Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
32 To provide readers with specific examples documenting transportation agency experience with isolated rural intersection lighting and its alternatives, this chapter describes several examples provided by state DOTs. These agencies are gratefully acknowledged for their contributions to this synthesis report. Vermont: Isolated Rural Intersection Lighting A T-junction intersection between state highway VT-116 and Cheesefactory Road in South Burlington, VT, had a nighttime crash frequency that was 40% higher than daytime crashes. The intersection experienced a high number of single-vehicle crashes, all occurring at night. To address these problems, the Vermont Agency of Transportation initially installed a double large arrow to help prevent vehicles from running through the intersection when conditions were dark. In addition, a Stop Ahead sign on Cheesefactory Road was installed to provide an extra cue in dark conditions that the road is about to end. A reflective-post panel was also applied to the stop sign post to increase nighttime conspicuity. Finally, a roadway luminaire (FigureÂ 28) was installed at the intersection; this required bringing electrical power to the intersection and installing a new pole. The municipality is responsible for paying for energy and maintenance. The LED luminaire installed at this intersection uses 37 W of power. Because the installation occurred recently (Fall 2019) it is difficult to estimate quantitative safety impacts of the lighting system, but there have not been any crashes reported at this location since the initial installation. The original estimated cost for the project was $19,000, but because it was necessary to dig under- ground in the vicinity of the existing transmission line to bring electrical power to the luminaire, the final project cost was $39,000. The state used HSIP funds to pay for the installation. Initially, this project was undertaken as a low-cost intervention with an expected benefit/cost ratio of 13.47, but if the full cost had been known beforehand, the project would have been deferred to include it as part of a larger project that will include the construction of turn lanes at this intersection. Utah: Solar-Powered Rural Intersection Lighting The Utah Department of Transportation has installed multiple solar-powered rural lighting systems, including a rural intersection (Figures 29 and 30) in the Spring of 2016, and at a rail crossing in the Fall of 2016 (FiguresÂ 31 and 32). Two 54Â W LED luminaires with a CCT of 4,000Â K were installed at the intersection, and one luminaire was installed at the rail crossing, all on 25-foot poles with 8-foot mast arms. The power for each luminaire is provided by a 62-inch by 32-inch photovoltaic panel specified to provide 190Â W of power; the panels are mounted on the luminaire poles. C H A P T E R 8 Case Examples
Case Examples 33Â Â Figure 28. Photograph of streetlight mounted at a T-junction intersection in Vermont. Courtesy of Vermont Agency of Transportation. Figure 29. Daytime photograph of solar-powered luminaires at an isolated rural intersection. Courtesy of Utah Department of Transportation. As estimated in Spring 2016, the cost for each luminaire, including the pole, mast arm, controller cabinet, batteries, and photovoltaic panel, was $8,200. The expected life of the photovoltaic panel is 25 to 30Â years, but the storage batteries will need replacement after 10Â years. Utah DOTâs experience with solar-powered lighting so far has been positive. Officials from the local counties and municipalities were pleased with the lights, and Utah DOT maintenance staff has not had any problems with the lights since they were installed. Anecdotally, the agency believes that drivers frequently missed making turns at unlighted intersections and that the new lights help prevent this. Because the installations are still relatively new, the DOT does not yet have crash data for these systems. Utah DOT has installed similar solar installations at
34 Lighting Practices for Isolated Rural Intersections Figure 30. Nighttime photograph of the solar-powered intersection lighting system in FigureÂ 29. Courtesy of Utah Department of Transportation. Figure 31. Daytime photograph of solar-powered lighting at a rail crossing. Courtesy of Utah Department of Transportation.
Case Examples 35Â Â Figure 32. Nighttime photograph of the solar-powered lighting from FigureÂ 31. Courtesy of Utah Department of Transportation. three other intersections. Recent changes in the way budgeting for lighting within the agency is performed means there is no longer a dedicated budget for lighting projects such as these, but Utah DOT will still consider solar-powered lighting at rural intersections in the future. Maine: Oversized Reflective Delineators As an alternative to lighting at isolated rural intersections, the Maine Department of Trans- portation fabricated a set of oversized reflective delineators (FigureÂ 33) to install along the roadway near a rural intersection that was also adjacent to a curve. Originally, these types of reflectors were developed to help drivers identify moose crossings when animals would run in front of them and temporarily obscure the line of sight to the reflector. While moose crashes initially were reduced, they eventually increased, but Maine DOT received many comments from the driving public that the reflectors helped them to navigate the road and to identify curves and intersections in rural areas when there was no roadway lighting present. The delineator is 12Â inches by 16Â inches and folded along the center of the longer dimen- sion at a right angle. The delineators were mounted to short posts at headlight height along the roadway edge, placed at a 45-degree angle to the road so it could be seen by traffic in both directions (FigureÂ 34; see also FigureÂ 5). Currently, there are no data that permit an estimate of the safety benefit for this single intersection where the reflectors were used, but the DOT is considering plans to install them at many locations.
36 Lighting Practices for Isolated Rural Intersections Figure 33. Close-up view of the oversized reflective delineator. Courtesy of Maine Department of Transportation. Figure 34. View of oversized reflective delineators along the road near a rural intersection. Courtesy of Maine Department of Transportation.