There are fewer crews out working on the road in the winter, partly because of the conditions but also because the days are shorter and there’s not a lot of light by which to work. In fact, the days can get short enough, especially as you go farther north, that even a normal day involves some “night work.” Construction work zones are also increasingly active at night during the summer to accommodate traffic and tight project schedules. At any time of the year, road construction at night requires proper lighting to ensure quality work and for everyone’s safety. In this edition of the RoadReady newsletter, we’ll examine some of the options available for lighting the work zone and providing visibility during nighttime construction activity.
To design a lighting plan for a construction work zone, the critical objective is to provide a certain level of illumination, or light falling on a surface. The amount of illumination can be measured in footcandles (the light of one candle uniformly distributed over one square foot of surface area) or lux (a metric equivalent to the footcandle) and divided into three levels: Level I is required throughout the work zone, while active work areas where equipment is operating require Level II or Level III, depending on the difficulty of the work and how much it depends on worker visual performance. Keep in mind that illumination is not simply a matter of what type of lighting option is being used. Illumination depends on the intensity of the lights, the number of light sources, and the distance at which those light sources are placed from the work area to be lit.
If there are existing streetlight fixtures at the project site, they can be incorporated into a lighting plan for nighttime construction work, but don’t assume that they will provide sufficient light. For example, a flagger position might be selected to take advantage of an area that is already lit, but additional temporary lighting will likely also be needed for safety. Although it does contribute, fixed lighting was designed for traffic under ordinary conditions, not for the additional requirements of a construction work zone.
Portable lighting systems such as a trailer-mounted light tower can easily be moved around to different project locations and quickly raised into position to illuminate the work zone area. This type of lighting should be able to generate the minimum level of light required for nighttime construction work zones. Supplemental lighting such as floodlights may be necessary for specific tasks.
Portable light towers can create glare that might temporarily blind workers or motorists who are suddenly exposed to the light. To minimize this problem, tower lights should be aimed downward at the work they are illuminating, not outward or at an angle. The positioning of construction activity and spacing of lights must be properly considered. Workers and equipment should be as close to the center of the lit area as possible to avoid being backlit or lost in shadows.
Balloon lights are a common term for a type of temporary lighting often used in road construction work zones. This refers to a system where the light source is surrounded by a translucent material that diffuses the light, scattering it through the work area instead of producing a focused beam. The name alludes to the fact that these lights typically have roughly the shape of a balloon. One major benefit of balloon lights is that they produce significantly less glare than ordinary light towers or equipment headlights.
Some construction equipment may have lighting fixtures added to it for night work, especially for larger machinery like a paver. Many of the portable fixtures used for area lighting can also be mounted on construction equipment in this way. Especially for lights that are not factory-installed, they should be checked to make sure the light shines in the intended direction and will not cause excessive glare.
Mounted lighting can be especially useful when the work zone covers a relatively large area and it is not practical to supply lighting equipment for the entire area throughout. When construction operations are continuous and lighting can accompany the equipment, this can reduce the effort required to repeatedly set up and move portable area lighting.
Some lighting equipment serves primarily to warn oncoming vehicles and is less focused on providing illumination for the work area. Flashing or rotating beacons are recommended on all work vehicles and equipment for nighttime use. Ideally these lights will be mounted in pairs on either side of the vehicle, which helps oncoming drivers judge their distance.
Warning lights should generally be displayed anytime the equipment is operating on the closed roadway. This helps alert both surrounding traffic and workers in the construction zone. The lights also indicate that the vehicle is authorized to operate in the work zone.
Lighting and Visibility
One more thought related to lighting and work zone safety at night is that lights can only ever provide part of the solution—the other part is making sure you are visible. Proper high-visibility safety apparel must be worn. The classes of garments approved for nighttime work include retroreflective material, which picks up light that shines on it and reflects it back to the source, making you more visible to drivers and equipment operators. Since no amount of temporary lighting will be as good as broad daylight, high visibility apparel helps make up the difference.
In order to do quality work, having the proper light to see what you’re doing is essential. Being able to see and be seen in the work zone is critical for safety as well. For any road construction project that involves night work, ensuring adequate lighting is always going to be a critical issue to tackle.
National Cooperative Highway Research Program, Report 476, Guidelines for Design and Operation of Nighttime Traffic Control for Highway Maintenance and Construction: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_476.pdf
National Cooperative Highway Research Program, Report 498, Illumination Guidelines for Nighttime Highway Work: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_498.pdf
Illinois Department of Transportation, Safer Nighttime Construction Zones Through Better Lighting: http://onlinepubs.trb.org/onlinepubs/trnews/trnews260RPO.pdf