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Auckland - Te Ara Ki Uta Ki Tai (gradient design of shared path)

Auckland Transport and Waka Kotahi NZ Transport Agency are creating a 7 km long shared path, mostly 4 m wide, from Glen Innes to Tamaki Drive alongside the Eastern Railway Line in Auckland. The project will be delivered in four stages, and stage 1 was officially opened on 9 December 2016.

The topography is undulating, with some of the path sections reasonably steep. The longest continuous ramp is just over 650 m long where the gradient is 8.3% (ie a gradient of 1:12, which is considered the maximum permissible in various guidance documents). The design approach was to create an “accessible route” that is usable by people with disabilities. The parameters for this are defined in NZS 4121:2001 – Design for Access and Mobility – Buildings and Associated Facilities. This Standard applies to structures, rather than paths following natural terrain and so it was not essential to follow the standard in this case. This standard however should be applied where a ramp leaves a bridge for example (unless an alternative solution is granted as part of the Building Code process).  Applying this standard to a pathway resulted in landings approximately every 9 metres. The landings were 1.2 metres long, less than the wheelbase of a standard bicycle, and they had a destabilising effect.

After the opening of stage 1, concerns were raised by people cycling that undulations formed by level landings make the path uncomfortable, and possibly unsafe. A further challenge is that the horizontal landings are very subtle and can hardly be seen looking along the path (see video below).

Glen Innes pathway (video: Jon Ashford, ViaStrada).

But when riding the path in a downhill direction, this becomes uncomfortable when speeds exceed about 20 km/h, and at some point, a bike may become unstable. Some users have thus rejected the path and continue to commute on the parallel road network, defeating the purpose of building a pathway in the first instance.

Auckland Transport does not want to repeat the design approach for subsequent project stages and sought advice on this issue from various consultants and accessibility advisors.

Project owner: Auckland Transport (stage 1)

 

  • Key challenges and issues
    • How to provide a steep but accessible path without making it uncomfortable or unsafe for people cycling.
    • How to retrofit stage 1 of the project so that safety and usability concerns are addressed.
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  • Successes and learnings

    In an external technical report, two alternative design approaches were discussed. The first alternative suggests that path users should be segregated, at least on the steeper sections. That way, the cycling-part of the facility can be provided without horizontal landings. On the less steep sections the landings are not as disruptive, as they are spaced further apart, and thus can be installed full-width.

    The second design alternative would see horizontal landings built adjacent to the path. That way, users who desire to have a rest can pull off the main path, which can thus be built without horizontal landings in the trajectory of people cycling. Note that this does require slightly steeper short lengths of connecting path (10% gradient approx.).

    There were a variety of options available for remedial work on the section that has already been built. Above 6% gradient, the pathway could be rebuilt, applying one of the alternative designs above. Obviously, this would be quite costly.

    As the safety issue is related to the frequency of the rest platforms, intermittent removal of rest platforms and replacement with a single gradient may address the problem. It is difficult to assess if the removal of alternate platforms will be sufficient to address the safety issue or whether two consecutive platforms should be removed. Hence field trials would be necessary involving local cycling and disability users to ensure the safety issue for people cycling has been addressed and that mobility requirements are still met. Off-path rest areas (possibly pre-cast) as shown above could be installed where platforms have been removed. The following section view demonstrates how such a remedial measure could look.

    All of the above options have their respective merits. Auckland Transport carried out consultation with a range of stakeholders (including Bike Auckland and Be Accessible) and determined the following remedial works were required to ensure the path could meet the objectives and is safe for all ages and abilities:

    • Remove 49 platforms and replace approximately 440m of path. The path is to be replaced in 45–70m sections at 1:12 (approximately).
    • Retain of 34 platforms and 960m of path.
    • Construct eight new 3m long platforms on the path with a 3x3m rest area adjacent (off path) – junctions to have a 10m vertical curve.
    • Highlight remaining platforms, i.e. acid etched or similar to provide texture contrast (not painted).
    • Construct a level platform from the path to the lookout.

    The sections of path and associated platforms were identified for removal where they present a higher safety risk to cyclists and/or are considered to adversely affect mobility access. The focus for remedial works is where the path is steep and has a curved horizontal alignment, where cyclist speed is an issue, where platforms are poorly constructed, and on long continuous grades that limit use to able-bodied pedestrians.

    It was considered that adding signage and contrasting surfaces alone at the platforms would only partly reduce the risk and was not recommended.  There were also recommendations for improvements, regardless of whether the full remedial package went ahead, including removal of obstructions, providing user behaviour markings, increased maintenance so plants were not overhanging the path, and additional wayfinding and seating.

    In moving forward to the delivery of further stages, the primary lesson that was learnt from Phase 1 was that it would be better to provide separate paths for pedestrians and cyclists. This is particularly important where it is not feasible to manage cyclist speeds on downhill grades.

    Where a combined path is unavoidable, landings will be included as per the specification below:

    Gradients

    Use 

    Max. gradient    Preferred max. length

     

     

    Cycles only

    3% (1:33)

    No limit

    5% (1:20)

    240m (maximum)

    8.33% (1:12)

    90m (maximum)

    10%

    30m (maximum)

    12.5%

    15m

     

     

    Combined Cycle
    and pedestrian paths

    3% (1:33)

    No limit

    5% (1:20)

    120m (between landings)

    8.33% (1:12)

    45m (between landings)

    10%

    9m (between landings)

    12.5%

    3m (between landings)

    Landings/rest areas

    2%

    3 m (minimum)*

    Interpolation between values is permitted.
    *3 m landing excludes a 2 m length of a transition curve at each end

    Source: Table 10 of the Auckland Transport TDM Engineering Design Code(external link)

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