E&T spoke to the engineers behind the lighting architecture across London’s recently opened Elizabeth line which aims to promote a safe and efficient passenger experience. Using LEDs to light up the stations, escalator shafts and concourses of the Elizabeth line was a bold move from Transport for London; especially as when they decided on its use back in the late 2000s, LED technology was yet to break into the lighting world.
But this did not stop Paul Kerrigan, the lead electrical engineer responsible for Crossrail’s line-wide lighting solutions and uninterruptible power supply, and his team from taking the plunge to make this a reality. In fact, the Elizabeth line is one of the first sub-surface infrastructure projects to be lit entirely by LEDs, and the decision to use the technology was based on industry evidence that its use will help reduce energy consumption and maintenance requirements.
“We decided on its use during the very early development stages of LED technology. We had prototyped none of the designs then – it was purely artistic impressions and drawings of the concept,” Kerrigan tells E&T. “So, when it came round to design, we had to embrace the growing technology to develop the products.”
The new line traverses the capital, from east to west, with its entire central section – from Liverpool Street to Paddington – lying underground. The Crossrail team said the route made lighting design critical, not only for passenger safety but also for enhancing their experience within the subterranean environment. “The general use of indirect lighting within the concourses, escalator tunnels and platforms emphasises the spatial envelope rather than drawing attention to the luminaires themselves,” Kerrigan explains.
As a result, the Crossrail team used the light-grey, matt-textured, glass-reinforced concrete lining of the station and escalator tunnels to reflect light onto the passenger areas. This helps “create a sense of spaciousness within the underground environment”, according to Kerrigan.
Specialist LED lighting designer and manufacturer Future Designs created three bespoke lighting solutions that passengers will experience across the line: the Ikon uplighter, Ikon Emergency luminaire and the Plinth luminaire. David Clements, chief executive of Future Designs, explains its LED technology is “ultra-powerful” and will reduce the whole-life cost of the project.
Future Designs’ Ikon products sit on the wayfinding totems, which incorporate the company’s emergency lighting. It is an uplight designed to illuminate the area via reflection from the curved ceiling. It also incorporates emergency lighting, fire alarms and public help points.
“All the lighting on those totems, which is the only light source in that area, was a conceptual design that David developed,” Kerrigan explains. “And its process from concept to the end product flourished over time to what you see [on the line] today.”
LIGHT DESIGN
The Totem
The totem is the primary source of lighting in the station lower concourse; it combines wayfinding signage with the top section comprising a high-powered LED uplighter. The totem also houses six emergency lighting units located at various points both vertically and horizontally on the totem body. The team spaced such totems at 9m intervals, illuminating a tunnel area of 8.1m in diameter.
The luminaire provides uplighting onto the GRC wall and ceiling cladding material and distributes a consistent lighting level onto the floor surface, providing horizontal and vertical illuminance of 150 lux and 0.5Uo (uniformity). The top section of the luminaire is constructed from aluminium and acts as a passive heat sink, which controls the ambient operating temperature of the LED units (limiting them to 35°C) to maintain and prolong the life of the LEDs while also acting as a distinctive architectural feature.
The Crossrail team incorporated glass-laminated micro louvre into the totems located nearest to the base of escalators, to mitigate any direction glare that could be seen by passengers. They designed the totem for the subsurface environment, meeting the same requirements as the platform lights.