Home | Press | Publications | What We Do | Who We Are | Search | Site Map | Contacts | Links
Publications

Publications A to Z

< Previous | Contents | Next >

Cycling by Design

12 . CONSTRUCTION AND MAINTENANCE

Introduction

12.1 Construction and maintenance are important aspects of any cycle facility. Needlessly expensive construction is wasteful, may be undesirable environmentally and prove, in turn, expensive to maintain. What may be considered an inconvenient and poor construction detail or minor defect by general traffic can represent a real hazard to cyclists. Winter Maintenance, including snow clearance and de-icing, may be a practicable proposition in an urban area but completely out of the question in remote rural locations. It is therefore important to ensure that not only are construction details and materials for the cycle facility appropriate but also that a suitable maintenance regime is established. This Chapter addresses these issues and outlines further work to be taken forward during the consultation period of ‘Cycling by Design.’

Construction

12.2 This issue may be dealt with in two parts:-

(i) Facilities within the carriageway, and

(ii) Facilities outwith the carriageway.

Within The Carriageway

12.3 Once the decision has been taken that there is adequate width available for a cycle facility to be provided within a carriageway then the designer should assess:

(i) The location of existing ironwork (manholes, gullies etc.), and

(ii) The standard of existing surface available (including colour contrast).

12.4 Ironwork: All existing ironwork should ideally be located outwith the extent of the cycle facility. Where this is not feasible ironwork should be reset so that it is flush with the carriageway surface. Any gratings should be reoriented so that they run at right angles to the direction of cycle flow and damaged ironwork should be replaced.

12.5 Where on new schemes it is anticipated that metre hardstrips will be used by cyclists, these should be free of ironwork. If gullies are required they should either be side-entry gullies or be offset from the edge of the carriageway running surface.

12.6 Surface: The surface of a cycle facility should have an even profile in accordance with Chapter 4 and be free of major defects. Where necessary, defects should be rectified in accordance with the maintenance requirements.

12.7 Coloured surfaces: The use of coloured surfacing to identify areas of the carriageway where other vehicles are discouraged from entering is recommended. There should however be a consistent approach to the use of surface colouring as indiscriminate use may reduce its effectiveness (Refer to Chapters 5 and 6) (See also DMRB 6.3.4).

12.8 The most common colours used are red and green but the final choice of colour should be made with regard to wider environmental considerations. The impact of bright colours in a rural environment can be both intrusive and downgrading to the surrounding landscape. It is also important to remember that standard white road markings will nearly always be used in combination with the coloured surface and the overall visual effect should therefore be considered.

12.9 There are two basic methods of achieving a coloured carriageway surface:-

(i) the use of coloured aggregates, fillers and binders in part of the wearing course mix;

(ii) surface application of a coloured material.

12.10 The final decision as to which type of coloured surfacing material should be used will be dependent on its location within the carriageway, the design standards specified for the carriageway and cost. The most common materials used are:-

(i) Thermoplastic paint;

(ii) Resin based materials with coloured chips;

(iii) Coloured macadam, and

(iv) Slurry seal.

12.11 In selecting the most appropriate material for a particular location the following should be assessed:-

(i) Skid resistance;

(ii) Adhesion to existing surface;

(iii) Colour retention;

(iv) Durability requirements;

(v) Ride quality, and

(vi) Cost

12.12 Thermoplastic Paint: The application of thermoplastic paint is recommended in locations where it may be machine laid on a clean, dry surface, in a 3mm coat with high aggregate content to ensure that an acceptable skid resistant surface may be provided.

12.13 The main advantages of Thermoplastic Paints are as follows:-

(i) Low initial cost;

(ii) Easy to apply;

(iii) Fast drying;

(iv) Excellent cohesion properties to most surfaces;

(v) Versatile;

(vi) Resistant to petrol or diesel spillage.

12.14 The main disadvantages of this type of surfacing are:

(i) Prone to poor quality finish;

(ii) May have poor wearing characteristics; and

(iii) May have short life span, resulting in high maintenance costs.

12.15 Although this surface is designed for use on carriageways it may be more suited to very lightly trafficked roads or cycle tracks.

12.16 Resin Based Materials: Surface dressing using resin based materials (epoxy or polyurethane) and coloured aggregates may be highly effective, however they also have a higher initial cost than both thermoplastic paints and slurry sealants.

12.17 There are a variety of options available for achieving coloured surface dressing. The most effective is to use a combination of naturally occurring coloured aggregate and coloured resin. This is particularly effective if a match between stone and resin can be achieved (Although a wide range of coated aggregates can be used, the colour tends to wear off revealing the natural aggregate colour).

