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14 Statement of the Problem The unforgiving nature of utility poles has been recognized since the 1960s. This knowledge is as old as highway engineersâ recognition of the need for forgiving roadsides, a concept that found widespread understanding and acceptance some time before AASHTO published the revolu- tionary Design and Operational Practices Related to Highway Safety, known as the Yellow Book (AASHTO 1967). In their study, Graf, Boos, and Wentworth (1976) estimated that collisions with utility poles accounted for more than 5% of nationwide crashes, more than 5% of total nation- wide traffic fatalities, and more than 15% of the deaths associated with fixed-object collisions. During the intervening years, the design of roadsides has changed dramatically. Breakaway ground-mounted sign and luminaire supports, crash cushions, traversable clear zones, crash- worthy guardrails and bridge rails, and safer drainage structures are just some of the changes that likely have saved tens of thousands of lives. Some STAs have improved their utility pole- placement policies, and designers and crews routinely strive to place new utility poles as close as practical to the right-of-way line, per federal guidelines. Many utility poles in high-risk locations before 1967 have been removed, relocated, or improved somehow to enhance safety. According to Ivey and Scott (2017), estimates suggested that as few as 100,000 poles (out of the 100 million poles in the nationâs highway rights-of-way) are in high-risk areasâonly 1/10 of 1% (0.001) of existing poles, a mere fraction of the total number of roadside utility poles throughout the country. Nonetheless, this low percentage of poles was cited as still posing serious roadside hazards to passing motorists on the nationâs highways. Figure 4 shows an example of a utility pole located in a high-risk area (in this case, a rigid pole that is close to the road at a drive- way where vehicles turn both right and left into and out of the driveway). Ivey and Scott (2017) made the point that addressing only a small fraction of all existing utility poles along roadways would have a disproportionately positive effect on roadside safety. Highway engineers have consistently advocated the maintenance of a clear zone or a clear recovery area along roadsides; statistically, that solution should minimize or eliminate the danger for 80% of the vehicles leaving the roadway (AASHTO 1967). Furthermore, transporta- tion engineers have consistently tried to eliminate rigid objects within the clear recovery area, and many promote the practice of removing rigid poles. AASHTO Design Guidelines National AASHTO guidelines have helped guide STAs in recent years on roadway and roadside design, including the placement and treatment of utility poles. Such publications include A Policy on Geometric Design of Highways and Streets (6th Edition) (AASHTO 2011a), sometimes called C H A P T E R 2 Historical Perspective
Historical Perspective 15 the Green Book, and the Roadside Design Guide (AASHTO 2011b). The Green Book specifies that utility lines should be placed as close as practical to the highway right-of-way line. Such installations should also preserve space for potential future road improvements and utility operations and should be designed to enable utility line servicing that causes minimal traffic interference. Utility lines should also fit within the clear roadside policies that are appro- priate for a given highway type or functional class. Utilities on rural or urban freeways should conform to AASHTOâs A Policy on the Accommodation of Utilities within Freeway Right-of-Way (AASHTO 2005b). For highways and streets with noncontrolled access, applicable guidelines come from AASHTOâs A Guide for Accommodating Utilities within Highway Right-of-Way (AASHTO 2005a). For rural roadways, the Green Book (AASHTO 2011a) specifies that poles should not normally be situated in the median of divided highways. Furthermore, rigid objects such as utility poles (and other constructions that may be struck by vehicles that run off the road) should not be located in a highway clear zone. The Green Book refers to the Roadside Design Guide (AASHTO 2011b) when discussing the width of clear zones for freeways, rural arterial streets, and high-speed collector streets. For low-speed rural collector roadways and rural collector roadwaysâexcept for roads with average daily traffic (ADT) of 400 or fewer vehiclesâthe minimum desirable clear zone width is 7 to 10 feet. Several statements in the Green Book consider the placement of utility poles on urban streets. For example, on curbed urban streets, utilities should be situated in the border area between the sidewalk and the curb, at least 1.5 feet from the face of curb. Furthermore, wherever practical, the utilities should be located behind the sidewalk, further from the road. For roads with shoulders instead of curbs, a clear zone should be implemented, without rigid poles. The Roadside Design Guide (AASHTO 2011b) stated that the most desirable solutions for utility poles involve placing them where they are least likely to be struck or instead burying the utility lines. The use of breakaway designs was also suggested as a successfully crash-tested alternative. STAs and UOs should make every effort to install utility poles as far from the road as feasible during new construction and major reconstruction. The recommendation for agencies was to identify sites that exhibit a high concentration of utility pole crashes and then to implement appropriate improvements. Figure 4. Utility poles located close to roadway (Photo: Kevin Zegeer).
