| Contextual Infrastructure Planning and Design |
| It's Time to Look Beyond the Roadway: New Lighting
Standards |
| By Paul Lutkevich, Boston, Massachusetts 1-617-426-7330 lutkevich@pbworld.com
|
| Roadway lighting designers
have always been concerned about providing adequate visibility for
drivers but often did not look beyond the roadway. Now a new national
standard will help to focus attention on pedestrians and areas adjacent
to the roadway. |
|
Figure 1: Public right-of-way between property lines |
Figure 2: High vertical illuminance for pedestrians |
The Roadway Lighting Committee of the Illuminating Engineering Society
of North America (IESNA) has issued a new national standard for roadway
lighting in the U.S. This, the first revision to the document in 17
years, addresses issues long ignored in roadway lighting. The most
important of these are the pedestrian and the overall aesthetics and
integration of the roadway lighting system with its surrounding area.
Integration
The focus of previous versions of the American National Safety Institute
(ANSI)/IESNA RP-8 "Recommended Practice for Roadway Lighting"
was on the roadway surface and a driver's ability to see obstructions
and hazards in the roadway. The newly defined area of concern is the
entire right of way (ROW), including pedestrian zones. Elements within
the ROW can include landscaping, signs, bus shelters, street furniture,
outdoor café seating, banners, and many other elements that
must be coordinated architecturally to achieve an integrated and harmonious
outdoor environment (Figure 1).
Pedestrian
Lighting
Scale. In areas with a large number of pedestrians,
the pole size and luminaire mounting height should be designed to
a more human scale. This means the use of 3-m to 6-m (10 foot to 20-foot)
poles instead of typical 10-m to 15-m (35-foot to 50-foot) standards.
In many cases, the designer may find that a pattern of higher roadway
poles with cut-off luminaries lighting the road can be reasonably
supplemented by pedestrian scale luminaries for sidewalks and plaza
areas.
Security. Vertical illuminance (Figure 2) is
provided so pedestrians feel a sense of security. The ability to see
an approaching person's face, and thus gauge his or her intent, has
a significant impact to how safe one feels in a given situation. (Figure
3 on the following page) Unfortunately, most roadway lighting systems
do a poor job of meeting this goal, which is why it is so important
to have a small percentage of vertical light in high pedestrian environments.
The new RP-8 offers criteria for vertical illuminance covering different
areas. These new criteria should assist the designer in providing
a system that will be both comfortable and support a sense of safety
and security.
Figure 3: Vertical illuminance for facial recognition (left) |
Figure 4: An example of fill lighting |
Overall Aesthetics
Vertical Surface Illumination. In some environments, like downtown
and urban areas, the use of vertical illumination is necessary for
several reasons. In addition to pedestrian concerns mentioned above,
it provides illumination of building facades to produce fill lighting
that defines and highlights the night scene (Figure 4).
Glare.
With enhanced requirements for vertical illuminance, there is an increased
possibility of glare having a negative impact on the visual environment
and hindering people's ability to see and enjoy the surroundings.
As a result, a balancing glare criterion has also been included in
the new recommendation that, if applied, will help to limit the amount
of discomfort and disability that glare can cause in an outdoor environment.
This glare criterion, called a veiling luminance ratio, contrasts
the brightest source in an observer's field of view with the overall
scene (road) brightness.
Summary
With the introduction of this nationally recommended practice for
lighting roadways and adjacent areas, designers in the U.S. now have
a tool to improve the outdoor visual environment while still satisfying
all of the functional requirements necessary to develop a safe roadway
system. |
|
| Paul Lutkevich is Chair of the Illuminating
Engineering Society of North America Roadway Lighting Committee. He
has 18 years of experience in lighting design for infrastructure and
outdoor lighting projects. Paul received an International Illumination
Design Award for his use of light guides and has written and spoken
extensively on urban lighting and outdoor lighting issues. |
|