12.18 Main advantages of Resin Based Materials:-

(i) Hard wearing characteristics;

(ii) Consistent colour;

(iii) Long term ageing properties;

(iv) High quality appearance and finish;

(v) Available in a wide range of colours.

12.19 Disadvantages of this system are:-

(i) Relatively expensive;

(ii) Under test conditions there have been some premature failures;

(iii) The performance of resin based treatment on concrete may not be acceptable because of the difficulty of obtaining a good bond between the binder and the concrete over large areas;

(iv) Colour changes may occur after 12 months due to the effects of UV light.

12.20 Coloured Macadam: Although the colours may be more muted than other types of coloured surfacing, coloured macadam is recommended for new construction due to its proven durability.

12.21 There are a variety of methods available for achieving a coloured wearing course. The recommended method is to use a colour pigment in the macadam/asphalt mix combined with an aggregate of complementary colour. The final material may be produced in a range of colours and should typically be laid to a depth of 20-30mm.

12.22 Coloured macadam should normally be provided in lieu of the standard wearing course on a bituminous basecourse. (If it is to be used for areas outwith the carriageway then it may be laid at a suitable thickness directly onto Type 1 sub-base material. Refer to Table 12.2).

12.23 An alternative method for achieving a coloured wearing course surface is to use a proprietary macadam type mix where the black bitumen binder is replaced with the use of a clear resin. This method may be combined with an artificially coloured aggregate. A disadvantage of this method is that the colour effect tends to wear off revealing the natural aggregate colour - thus reducing the colour effect.

12.24 Main advantages of coloured macadam are:-

(i) Hard wearing characteristics;

(ii) Becomes an integral part of the road;

(iii) Excellent long term ageing properties;

(iv) High quality appearance and finish, and

(v) Provides good ride quality

12.25 The main disadvantages are:-

(i) High cost compared to other types of coloured surfacing, and

(ii) May require the removal of the existing wearing course.

12.26 Slurry Seal: Pigmented slurry seal is one of the cheapest methods available for applying a coloured road surface. Slurry is best laid on a sound bituminous base or wearing course. It comes in a wide range of colours but red is normally the most economical.

12.27 The main advantages of slurry surfacing are:-

(i) Low capital cost;

(ii) Available in a wide range of colours, and

(iii) Quick setting.

12.28 The main disadvantages are:-

(i) Tendency for poor quality finish and wearing characteristics, resulting in higher costs.

(ii) May reduce the texture depth of the road surface and therefore the skid resistance.

12.29 Slurry material is generally recommended for use on untrafficked or lightly trafficked surfaces.

Outwith the Carriageway

12.30 Outwith the carriageway the designer should be able to exert greater control over the form of construction used. From first principles, a pavement is only required to spread the load from vehicles over the subgrade, such that it does not fail, and to protect the subgrade from environmental effects. For highway pavements the load spreading requirement predominates, however by using bound materials the sub-base and subgrade are automatically protected from any adverse environmental effects.

12.31 For cycleways the environmental effects tend to outweigh the requirement for load spreading capability. However, this does not mean that a thin, stiff surfacing on a granular base will automatically perform well as it may crack up under loading from occasional vehicle overrun, or from environmental effects such as shrinkage or freeze/thaw.

12.32 In an urban environment the risk of overrun may be high and the use of bound surfaces is the norm; and cycleway designs that are based on ‘highway’ practice may be justified. However in a rural environment such designs will not only look out of place but may not offer value for money due to the costs associated with transporting ‘standard’ materials from their places of manufacture and supply. (Maintenance costs also tend to be higher for the same reason). It is therefore suggested there may be more cost effective and environmentally friendly ways of constructing cycleways than using the previously accepted ‘standard’ forms of construction.

12.33 With this in mind it is intended to let a research project aimed at identifying a cost effective range of cycle track construction details that will make best use of materials available in rural Scotland. The research project, programmed to run concurrently with the Cycling by Design consultation period, will involve refinement of generic designs through a combination of constructability trials and in-situ and laboratory testing based on the trunk road interface sections of the NCN, particularly between Perth and Inverness.

12.34 In order that guidance is available during the consultation period a range of ‘standard’ construction details are presented. However care should be employed in their application as they may not offer the most appropriate or cost effective solution. Where applicable local knowledge should always be sought.

Table 12.1: Typical Construction - Urban Area

Figure 12.1: Typical Construction Urban Area

< Previous | Contents | Next >

The information contained on this WWW site is Crown Copyright but may be reproduced without formal permission or charge for personal or in-house use. Privacy and Content Disclaimer.

For general enquiries about this web site email ceu@scotland.gov.uk or fill out our online questionnaire.