This article was originally published in the February 2024 Issue of Bridge Design & Engineering. 

Speaking with lighting design firm HLB, José Sánchez de Muniáin explores the development of modern dynamic lighting for bridge projects and its potential to transform surrounding communities.

For a budget-conscious sector where advancements in technology can take decades before they cease to be considered new, the speed with which the advent of LED technology and computer controlled systems have transformed the nighttime bridge landscape is quite astonishing. In what feels like no time at all, dynamic lighting systems appear to have become de rigueur for any class of signature bridge or cherished historical crossing.

Today, at the touch of a button, operators can change the colours of their bridge, introduce sequences and even alter light intensity in different sections, lifting the structure to new levels of social media/TV-friendly nighttime beauty. And, more importantly, they enable the structure to actively reflect the character and the feelings of the community it serves, be it marking a local celebrity’s life, a sporting victory, an historical event, or a significant date of the year.

It is difficult to believe that it was only 10-15 years ago that bridge lighting systems mainly consisted of high-intensity discharge lamps, technology that was the complete opposite to the LED systems of today: “They were massive in their scale and they didn’t dim or change colour,” remembers Ken Douglas, senior principal in the New York City office of HLB Lighting Design. “So anytime you wanted to change colour, it was literally a manual process and somebody would have to go out and put a lens in front of it to change the colour.” Then came the LED revolution: “When we first started doing this work, we had to talk the owners and operators into doing it because it was like, ‘Why do I want to do that?’ And now it shows up in the RFP [request for proposal]. It’s a requirement because people have seen it, they understand what’s happening, and they want it for their community.” Such systems are becoming so popular that they are even creating a new service sector: “There are enough density of dynamic lighting systems in the world that vendors are coming together who want to manage them for you. All these different bridge projects – and not just bridges – they all have a computer in the closet someplace and somebody needs to manage them.”

That a ‘good’ lighting system is not defined by the technology behind it is a point that Elizabeth Johnson, associate director at HLB, is keen to highlight: she explains that aesthetic success is based on how far the system has aligned with the characteristics of the surrounding community: It is why the word ‘context’ features strongly in all lighting bridge projects, driving the ultimate resolution. “It requires a lot of listening to the stakeholders,” adds Douglas, “We want to understand the structure, the environment, and the community. Is there any history at that location that we should be aware of, either political or geographical? Had a bridge existed there before that had a very particular persona that people were attached to? These structures become symbols of their community and people get very emotionally involved with them.”

As an example, they point to a pro-bono project that HLB is currently working on in the city of Selma in Alabama, around 250km south-west of Atlanta. Named after a former Confederate brigadier general and leader of the Alabama Ku Klux Klan, in 1965 the Edmund Pettus Bridge was the site of a bloody civil rights conflict that resulted in over 50 protestors needing treatment for injuries inflicted by the police. The historical importance of what become known as Bloody Sunday has been commemorated on the bridge throughout the years, including in 1996 when the Summer Olympic torch relay crossed the bridge, and more recently in 2015 when US president Barack Obama delivered a speech on the conflict’s 50th anniversary.

The 380m-long crossing comprises a steel through arch main span 76m in length and side spans consisting of concrete arches. Around three years ago, the community in this small southern town approached HLB for assistance in marking the importance of the structure in US history. “It is a location that is economically depressed where most of the shops are empty. People do come to see the structure because of its history, but they get out of their car, take a picture, and then leave again. And one of the things the city would like is to have the bridge act as an economic driver as well as a symbol of pride for the community,” explains Douglas.

While the project is still in its infancy, word has got around and positive impacts are already making themselves felt. “People are buying empty storefronts and buildings nearby, so there are the beginnings of some economic activity, which the mayor and the city council are very excited about,” says Douglas. If all goes to plan, HLB hopes that in the next 12-18 months the dream will become reality. “For me, projects like this, where it is the community that wants to light a bridge, are the most rewarding,” says Johnson. “The feedback is really special and I would recommend to any community with a beautiful arch, truss, or even a beautiful girder, to think about adding some light to it, if it is an important place.”

