Prince Albert Road Towpath Ramp, Camden Feasibility Report

Transcription

1 Prince Albert Road Towpath Ramp, Camden Feasibility Report Function Location: RE-004 Date: 25 October 2012 Report No: 5016-UA UT31R-03

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3 Prince Albert Road Towpath Ramp, Camden Feasibility Report Name Signature Prepared By: Andrew Branch Checked By: Andrew Branch Approved By: Clive James Report No 5016-UA UT31R-03 Date 25 October 2012 Issue Status: Issue Status Dates 01 First Issue 24/02/ Draft Incorporating client comments 26/03/ Final issue 25/10/ UA UT31-R-01

4 CONTENTS 1 INTRODUCTION CONSTRAINTS & OPPORTUNITIES Topographical Existing Pedestrian Ramp Pedestrian Crossing Facilities Environment and Heritage Utilities and Services within the site Improvement in Wayfinding REVIEW OF DESIGN STANDARDS RAMP OPTIONS Option 1: Refurbishment of Existing Ramp Option 2: 2m Wide Ramp Option 3: 3m Wide Ramp Option 4: Do Nothing Option Other Considerations Access for Cyclists Access for Vehicles Signage Proposed Materials, Aesthetics and Construction Methods SUMMARY OPTIONS TABLE RECOMMENDATIONS APPENDIX A: OUTLINE DETAILS FOR PREFERRED OPTION APPENDIX B: SERVICES SEARCH RESULTS 5016-UA UT31-R-02 i

5 1 INTRODUCTION Hyder Consulting (UK) Ltd was appointed by the Canal and River Trust to carry out a feasibility report to review options for the improving the existing pedestrian ramp adjacent to Prince Albert Bridge, Camden in order to improve ease of use and safety for cyclists and pedestrians. The canal towpath is a popular route used by both cyclists and pedestrians and the existing ramp forms a link from the towpath up onto Prince Albert Road. At present there is a perception that the steepness of the ramp is discouraging cyclists from using it and they are choosing to remain on the towpath heading eastwards into the congested Camden Town area. This report will examine the options for rebuilding the ramp to make it more attractive to cyclists and to enable them to join the highway cycle route adjacent on Prince Albert Rd. There is also an existing stair flight from the Prince Albert Road down to the towpath which is located adjacent to the canal bridge abutment. There is restricted visibility for pedestrians to see cyclists on the towpath as they emerge from under the bridge, and there is little time for cyclists to react. As a result this report will also consider options for relocating the staircase further away from the abutment of the road bridge. 2 CONSTRAINTS & OPPORTUNITIES 2.1 Topographical The existing site comprises a sloped plot of land between the road and the canal. The plan length of the slope varies from between 15m at the existing steps to 23m adjacent to St Mark s Bridge (see sketch below). The length of the plot is approximately 48m. The levels of the footway adjacent to Prince Albert road vary between m at Prince Albert Bridge to m at St Mark s Bridge. The towpath levels through the site vary from m to m. Prince Albert Road Existing steps St Mark s bridge Existing ramp Regents Canal 5016-UA UT31-R-02 1

6 2.2 Existing Pedestrian Ramp The existing pedestrian ramp is approximately 2.0m wide. The overall rise of the ramp is 4.0m and the plan length is 40m, of which 36m is inclined. The resulting average gradient is 1 in 9 (11%) and a maximum gradient of approximately 1 in 7 (14%). There are no intermediate landings. 2.3 Pedestrian Crossing Facilities An existing pedestrian crossing is located on Prince Albert road adjacent to St Mark s Bridge, which provides access to Regent s Park and London Zoo. 2.4 Environment and Heritage The site is located adjacent to the north-east abutment of St. Mark s Bridge, which is a listed heritage structure and the solutions proposed must be separate from this structure. Tarmac Surfacing will not be used for any ramp elements. Trees are present on site however, whilst there are no Tree Preservation Orders (TPOs) in place on the site, the site is within a Conservation Area so it is desirable that the options presented minimise the amount of trees that will need to be removed. In addition, no safety railings may be placed adjacent to the canal at the base of the ramp as they are liable to be used by canal users to tie up their vessels UA UT31-R-02 2

