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4 C H A P T E R 2 State Policies and Practices for Isolated Rural Intersection Lighting Approximately 70% of states reported that they have guidelines or policies to help decide where and how to implement lighting at isolated rural intersections (FigureÂ 1). For the most part, these policies address conventional intersection forms involving junctions of two road- ways. Many agencies, 73% of survey respondents, also have guidelines for lighting roundabouts in rural, remote areas (FigureÂ 2). A review of policies identified state agencies that require lighting to be installed at all roundabouts (Florida DOT 2013; Maryland SHA 2017; South Carolina DOT 2017) as well as a local agency (Jefferson County [MO] DPW 2018). Only one case was identified where a state DOT chose to make the installation of lighting optional at rural roundabouts (i.e., Virginia DOT 2019). Other facilities that might be considered rural intersections include at-grade railroad crossings. The literature review identified a state agency (Caltrans 1996) and a local agency (Kitsap County [WA] 2007) with specific guidance on lighting for rural at-grade rail crossings. Among survey respondents, just over 25% reported having guidance for these facilities (FigureÂ 3). Two state DOTs indicated that they decide to install lighting at these facilities on a case-by-case basis. The broad class of roadway facilities known as intersections can include various types including interchanges, diverging diamonds, continuous flow intersections, single-point urban interchanges, and intersections with walkways and bikeways. More than one-half (57%) of the agencies responding to the questionnaire reported that they had specific policies for illu- minating these types of intersections when such intersections were in isolated rural locations (FigureÂ 4). Warranting Issues Chapter Summary â¢ Many states have general policies for when and where to install lighting that are applied to isolated rural intersections. â¢ Common warranting criteria include traffic volume, nighttime crash rate or history, geometry, and weather, as well as specific intersection types, especially roundabouts. â¢ Relatively few procedures are in place to guide transportation departments when they receive requests for rural intersection lighting from local municipalities or the public.
Warranting Issues 5Â Â Figure 1. Responses to âDoes your agency have any policies or guidance for determining where and how to implement isolated rural intersection lighting?â Figure 2. Responses to âDoes your agency have policies or guidance for determining where and how to implement lighting that is not part of a continuous roadway lighting system for rural roundabouts?â Figure 3. Responses to âDoes your agency have policies or guidance for determining where and how to implement lighting that is not part of a continuous roadway lighting system for rural at-grade railroad crossings?â
6 Lighting Practices for Isolated Rural Intersections Alternatives to Lighting at Isolated Rural Intersections Lighting is only one safety element that can be used at isolated rural intersections and, in some cases, may not be the preferred treatment. TableÂ 1 summarizes findings about some of these alternatives from the published literature. In general, the literature cited in TableÂ 1 suggests that flashing beacons (signal lights) did not appear to be very effective and that illumination systems would be likely to have a more substan- tial safety benefit. While intersection conflict warning systems may be more effective overall than lighting, contradictory conclusions from some of the studies of these systems and their higher initial costs may make these more challenging to specify in many isolated rural locations. Alter- natives using reflective signs, marking, and other elements may be cost-effective because these approaches do not require the provision of electricity at a rural location to be effective, even if their relative safety impact may be small. A substantial percentage of agencies responding to the questionnaire (>50%) also reported experience with many of these alternatives (FigureÂ 6). Among the options provided by those who selected âOtherâ as a response to this question were high-friction surface treatments, illu- minated bollards, flashing stop signs, and reflective treatments for posts. Factors Considered in Warranting Numerous factors have been considered by transportation agencies, or recommended for consideration by researchers, in deciding whether or not to install lighting at isolated rural inter- sections. TableÂ 2 summarizes these factors with examples of warranting thresholds or criteria that would support the installation of lighting in these facilities. The references cited in TableÂ 2 primarily address conventional intersection types, not roundabouts, interchanges, or railroad crossings. The responses of the survey participants (FigureÂ 7) indicate that they use many of the same factors as those in TableÂ 2 regarding the warranting of lighting at isolated rural intersections. These factors are also largely supported by findings from the research literature. Preston and Schoenecker (1999) suggest that warranting criteria for rural intersection lighting, such as traffic volume, might be reduced to allow lighting to be considered at more intersections and thereby have a larger overall benefit on reducing nighttime crashes. Leipholtz (2017) described a specific Figure 4. Responses to âDoes your agency have policies or guidance for determining where and how to implement lighting that is not part of a continuous roadway lighting system for other rural locations?â
