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34 A utility pole in a high-risk location is defined as one placed in a site within the roadway envi- ronment where there is an above-average risk of being struck by an errant motorist and where serious injury or death is a likely outcome of such a collision. It has been estimated that no more than 1/10 of 1% (0.001) of utility poles within highway rights-of-way are atypically exposed and thus considered to be at high risk of being struck, as discussed previously. Past research established that identifying and treating these poles not only can reduce the associated crash risk but also can be cost-effective in many situations, as indicated in the cost-effectiveness section of TRB State of the Art Report 9 (Ivey and Scott 2004) and the Gabler, Gabauer, and Riddell (2007) study on New Jersey DOTâs breakaway poles. The data confirm some common types of roadway environments that can be considered when identifying high- risk locations. Some of these exposure situations are described in Ivey and Scott (2004) and include poles that are located as follows: â¢ In the critical quadrants of an intersection (Figure 12) â¢ On the outside of curves (Figure 13), especially on curves where the advisory speed is lower than the design speed of adjacent tangent sections (which can be especially critical at the apex of vertical curves where the S-curve is hidden until the crest is reached) â¢ On the roadside immediately after, and in line with, a lane termination â¢ In an area exposed to oncoming traffic in the zone where the pavement narrows significantly â¢ In the median of divided roadways â¢ On traffic islands exposed to oncoming traffic â¢ In an area adjacent to reversed curves when the pole line moves from one side of the roadway to the other side. The aforementioned roadway environments and conditions are presented and discussed in TRB State of the Art Report 9 (Ivey and Scott 2004, pages 48â51). A single collision is not necessarily synonymous with a high-risk pole, but even a single event should constitute a reason to assess that poleâs location. Figure 13 and Figure 14 both show examples of high-risk poles, with the pole only a few inches outside of the travel lane and on the outside of a horizontal curve; Figure 14 also documents damaged poles. Several published methods may be useful in determining locations where crashes are probable: for example, by setting up a pole exposure record system or by systematically evaluating the relative exposure within the utility system. Once exposure to collisions is determined as a part of a comprehensive, prioritized, and cost-effective safety program, one or more of the five different analytical methods to identify high-risk poles can be used. These methods are all related to the numeric frequency, collision rate, quality control, crash severity, or some combination of those four characteristics. These approaches are described in TRB State of the Art Report 9 (Ivey and Scott 2004, page 54) and are emphasized in the latest work by Gabler, Gabauer, and Riddell (2007). C H A P T E R 5 Identification of Utility Poles in High-Risk Locations
Identification of Utility Poles in High-Risk Locations 35 Figure 12. High-risk intersection zone (Ivey and Scott 2017). Figure 13. Example of high-risk pole locations on the outside of a horizontal curve (Photo: Charles V. Zegeer).
36 Utility Pole Safety and Hazard Evaluation Approaches TRB State of the Art Report 9 (Ivey and Scott 2004, pages 18â21) describes a three-path approach to reducing utility pole fatalities, consisting of what are termed the Best Offense, Best Bet, and Best Defense strategies, defined as follows, to address utility pole safety problems: â¢ Best Offense. This approach identifies where an overrepresented number of collisions are occurring, assesses available countermeasures, prioritizes these high-risk poles for treatment, and implements the improvements. â¢ Best Bet. This approach involves prioritizing potentially hazardous poles and roadway sections (using statistical prediction algorithms) before a crash history develops and implementing appropriate improvements. â¢ Best Defense. This approach complements the first two and entails striving to meet the recommendations of the Roadside Design Guide (AASHTO 2011b) and Ivey and Scott (2004). The Best Offense requires the documentation of collisions to better pinpoint specific locations or segments of highways where an atypical number of collisions have occurred and are occurring. Such data would be available through police crash reports and UO maintenance records. The Best Bet is an effort to identify where collisions are most likely to occur in the future. It requires a DOT or UO with knowledge of the roadway system, including utility positions in a right-of-way, to detail where vehicle exposure to poles is most significant. Predictive algorithms are available for this calculation and include traffic density and speed, pole frequency, and pole lateral placement. The Best Defense also relies on knowledge of the highway and utility systems. Examples include large rigid wooden poles, which present a real danger to passing motorists because the poles are so close to the roadway (Figure 15). More telephone poles are located close to the roadway on a tangent section (Figure 16), which can also pose a high risk of serious injury (Ivey and Scott 2017). Figure 14. Examples of damaged high-risk poles (Photos: Kevin Zegeer).
Identification of Utility Poles in High-Risk Locations 37 Figure 15. Examples of high-risk poles too close to the roadway (Photos: Charles Zegeer). Figure 16. High-risk poles along a tangent section (Image: Delaware DOT).