16 Utility Pole Safety and Hazard Evaluation Approaches Wherever practical, utility poles should not be installed in ditches, near the turning radii of intersecting roads, or on the outside of horizontal curves. If a series of utility poles are the closest objects to the roadway, delineation of each pole is highly recommended. The Roadside Design Guide (AASHTO 2011b) describes urban roadside locations. The most critical urban roads in need of possible improvement are characterized as those with a history of roadside crashes, often with other specific hazardous roadway and roadside features. Severe roadside crashes are most likely when vehicles are operating at higher speeds. The guide observes that the 1.5-foot minimum distance from the road is not intended to represent a clear recovery area, noting that vehicles can easily jump a curb and strike a pole installed at that distance. The recommendation is that the road designer apply wider lateral offset distances, whenever practical, between the roadway and rigid objects such as utility poles. During highway reconstruction, the crash history of the site should be considered when determining the appropriate roadside treat- ment for each roadway segment. The recommended safety hierarchy for designing roadsides at each location specifies the following order of preference (AASHTO 2011b): 1. Remove the fixed object 2. Redesign the fixed object so that it can be safely traversed 3. Relocate the fixed object to a site where it is less likely to be struck 4. Reduce impact severity by using an appropriate breakaway device or impact attenuator 5. Redirect a vehicle by shielding the obstacle with a longitudinal traffic barrier 6. Delineate the fixed object if the previous options are not appropriate. Many of the specific types of treatments for accomplishing each of these design goals from the Roadside Design Guide (AASHTO 2011b) are discussed subsequently in this synthesis report. Challenge of Utility Pole Crashes The estimate is that utility poles represent more than 100 million rigid objects within highway rights-of-way (Horne 2001). Moreover, an estimated 75,000 vehicle collisions with such utility poles are reported every year (Foedinger et al. 2003). That number corresponds to more than 4 million utility pole collisions over the past 50 yearsâand currently about 200 collisions per day, or 9 collisions per hour, or one collision every 7 minutes (Scott and Ivey 2015). One factor that perhaps might be influencing the response by some agencies to address the utility pole crash problem is the downturn in annual utility pole fatalities from almost 2,000 in 1975 to roughly 900 to 1,000 in recent years. Researchers generally acknowledge that the reduction in fatalities (per 100 million vehicle miles) is primarily the result of a transition from at-grade highways to the access-controlled freeways and interstate highways that dominate the bulk of highway mileage today. Other factors (such as a higher percentage of seat belt use, safer cars, stricter penalties for drunk driving) are also contributing to this downturn in utility pole fatalities in recent years. Figure 5 depicts the cumulative number of fatalities from 1965 through 2015, with an esti- mate of at least 63,000 fatalities due to utility pole collisions over those 50 years. The more than 900 people killed annually because of collisions with utility poles is more than double the 408 deaths in 221 fatal crashes in the United States in 2016 resulting from all airline crashes combined (NTSB 2018). Some researchers have stated that most STAs and UOs do not give adequate attention to the utility pole safety problem. If the more recent ratio of 30,000 injuries per 1,000 fatalities holds, this would equate to more than roughly 2 million injuries between 1965 and 2015.
Historical Perspective 17 Figure 5. Total fatalities due to utility pole collisions since 1965 (Ivey and Scott 2017). The rate of utility pole fatalities has not seen dramatic reductions in the past decade. If the rate of fatalities is allowed to continue at close to 1,000 per year for the next 10 years, the total number of fatalities due to collisions with utility poles since the advent of the auto- mobile will approach an estimated 100,000. The next section reviews previous research regarding factors that influence utility pole crash frequency and severity, summarizes the crash treatments and the development of expected crash effects (the CMFs), and addresses articles and reports that suggest methods for implementing a comprehensive program to address the utility pole safety problem (Ivey and Scott 2017).