Report suggests ways to improve lighting on roads.
In the report, the team developed recommendations for U.S. transportation agencies in areas such as visibility design technique, dynamic road lighting, pavement reflection factors, master lighting plans, and lighting techniques for roundabouts, crosswalks, or pedestrian areas. In addition, the team provided recommendations on signs and equipment quality level and maintenance. The following is excerpted from the report, which is available at www.international.fhwa.dot.gov.
Dynamic Road Lighting. In the Netherlands, highway engineers have installed a dynamic roadway lighting system that can be operated at three levels, depending on the amount of traffic and weather conditions. The high level is 2 cd/[m.sup.2], the normal level is 1 cd/[m.sup.2], and the low level is 0.2 cd/[m.sup.2]. The crash rate for the 0.2 cd/[m.sup.2] system, when operated at low traffic volumes, was acceptable. From these results it was determined that new systems will be installed to operate at 1 cd/[m.sup.2] and 0.2 cd/[m.sup.2]. A similar road is currently being installed in Finland.
The French are studying retroreflectivity and active luminous devices. Similarly, the acceptability of different types of guidance systems is being researched in the Netherlands.
As an approach to more dynamic management of roadway lighting, the panel recommends investigating the application of dimmable lighting systems, turning off lighting systems, and alternative guidance systems.
Pavement Reflection Factors. All of the countries use the luminance design method for roadways. Several countries noted that there are problems with the standard "R-tables." The initial luminance values measured in the field vary from the values predicted by the design calculations that used the standard R-tables.
It was stressed to the panel that, when doing field measurements, the roadway must be dry and the temperature must be above the dew point. It was also noted that better correlation between calculated and measured values is obtained when measurements are made in the summer.
The French are researching the photometric properties of road surfaces. The evolution of road surface technology and the use of bright and colored road surfaces necessitated the research. Examples of new road surfaces are "quiet" and "water-draining" pavements and thin asphaltic concretes and surface dressings. The French also are examining the possibility of using a virtual reflectometer for field measurements.
Pavement reflectance is an important element of lighting design. The panel recommends that more research, including field measurements, be conducted in order to overcome the acknowledged inadequacy of the R-tables for pavements.
Master Lighting Plan. A number of European cities have master lighting plans. The plans are based on providing safety, beautification, and security for goods and people. Urban lighting is viewed as a key component of city management.
The panel encourages the development of master lighting-design plans to improve the coordination of roadway and urban lighting in such matters as lighting levels and styles and themes for safety, security, and beautification.
Crosswalk and Pedestrian-Area Lighting. The Swiss have modified lighting techniques to provide vertical illuminance, which allows pedestrians in crosswalks to be seen in positive contrast. The result has been a lowering of fatalities by two-thirds. Other countries also cited the importance of vertical illumination in pedestrian areas to enhance easy identification.
The panel recommends the consideration of vertical illuminance as a design approach to improve safety in crosswalks and other pedestrian areas.
Crashes and Lighting. The police in Zurich, Switzerland, presented an extensive accident report. The panel found it interesting that the police analyze the cause of automobile accidents in the Zurich area and make recommendations for lighting applications.
The panel recommends the development of reporting systems that consider the lighting conditions at crash scenes.
Equipment Quality Level and Maintenance. The European lighting equipment generally appeared to be of a high quality, and very few roadway lighting outages were observed. The lighting systems were generally relamped on a group basis, typically on a 3- to 5-year cycle. Maintenance of tunnel lighting systems is generally conducted on a shorter cycle that coincides with the cycle for washing.
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|Title Annotation:||Traffic Control & Lighting|
|Date:||May 15, 2003|
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