1997) Traffic Sign or Road Marking Description 955 3 2 28 955 Route for use by pedal cycles only 957 3 2 32 957 1003A 9 6 3 1003 1004 11 4 2 1004 Route comprising two ways for use by pedal cycles only and by pedestrians only Vehicular traffic must give way Longitudinal road marking 1004.1 11 4 3 1004.1 Longitudinal road marking 1005 11 4 4 1005 Longitudinal road marking 1005.1 11 4 5 1005.1 Longitudinal road marking 1010 11 4 10 1010 Longitudinal road marking 1024 11 4 15 1024 Vehicular traffic should proceed with caution because of potential danger ahead 1029 11 4 18 1029 Direction in which pedestrians should look for approaching traffic A/2 February 2017
Volume 6 Section 3 Annex A Traffic Signs and Road Markings References Traffic Signs Regulations and General Directions 2016 Diag. Layout Schedule Part Item No. Traffic Signs Regulations Northern Ireland (1997) Traffic Sign or Road Marking Description 1035 11 4 19 1035 Appropriate traffic lanes for different destinations 1038 11 4 20 1038 1040.4 11 4 25 1040.4 1041 11 4 27 1041 Appropriate traffic lanes for different manoeuvres (Longitudinal marking) Part of the carriageway adjacent to the edge which vehicular traffic should not enter unless it is seen by the driver to be safe to do so Part of the carriageway where vehicular traffic passes in the same direction on both sides of the marking, and should not enter the area covered by the marking unless it is seen by the driver to be safe to do so February 2017 A/3
Annex A Traffic Signs and Road Markings References Volume 6 Section 3 Traffic Signs Regulations and General Directions 2016 Diag. Layout Schedule Part Item No. Traffic Signs Regulations Northern Ireland (1997) 1042 9 6 22 1042 1049B 9 6 7 1049 1049.1 9 6 8 1049.1 Traffic Sign or Road Marking Description Division of traffic lanes on a length of carriageway, or between the main carriageway and slip road, of a motorway or all-purpose dual carriageway road, or part of the carriageway between two lanes at a roundabout which vehicular traffic must not enter except in emergency Boundary of a mandatory cycle lane or division of a route into that part reserved for pedal cycles Division of a route into that part reserved for pedal cycles and that part reserved for pedestrians 1057 11 4 28 1057 Cycle lane, track or route A/4 February 2017