7 2.5 Utilities and Services within the site Details of the services search carried out by Canal and River Trust are included in Appendix B. Two above-ground brickwork service boxes believed to contain Low Voltage (220V) power cables are located within the north-west area of the site at the top of the slope adjacent to St. Mark s Bridge. Two Thames Water manholes are located on the embankment slope adjacent to St Mark s Bridge A High Voltage electric cable is located in a buried duct in the towpath. A gas main is located in the footway of Prince Albert Road 2.6 Improvement in Wayfinding There is currently very little signage for pedestrians and cyclists on the towpath or at street level. This project would give the opportunity to improve wayfinding by providing signage which could also be linked into wider wayfinding projects such as Legible London. 3 REVIEW OF DESIGN STANDARDS When designing ramps for mobility impaired users it is often stated that the ramp should be DDA compliant. In fact the DDA regulations were introduced to ensure that mobility impaired or disabled users are not restricted from using or accessing places and property but it does not specify minimum standards, such as gradients etc., and hence no design can be DDA compliant. A numbers of standards and guidance documents are available to help ensure designs take sufficient account of mobility impaired users. BS8300 is generally quoted when designing ramps and disabled access. However this was primarily aimed for buildings and hence the recommendations can be very onerous when they are applied to outdoor ramps, bridge accesses etc. In this case there are other documents which give guidance more relevant to the design situation. Three main design standards were reviewed in order to prepare preliminary options for this project as follows: BS8300: 2009 including Amendment No (BSI) A Disabled People s Access to the Countryside (DPAC). London Cycling Standards (TfL) A summary of the key design criteria for ramps and stairs is summarised in Table 1 overleaf. The table shows certain design criteria have significant differences depending on which standard is used. For the ramp design options (options 2 and 3) discussed in section 4, generally the recommendations set out in the DPAC were used as this aligns the closest with the design situation. Recommendations in BS8300 were found to be too onerous and it would not be possible to provide a compliant solution with the constraints of this site. The London Cycling Standards do not give recommendations on ramp design but where possible, geometric layout guidance was followed. The DPAC recommendations were treated as minimum standards and where possible these were exceeded as far as was possible UA UT31-R-02 3

8 Design Criteria BS8300: 2009 Disabled People s Access to the Countryside (DPAC) London Cycling Standards Ramp Gradient 1:20 to 1:12 1:20 to 1:12 No guidance Maximum Ramp Going Length Varies between 10m for 1:20 gradient to 2m for a gradient of 1:12 Varies between 15m for 1:20 gradient to 9m for a gradient of 1:12 No guidance Maximum Ramp Rise Length Varies between 500mm for 1:20 gradient to 166mm for a gradient of 1:12 750mm between landings No guidance Ramp bend radii No Guidance No Guidance 15m (Clause 4.5.4) Ramp Width Not less than 1500mm Not less than 1200mm 3.0m recommended 2.0 minimum Ramp Landing length 1500mm 1500mm No guidance Stair Design Going: mm Rise: mm Going: mm Rise: mm No guidance Stair Width mm 1200mm minimum No guidance Ramp Landing length 1500mm minimum 1500mm minimum No guidance Max No. of steps between landings 20 Provide landings to limit height of each flight to 2.0m No guidance Visibility S p l a y s No guidance No guidance X = 2.0m Y = 20m (15mph) Table 1: Summary of Key Design Guidance Key Design criteria considered onerous, or where the topography and land availability will make compliance difficult or impossible. Criteria that are contradictory between standards are highlighted in amber. Design criteria which show a good correlation UA UT31-R-02 4

