LDP was engaged by Auckland Transport to provide lighting design services for underground rail platforms in the Britomart Transport Centre (BTC), a major transportation hub in Auckland’s CBD. The existing lighting scheme for the BTC platforms consisted of an array of overhead recessed metal halide projectors installed in portholes above the electrified train power supply rails, which due to access difficulties and short lamp life led to regular reductions of light levels on the platforms. In addition, new lighting standards commissioned for the construction of the City Rail Link meant the light levels at time of original design and construction of the BTC were insufficient for its safe and efficient future use.
The BTC platforms existing array of overhead metal halide projectors were prone to performance and access difficulties including:
- High compliance sensitivity to single lighting point failure – due to the centre platform being illuminated fundamentally by the narrow beam “spotlights” in the overhead portholes, with little overlap or supplementary contribution from neighbouring fittings to a particular platform area, failure of a single overhead light creates a high risk of a non-compliant dark spot on the platform;
- High criticality on luminaire aiming and orientation – as an aimed system, any changes to luminaire orientation or mounting (potentially inadvertently via maintenance work by other trades in the busy behind-mesh ceiling space) which affects a “spotlight” aim point risks creating non-compliance at platform level;
- High & varied luminaire inventory – many individual luminaires of varying makes, models, wattages etc to keep inventory for and maintain;
- Access difficulties – access to the lights in the overhead portholes is onerous, requiring a shutdown of the 25kV OLE and the use of a specialist track-based Kiwirail-owned elevated work platform which is rarely available and based in Wellington, resulting in long delays to being able to access the fittings for maintenance;
- Regular lamp failures – metal halide lamps have a short lifetime and reduce in output quickly, meaning lamp replacement is regularly required;
- Architectural complexity – the lighting system in the cavern is heavily reliant on reflection from the stainless steel ceiling mesh to achieve a well-lit scheme, however the mesh has attracted dust and grime and its reflective properties have reduced over time. The porosity of the mesh also reduces the effective surface area for reflecting uplight to platform and viewer level. The side porthole lighting is almost exclusively delivering an uplight effect to the mesh to ensure the station presents an appealing view and does not take on a dull appearance, and which is easier to maintain than the lighting in the overhead portholes as they are accessible from a standard scissor lift MEWP;
- Mounting locations – a replacement lighting system is realistically and aesthetically confined to installation in the existing portholes, restricting design options;
- Porthole size – portholes measure 600mm diameter, limiting the size of potential replacement luminaires;
- Porthole obstruction – CCTV cameras on suspended rods occupy several portholes;
- Above-mesh clutter/obstruction – difficulty working in ceiling space due to above mesh clutter and thick concrete beams between lighting bays limits the technicality of the lighting solution proposed, both in the physical space that can be occupied by the lighting apparatus above a porthole and in its means to effectively network with other lights;
- Site complexity – the Britomart cavern is a complex, undulating space where typical outdoor infrastructure lighting approaches are insufficient.
These issues resulted in persistent difficulties undertaking lighting system maintenance and ongoing lighting non-compliance on the central platforms.
Britomart - prior to LDP undertaking the project
LDP provided a lighting design which met all requirements of the brief.
The LDP Approach
The LDP lighting design approach for the Britomart platform area has therefore been developed to overcome the noted challenges, deliver lighting levels compliant with agreed standards, and preserve the appealing views of the station interior by way of:
- New direct lighting using suspended hi-bay LED luminaires in the overhead portholes to provide overlapping general area illumination at platform level to achieve lighting compliance target levels
- Preservation of the existing side porthole indirect lighting, to lift the background luminance in the cavern space, thereby reducing glare, and providing for ongoing amenity views of the cavern.
To achieve this, the interior cavern space was mapped out with state-of-the-art terrestrial laser scanning point cloud survey equipment (millions of points were captured) and imported into proprietary 3D lighting design software, allowing for a high accuracy design environment of a complex undulating space to be generated with confidence and for potential lighting solutions to be tested. Due to the geometric complexity of the site (unique ceiling shape, curved surfaces, walls, floors, multiples obstacles such as signage, billboards, gates, columns), the 3D laser scanning was the only way to reduce the unknowns and ensure that LDP were designing in the most accurate 3D environment possible. Without the detail obtained through the scanning process, any inaccuracy could have resulted in lighting non-compliances and thus failing one of the main purpose of the project (i.e. AT-TDM and DDO compliance). Non-compliance may have resulted in major financial consequences (new design require, new luminaires, etc.). So the design had to be pin-point right and accurate.
The selected solution replaced the outdated projectors with an array of high-bay LED luminaires which fit snugly through the overhead portholes, resulting in a cost-effective, high performing, low-maintenance solution.
Benefits of the new installation include greatly increased light levels on the platforms, compliance with incoming lighting standards without overlighting, greatly reduced energy use, improved uniformity, enhanced resilience, thanks to overlapping contribution from adjacent fittings at platform level, minimisation of risk to workers associated with lamp maintenance, 10 year warranty on all luminaires, and flexibility for future light output increases should standards or patronage changes require.