TBM: Tunnel Business Magazine asked Michael N. Maltezos, Transportation Sales Manager for Kenall, about the trends he is seeing concerning tunnel lighting.
There is certainly no argument that LED lighting systems have established a strong foothold in the lighting marketplace over the last several years. The transportation industry is no exception, with new LED cobra head-style luminaires replacing traditional HID cobra head luminaires on our roadways and new linear LED light fixtures replacing conventional linear fluorescent fixtures in our rail transit facilities.
However, LED technology has taken a while longer to penetrate the very specific market of vehicular tunnel lighting in North America. Although both the New York/New Jersey Holland and Lincoln Tunnels have recently been retrofitted with LED lighting, and an LED Lighting RFP is currently out for Boston’s Central Artery Tunnels, very few tunnels in North America to date have been illuminated with LED light fixtures. This is largely because cost-effective LED lighting that met our stringent tunnel lighting standards was, until recently, simply unattainable. With rapid advances in LED technology over recent years, however, owners and specifiers of North American tunnel lighting projects are finally adopting LED lighting systems as the norm.
Until recently, in terms of light sources, the most common options for tunnel lighting owners were fluorescent and/or high pressure sodium (HPS) luminaires. Fluorescent sources were typically utilized in the Interior Zones of the tunnel, where lower light levels are required; they were also used in Nighttime and Emergency Lighting Fixtures, in all tunnel zones. Fluorescent sources typically have good color rendering and energy characteristics, but do not last as long as HPS sources; further, fluorescent sources lack the lumen output “punch” that is required for fixtures in the Threshold Zones, in which very high light levels are required to ease the adaptation of the drivers’ eyes as they enter the tunnel portal from bright sunlight. As such, HPS sources have typically been used in tunnel Threshold Zones and Transition Zones, to provide a greater lumen output (punch) per fixture; i.e., a bigger bang for the buck.
In some cases, HPS fixtures have even been utilized throughout all tunnel zones as an overall “optimized” solution. Until recently, LED tunnel luminaires did not have enough output – either in a cost-effective manner or at all – to justify using them in the Threshold Zone. However, with the latest improvements in LED technology and LED tunnel luminaires, higher output LED fixtures for the Threshold Zone are now a realistic option.
Fast-forward to today … LED efficacies have increased substantially, and yet power consumption has been held constant. An example is as follows:
Recent 300-W Nominal, 5,000K IES Type II Short LED Tunnel Fixture: 27,000+/- lm (Initial Delivered) driven @ 1050 mA; 309 watts actual power consumption
Latest 300-W Nominal, 5,000K IES Type II Short LED Tunnel Fixture: 35,000+/- lm (Initial Delivered) driven @ 1050 mA; 309 watts actual power consumption
For purposes of comparison, the following example is given for a traditional 400-W HPS tunnel fixture:
Recent 400-W Nominal, 2,200K IES Type II Short HPS Tunnel Fixture: 35,000+/- lm (Initial Delivered, 70% Fixture Efficiency); with HPS CWA ballast, 464 watts actual power consumption
With energy-efficient LED lighting now effectively meeting or exceeding established tunnel lighting technologies, there is now a substantial enough increase in the efficiency of LED lighting design and related savings that can be realized while simultaneously meeting our tunnel lighting design standards. DOTs use recommended lighting practices and guidelines for highway lighting, which include specific criteria for tunnels, set by either the Illuminating Engineering Society of North America (IESNA) or the American Association of State Highway and Transportation Officials (AASHTO). However, both IES and AASHTO point out that these recommended practices and guidelines are not a mandate, and DOTs are free to make their own decisions about lighting criteria.
Accordingly, effectively illuminating tunnels is often times a challenge; still the vast majority of North American tunnel lighting designs are done to IESNA Recommended Practice RP-22.
One of the biggest misconceptions is that tunnel lighting design is based on the metric of “luminance,” which in this particular application is the total amount of luminous flux perceived by the driver as reflected off the various tunnel surfaces, at a particular angle, at a fixed distance. Luminance for tunnel lighting is calculated and measured in cd per sq meter. This is in direct contrast with most conventional roadway lighting designs, which are based on “illuminance,” which is the amount of luminous flux incident on a flat surface. Illuminance is typically calculated and measured in lux or footcandles (fc). The metric of luminance far better correlates to the needs of drivers in a tunnel and to the fact that drivers’ visual perceptions are vital and must be properly maintained while traveling through the tunnel. Still, many owners and designers who do not frequently deal with tunnel lighting often do not understand the differences between luminance and illuminance, and the impacts they will have upon a proper tunnel lighting design. I believe it is really incumbent upon experienced tunnel lighting designers and manufacturers to educate owners and engineers on all the nuances of responsible tunnel lighting before a project begins, so the proper tunnel lighting design criteria can be developed. Kenall actually performs several tunnel lighting seminars around the country each year, to educate owners, designers, engineers and contractors in the art and science of good tunnel lighting design and maintenance.
Actually, no two tunnel projects are the same; in fact, every tunnel project I have been involved with has had its own set of distinct differences and challenges. Most recently, Kenall provided the new LED tunnel luminaires for the Brooklyn Battery Tunnel in New York City. This project was a retrofit due to Superstorm Sandy and, as a result, was filled with numerous issues and challenges. The existing luminaires were recessed in the tunnel ceiling, in 30-in. long x 24-in. wide x 10-in. deep box-outs in the ceiling concrete. Accordingly, the new LED tunnel luminaires had to be located in these same existing ceiling box-outs. This presented a host of issues including: physically fitting the tunnel fixtures into the box-outs while still leaving enough room for installing/maintaining personnel to fit their hands inside the box-outs to perform work; having all the luminaires perform as intended without overheating (i.e., pass a stringent heat test inside the ceiling box-outs), especially in the Threshold Zone where lumen outputs are particularly high; designing and fabricating fixture mounting brackets that would fit the existing luminaires’ anchor bolt mounting pattern; and many more. In short, the answer turned out to be Kenall manufacturing a custom-designed fixture to accommodate all of the challenges and design requirements for the project.
The market is most definitely growing. Some of this growth is generally due to our aging infrastructure, in which outdated or improperly functioning existing tunnel systems are now in dire need of replacement. Some of the growth is due to increasing capacity needs for our public roads and highways, and the related reality that DOTs have run out of right-of-way acquisition space in urban areas, resulting in the need to go “under” rather than “around,” when re-constructing a major interchange. Some of the market growth is due to anomalies and/or natural disasters, such as Superstorm Sandy a few years ago, leading to major reconstruction work such as in the Brooklyn Battery and Queens Midtown Tunnels in New York City.
Michael N. Maltezos, MIES, is Transportation Sales Manager for Kenall, a manufacturer of lighting products for tunnels and underpasses.