Warranting Issues 7Â Â Supplementary pavement markings â¢ Could be considered before (Government of Alberta 2011) or in conjunction with (Green et al. 2003) lighting â¢ Can be effective (Torbic et al. 2015; Findlay 2017; TRIP 2019) Flashing lights/beacons (defined as some type of light source visible to approaching drivers, and usually operated with a flashing pattern) â¢ Could be considered before lighting (Government of Alberta 2011) â¢ Some studies have found them to be relatively ineffective (Preston and Schoenecker 1999; Rummel, Klepper & Kahl or Rummel et al. 2019) and some agencies are removing them (North Dakota DOT 2020) Intersection conflict warning system â¢ Reduces crashes by 27% and may be more effective than lighting (Lund and Jackels 2019), especially where there are limited sight lines (Civil Science 2018) â¢ Can be relatively expensive (Fuller 2019) and prone to maintenance problems (Hayes and Leuer 2019) â¢ Some recent evidence suggests they may not be as effective as other studies found (HDR 2019; Hayes and Leuer 2019) Rumble strips â¢ Not effective in some studies (Preston and Schoenecker 1999) â¢ Found effective in some studies (Torbic et al. 2015) â¢ Could be used in conjunction with lighting (Sand 2018) Reflective posts â¢ Could be considered before lighting (Leedy 2019) Turn lanes â¢ Can improve safety (Van Schalkwyk and Milton 2010) Alternative Notes and References Oversized/improved signage and delineation (see Figure 5) â¢ Could be considered before (Government of Alberta 2011; Leedy 2019) or in conjunction with (Green et al. 2003) lighting â¢ Can be effective (TRIP 2019) Stop ahead sign â¢ Could be considered before lighting (Government of Alberta 2011) Table 1. Summary of Literature Review Findings about Alternatives to Lighting for Isolated Rural Intersections. set of criteria that could be used to prioritize which rural intersections might be outfitted with lighting, including: â¢ The angle between intersecting roads differs from the right angle by more than 15Â°. â¢ The intersection is within 1,000Â feet of a curve. â¢ The intersection is near commercial development. â¢ There is a railroad crossing within 500Â feet. â¢ The location is more than 5Â miles from the nearest stop sign on a minor road (also suggested by Civil Science 2018). â¢ A crash has occurred at the location within the past 5Â years. â¢ There is high minor road traffic volume relative to the major road (also described by Torbic etÂ al. 2015). Regarding traffic volume, there is research support for using this factor in setting warrants. Bullough and Rea (2011) analyzed the relationship between intersection lighting and night- time crash reductions and concluded that, for rural intersections, a traffic volume of at least 1,900 vehicles per day along the major road would result in a benefit/cost ratio greater than 1. Similar criteria for traffic along the major and/or minor road of a rural intersection have
8 Lighting Practices for Isolated Rural Intersections Figure 5. Photograph of oversized reflective delineators along a curve adjacent to a rural roadway intersection, used as an alternative to lighting. Courtesy of Maine Department of Transportation. Figure 6. Percentage of agencies reporting using different alternatives to isolated rural intersection lighting.
Warranting Issues 9Â Â Warranting Factor Notes and References Traffic volume â¢ High traffic volume (Wright County [MN] 2002; New Mexico DOT 2020) o Average daily traffic (ADT) more than 3,500 vehicles/day (Iowa DOT 2013) â¢ A high percentage of turning vehicles (Colorado DOT 2005; New Jersey DOT 2015) Geometry â¢ Complex configuration or alignment (Nebraska DOT 2006; New Jersey DOT 2015; Maryland SHA 2017; Illinois DOT 2020; New Mexico DOT 2020) â¢ Major route changes direction (Iowa DOT 2013) Nighttime crash frequency â¢ Frequent nighttime crashes (Nebraska DOT 2006; Florida DOT 2013; Wright County [MN] 2002; Maryland SHA 2017; New Mexico DOT 2020) o More than 2.4 crashes/million vehicles in 3 consecutive years (Illinois DOT 2020) o More than 2.4 crashes/year in 3 consecutive years (Tennessee DOT 2018) Pedestrian activity â¢ Significant rural pedestrian activity at night (Nebraska DOT 2006; Tennessee DOT 2018; Illinois DOT 2020) Weather â¢ Recurring fog or smog at night (Tennessee DOT 2018; Illinois DOT 2020) Signalization â¢ Unsignalized intersections do not warrant lighting unless other criteria are met (Maryland SHA 2017) Atmosphere/aesthetics â¢ Desire to maintain a rural atmosphere may warrant little or no lighting (Harford County [MD] 2019) Request from a local municipality â¢ If not warranted by other criteria (e.g., crash frequency, traffic volume), a locality must agree to pay for installation and operation of the lighting system (Wright County [MN] 2002) Table 2. Summary of Warranting Factors and Criteria from Literature Review. Figure 7. Percentage of survey respondents identifying different warranting factors for isolated rural intersection lighting.
10 Lighting Practices for Isolated Rural Intersections been offered (Preston and Schoenecker 1999; FHWA 2012; Jefferson County [MO] DPW 2018); in general, a high frequency of nighttime crashes increases the likelihood that lighting would be beneficial at an isolated rural intersection (Fitzpatrick etÂ al. 2011). Locations with complex geometries are also reported as good candidates for rural intersection lighting (Hallmark and Hawkins 2014). As mentioned previously, certain intersection configurations, especially roundabouts, are determined by some agencies to warrant lighting regardless of any other factors (Jefferson County [MO] DPW 2018; Delaware News Desk 2019; Russell 2019; Thompson 2020), although at least one agency suggests that not all rural roundabouts require lighting (Virginia DOT 2019). Finally, some agencies at the local or county level of government have received requests by individuals from the general public to install lighting at one or more isolated rural intersections (Wickett 2015; Jefferson County [MO] DPW 2018). Some specific policies have been identified in the literature review that address such requests, such as who would pay for the installation and/or energy cost of lighting if it is not otherwise warranted by other criteria (Nebraska DOT 2006; Tennessee DOT 2018; Leedy 2019).