9 4 R A M P O PTIONS 4.1 Option 1: Refurbishment of Existing Ramp The existing ramp connects the towpath adjacent to St Mark s bridge with the footway adjacent to Prince Albert Bridge. The existing ramp has an average gradient of 11% (1:9) and a maximum gradient of 14% (1:7). The ramp is in a fairly poor condition with the surfacing breaking up in places. There are no existing landings, and the ramp height is 4.0m. In order to comply with the recommendations contained in the DPAC code, the ramp would have to be split up into six ramped lengths with rises of 667mm each, and five intermediate landings would be required. The minimum recommended landing length is 1500mm, so the total landing length required would be 7.5m. The existing ramp length is approximately 36m however this would reduce to 28.5m after deductions for landing lengths and the resulting average gradient would be 1 in 7.1 (14%) This solution would require minor benching into the slope and also localised build-out of the embankments at landing positions, which would require small retaining walls to be built. It is also assumed that the ramp width would remain unchanged. In conclusion, there is nothing that can be done with the existing ramp to improve compliance with standards and to improve usability, other than to provide a cosmetic make-over to improve the ramp aesthetics within the wider context of the site s conservation area status and its proximity to St. Marks Bridge. The foot of the existing stair flight should be relocated approximately 10-11m away from the wing wall of Prince Albert Bridge as this will provide adequate visibility for cyclists emerging from under the bridge. The top landing of the stairs would remain at the end of the bridge parapet. A straight flight of stairs could be constructed in between with one landing at mid height. Each flight would require 11 rises of 177mm and 10 goings of 350mm, with a single 1500mm long landing in between to comply with the requirements of BS8300. To comply with the Disabled People s Access to the Countryside Guide, the stairs in the revised location would require two flights comprising 12 goings of approximately 290mm with 13 rises of 150mm would be required. It is not possible to comply with both this guidance and BS8300 for recommended going lengths and riser heights. Either stair solution would require some minor benching and build-out to accommodate the landing within the existing topography. It is also recommended that the existing entry point from the main road footpath is widened to 2.0m to improve accessibility. No buildability issues are anticipated with this option UA UT31-R-02 5

10 4.2 Option 2: 2m Wide Ramp The only way to accommodate a ramp with a compliant gradient and the requisite number of landings that will comply with standards is by increasing the plan length of the ramp. If the access point from the footway on Prince Albert Road is moved adjacent to St Mark s Bridge by creating a new opening in the metal railings then the overall ramp length can be increased to 68m by creating a path with a single hairpin bend halfway along. This provides a single access/egress point at the top and bottom of the ramp which is favoured by the Highways Authority. An indicative outline of this route, with a 2.0m wide footway is shown in Figure 1 below: New TfL signage Figure 1: 2.0m wide ramp route Allowing for upper and lower landings a minimum of 1.5m long, two intermediate landings of 2.0m at the stair interface, two additional 1.5m long intermediate landings, plus a 3.9m long landing at the hairpin, then the total landing length is 13.9m and the remaining plan length for slopes is 54.1m. If the landings are set with a 1 in 40 fall to aid drainage, then this will account for a total height of 350mm, and the remaining 3850mm of drop from pavement to towpath will give an average slope gradient of 3850/54100 = (7.12%, equivalent to 1:14) This represents a substantial improvement from the gradients attainable with Option 1. A two metre wide path is proposed as this is the minimum width recommended by TfL Standards for combined public / cycle path routes. This standard recommends a bend radius of 15m, which is not attainable within the site boundary. However the achievable radius in this layout is considered to be adequate for the majority of competent cyclists. An added advantage of this option is that if by moving the egress for cyclists close to St Mark s Bridge, cyclists will be able to avail of the existing crossing facilities. These facilities could be upgraded by Camden Borough Council to improve facilities for cyclists wishing to cross over the main road and then cycle along it towards Camden. A new staircase would be located as shown between the first upper and lower intermediate landings as shown in Figure 1. This would be 2.0m wide and will require one intermediate landing UA UT31-R-02 6

11 In order to accommodate the hairpin part of the ramp within the existing slope, some substantial cutting into the slope and build-out will be required and if the existing slope is reprofiled above and below the new footway, the resulting slope gradients will be too steep. Consequently retaining walls will be required on the upper and lower haves of the path leading into and out of the hairpin and pedestrian railings will be needed to prevent falling from height. This option would require the removal/relocation of the brickwork junction box. A two metre wide path has been selected to minimise the height and extent of retaining walls and also minimises required tree removal. 4.3 Option 3: 3m Wide Ramp This option is similar to Option 2 described however the width of the footway has been increased to 3.0m. (Figure 2) New TfL signage Figure 2: 3.0m wide ramp route The proposed alignment has the same path length and gradients as Option 2. The key difference is that in order to build this option, more cutting will be required into the existing slope and more build out will be required on top of the existing slope to achieve the width, particularly at the hairpin bend. Consequently retaining walls will be required on the upper and lower halves of the path leading into and out of the hairpin and pedestrian railings will be needed to prevent falling from height. The retaining wall structures will be more pronounced and will have a greater visual impact on the site compared to Option 2. It will not be possible to position the layout of the route to avoid trees due to the increased width, particularly on the upper ramp and so the main ramp lengths are straight UA UT31-R-02 7