In contrast to retrofits, new-build projects afford lighting designers the opportunity to influence the design of a bridge so that its nighttime impact is optimized. As such, HLB is normally engaged at the beginning of a bridge project, as part of the design-build team bidding for the contract: “And that’s because our work really needs to be heavily integrated with the other systems. So to a large extent we collaborate with the architecture team, particularly on the form of the bridge. We often have conversations about materiality, about structural shapes for an arch or for a pier on a cable-stayed bridge, where slight changes in those structures or the adding of a little reveal line in the concrete gives us something to highlight at night that would be different if it wasn’t there,” says Douglas. The skill of the lighting designer, he adds, comes in matching the context derived from the community with the aesthetic vision of the bridge designer: “There are big gestures that you can make as a bridge architect, but there are also really subtle ones that can make the difference between a great structure and an amazing structure. And when we get to add a layer of aesthetic lighting, sometimes you can really bring those out.” As an example, he highlights the Iowa-Illinois Memorial Bridge carrying the I-74 over the Mississippi River. The bridge features striking basket-handle twin through-arches, but it is not just these that are lit up at night: “The piers are actually very interesting – they are not completely flat, they overlap, and when you light them at night you get to see a different part of the architecture that maybe you didn’t notice during the day.”

In contrast with the historical context of the Edmund Pettus Bridge and the Mississippi River environment of the Iowa-Illinois Bridge landmark, HLB is currently working on an unusual structure where the challenge for the bridge lighting system is very different. Here, the structure is in conversation with the bright lights of downtown Miami.

The I-395 is a monumental structure that features twin cast-in place box girders suspended by stay cables attached to six arches that spring from a central pier between the two decks. It is currently under construction and scheduled to complete in 2027.

The new iconic structure, whose highest arch is 99m above ground, will span two busy roadways as well as a planned 30-acres of public gathering space. It is designed to improve mobility at a key corridor for traffic headed to the Port of Miami, MacArthur Causeway and Miami Beach. “It’s an interesting challenge because there is so much light in the middle of downtown Miami already, and now there’s going to be this signature bridge. It is about how you integrate into this downtown urban environment with an iconic bridge surrounded by condos” says Douglas.

The approach to the Fountain Bridge has to be balanced by a variety of considerations: the need to ensure that the structure is bright enough to be noticed in an already illuminated urban environment, but not too bright that it detracts from the self-same surroundings and, at the same time, annoy the neighbours: “That’s where controllability will come into play. The fact that we can dim things, change the output over the course of the evening. Perhaps the structure wants to be brighter from 7pm to 9pm, and then dimmer between 10pm and 12pm, and then dim until 3am, when it goes off. We’ve got the ability to control all that just from the computer,” points out Douglas. This approach can even be taken section by section depending on the bridge elements’ location. “For Champlain Bridge in Montreal, the multi-kilometre long edge girder was lit but, for sections through a neighbourhood, the output was set to run at 30%.”

And being a good bridge neighbour isn’t just restricted to human habitation. Another major influencing factor that needs considering at an early stage of the lighting design is the local wildlife identified in the environmental impact report. “Those animals are typically addressed with light intensity and colour controls, depending on what species of creature we’re trying to be respectful of,” explains Johnson: “For example, certain colour temperatures may pull in night-migrating birds. There are a few things that have been well known for a long time, especially turtles and amber light and nesting, but other elements we just keep looking out for and combing through papers. This is a blossoming field of science because all animals are different. We also rely on the environmental team on the project, which almost always has a biologist,” she adds.

At an early stage of a project, the light designer begins to make 3D models of the bridge in order to test different ideas. BIM is not the exclusive remit of bridge designers and, in fact, similarly to engineers and architects, light designers used to often also test their lighting set-ups on cardboard models. “But now we can fly through the real structure in the computer. We can get different angles. We can see what the driver sees, we can see what somebody a mile away will see. So we have a really good understanding of what’s going to happen there,” says Douglas.

Using the specialist software, it is possible to place light fixtures on the bridge, input the measurements of the light distribution, and click a button: “After hours of the computer churning away, we’ll get an image that is of the lit structure, and it is very faithful to real life,” says Douglas. The resulting data, which can relate to the precise aim of adjustable lights, then feeds into the contract documents.

As things stand today, the modern dynamic lighting system is accompanied by a management software tool that is configured for the particular bridge. “It is sort of like buying an iPhone – it doesn’t have any content when you get it, and then you have to develop the content to play for different events. Part of our deliverables is to make sure that when the bridge opens, the owner has a good selection of scenes that reflect their community and their priorities,” says Douglas. And, if lighting technology continues to develop apace, it is highly likely that in the next few years the range of lighting options will increase markedly. “The evolution will be around more direct-view light sources as opposed to the current scenario where users are seeing the light reflected off a surface. And that technology is now advancing to be more robust, more capable of living in these kinds of environments,” says Douglas. Furthermore, it is likely that moving fixtures will also soon become an option for owners: “When you go to a music concert you see the light fixtures moving around – doing that is very hard to do outdoors because the equipment just isn’t robust enough to be in the rain and the cold. But there is technology that’s moving the world towards that potential and the design possibilities it opens up.”