12 This option would require the removal/relocation of the both junction boxes. A new staircase would be located as shown between the first upper and lower intermediate landings as shown in Figure 1. This would be 2.0m wide and will require one intermediate landing. 4.4 Option 4: Do Nothing Option The existing ramp has a maximum gradient of 14% (1:7) and is 2.0m wide. The surfacing is worn and cracked in places. The top of the ramp is adjacent to Prince Albert Bridge and the opening onto the footpath is 1.2m wide between the railings and the bridge parapet. This narrow opening presents a restriction to pedestrians and cyclists at the top of the ramp. Wayfinding for pedestrians and cyclists is also poor. The exit at the top of the ramp is directly onto the footpath of Prince Albert Road and cyclists heading toward Camden will generally cross the road at this point rather than use the existing pedestrian crossing approximately 25m to the west. It is possible that some minor widening of the opening at the footway fence would improve access to the ramp. Some minor resurfacing work at the top of the ramp would also be required. 5 Other Considerations 5.1 Access for Cyclists A key objective of the project is to encourage cyclists heading east along the towpath to utilise an improved towpath ramp to join the cycle route on Prince Albert Rd in order to travel towards Camden Town. The pedestrian crossing adjacent to St Mark s Bridge would benefit from upgrades in accordance with the London Cycling Design Standards Document if Option 2 or Option 3 is implemented. The crossing and approaches will need to be formally assessed and a suitable arrangement developed. Camden have indicated that ideally they would like to convert the footway between St Marks Bridge and the ramp exit to shared use and delineate with corduroy tactile paving. Additionally a drop kerb would be installed to allow cyclists to access the pavement area. In the longer term either a toucan upgrade would be considered or an entire remodel of the junction. The public footway and crossing areas are outside the site and any improvements are envisaged to be carried out by Camden Council. 5.2 Access for Vehicles Access for vehicles is not considered necessary and will be impossible to achieve due to the hairpin bends on Options 2 & 3. The provision of bollards (possibly removable) should be considered to restrict unauthorised vehicular access UA UT31-R-02 8

13 5.2.1 Signage Encouraging use of the ramp is a major element of this project and signage will be a very important factor in achieving this. The TfL Legible London scheme has recommendations for signage and it is envisaged that a minilith outer type sign would be provided close to the bottom landing of the ramp indicating an alternative cycle route into Camden along borough roads Proposed Materials, Aesthetics and Construction Methods Options 2 and 3 will require the construction of retaining walls to support the revised ramp alignment. The shape of the walls will require significant detailing because the base profile will need to be stepped to allow for the gradient of the ramp and the top of wall will be inclined at its interface with the re-profiled slope. In addition a guardrail will be required to the top of retaining walls to prevent falls. In order to construct the complex wall shapes it is recommended that the retaining walls are built with insitu reinforced concrete. If brickwork cladding is used to finish the front face of the wall, the top courses will need to be cut and dressed to suit the inclined profile of the stringcourse, which will follow the profile of the ramp. It is therefore recommended that a patterned profile concrete finish is adopted for the wall faces, and the upper stringcourse section is given a high-quality plain faced finish. We would consider that a patterned profile rebate finish to concrete faces would resemble normal highway infrastructure, and that a carefully selected pattern profile formwork liner, such as those supplied by Reckli Ltd, should be applied to provide a high-quality finish. Carefully selected climbing plants could be used to disguise the lower sections of the retaining wall. Some over-excavation into the existing slope will be required typically with a temporary cut slope of 1 in 1.5 in order to build the retailing walls, which will then be backfilled with structural grade backfill to the finished profile. The construction of the upper retaining wall adjacent to the footway will likely require temporary sheet piling to support the excavations during construction, because a temporary cut slope will likely undermine the footway. It is assumed that construction will commence at the base of the slope, with the upper sections being built last. Options 2 & 3 are rated equal in this regard, however Option 3 may require the use of sheet piling to support the temporary excavations since this option requires more benching into the existing slope than Option 2. It is assumed that ground conditions will be favourable, however a site investigation within the works will be needed in order to carry out a preliminary design and to prepare a detailed cost estimate. We would recommend that black handrails are fitted on to the retaining walls and that the chosen style is complimentary to the existing railings in place on the footway. In addition handrails should be provided for users so that there is always a handrail on at least one side of the ramp. Tarmac surfacing is not considered desirable in this location however we would recommend a bituminous path construction with a buff coloured anti-skid surface dressing. If this is not acceptable then options for paving the ramp include precast concrete flags or block paving, which are both already in use on the towpath UA UT31-R-02 9

14 The stairs could be built with concrete brick or block risers with precast concrete flagging used to form the goings and edgings. Corduroy blister pavings will be required at all landing positions on the stair flights. The ramp is not currently lit at night but it is understood that there is a certain amount of spill light from the adjacent road. It is recommended that in detailed design an assessment of the ramp is carried out to determine if lighting is required and if to what specification. Access for construction plant and vehicles is envisaged to be primarily by road. Temporary lane and footpath closures may be required for this and will need to be approved by Camden. There is limited scope for water based plant/deliveries however the towpath is weight limited to 1.5 tonnes which will restrict options UA UT31-R-02 10

15 Prince Albert Road Cycle Ramp, Camden - Feasibility Report 6 SUMMARY OPTIONS TABLE Option Construction Cost 1 To be advised by CRT Term Contractor Risks Buildability Maintenance Environment & Heritage Planning Cyclist/pedestrian collision Non-compliant gradients. No construction issues expected from improvements to footway and from relocating the stair flight. Anti-skid surfacing will require replacement. Proposed surfacing to be approved by stakeholders. Planning approval may not be required as the works could be considered to be routine maintenance. 2 Approximately 245k construction cost. 3 Approximately 265k construction cost. 4 No capital costs involved unless minor improvement works are undertaken. Cyclist/pedestrian collision Cyclist/pedestrian collision Cyclist/pedestrian collision Non-compliant gradients. The upper retaining wall excavation will require sheet piled temporary works. Access for construction plant will be limited and may require lane closures. The upper retaining wall excavation will require sheet piled temporary works. Access for construction plant will be limited and may require lane closures. No construction issues expected from improvements to footway access width. Anti-skid surfacing will require replacement. Handrails will require repainting. Graffiti removal from concrete surfaces Anti-skid surfacing will require replacement. Handrails will require repainting. Graffiti removal from concrete surfaces Anti-skid surfacing will require replacement. Proposed surfacing and concrete finish to be approved by stakeholders. Proposed surfacing and concrete finish to be approved by stakeholders. Proposed minor improvements to be approved by stakeholders. Planning approval will be required for this option. Planning approval will be required for this option. Planning approval may not be required as the works could be considered to be routine maintenance UA UT31-R-02 11

16 Prince Albert Road Cycle Ramp, Camden - Feasibility Report 7 RECOMMENDATIONS Option 1 does not provide any immediate benefits other than cosmetic over and above Option 4 (do nothing). Neither option provides a satisfactory solution to the issue of encouraging cyclists to use the ramp. Option 3 will provide a better experience for users due to the increased width compared to Option 2, however, Option 3 will require more extensive earthworks and tree removal than Option 2. Since there are no Tree Preservation Orders within the site, Option 3 is preferable. The retaining walls for Option 3 will be bigger and potentially more visually intrusive than the retaining walls for Option 2, however, if the wall finishes and slope landscaping are carefully considered and developed in sympathy with the adjoining built environment, then there is an opportunity to enhance the appearance and amenity value of the site. We would therefore recommend that Option 3 is developed to detailed design UA UT31-R-02 12

17 APPENDIX A OUTLINE DETAILS FOR PREFERRED OPTION SKETCH NUMBER S001-UA003174

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19 APPENDIX B SERVICES SEARCH RESULTS

20 British Waterways Hyder Consulting (UK) Limited Professional Services Contract 2011 to 2014 Task Brief Utilities Survey o:\bids and prequals 2011\british waterways tasks\prince albert road cycle ramp\client brief\prince albert road ramp design brief.docx, page 14 of 15, 09/12/2011

21 British Waterways Hyder Consulting (UK) Limited Professional Services Contract 2011 to 2014 Task Brief o:\bids and prequals 2011\british waterways tasks\prince albert road cycle ramp\client brief\prince albert road ramp design brief.docx, page 15 of 15, 09/12/2011