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45 Studies of Individual Treatments, Past and Present Fox, Good, and Joubert (1979) found that poles placed at the curb in Australia are three times more likely to be struck compared to those located 10 feet from the travel lane. Zegeer and Parker (1983) also concluded that the chance of a vehicle striking a utility pole diminishes greatly if the pole is 10 feet or more from the road. Poles at intersections, at lane drops, and on the outside of horizontal curves are also at higher risk of collisions than poles on tangent sections. The strategy of relocating high-risk poles to lower risk sites can often be cost-effective. Good, Fox, and Joubert (1987) conducted a study in Australia for Accident Analysis and Preven- tion, performing an in-depth analysis of 879 utility pole crashes at 795 sites and an analysis of 627 crash-involved vehicles. This study included crash modeling, use of crash costs, and devel- opment of cost-effective treatments for utility pole crashes. The authors also assessed vehicle factors that may be contributing to utility pole crashes. They concluded that pole crashes are four times more likely when roads are wet and that side and oblique impacts are generally more severe (because of occupant space penetration). This study also demonstrated that 65% of pole crashes entailed frontal impacts. A majority (61%) of pole crashes involved male drivers, typically in their late teens to early 20s. Alcohol was cited as a contributing factor in 38% of the crashes in the study, compared to a rate of 15% for other documented pole crash cases. More severe crashes occurred on curves than on tangent sections. Vehicles with tire tread depths of less than 3 mm were overrepresented in the pole crashes, particularly on wet roads, and underinflated tires increased the likelihood of crashes. Lower vehicle mass (i.e., smaller cars) exhibited more severe injury levels. Side-impact crashes were more severe than head-on crashes because of the shorter distance to the occupant compartment and the relative strength of the side of the vehicle. The Good, Fox, and Joubert (1987) study then calculated âloss reductionâ (i.e., the reduction in crash-related costs), which revealed findings including the following: â¢ Pole removal was the most cost-effective method. â¢ Crash barriers and attenuators would not be a cost-effective loss-prevention measure in urban areas. â¢ Crashes involving breakaway or yielding luminaire poles resulted in significantly lower societal costs compared to those of rigid luminaires. (Similar information on the effectiveness of breakaway or yielding utility poles is not currently well established.) Ray, Troxel, and Carney (1991) investigated the characteristics of side-impact collisions with fixed objects in the United States, using two data sources from NHTSA: the National Accident Sampling System (NASS) and FARS. The study cited trees and utility poles as the most frequently struck fixed objectsâand as the types of roadside obstacles causing the most severe personal C H A P T E R 7 Current Countermeasure Practices
46 Utility Pole Safety and Hazard Evaluation Approaches injuries. In terms of the part of the vehicle impacted in fixed-object crashes, the front of the vehicle collided first in about 65% of crashes, compared to 24% of crashes involving a side-impact. Of all fixed-object types struck, utility poles accounted for 26.3% of the side-impact crashes recorded in FARS and 30.2% of those in NASS. The study also found an overrepresentation in fatal crashes associated with ânarrow objectsâ (e.g., trees and utility poles). Ray, Troxel, and Carney (1991) also determined that side impacts with âbroad objectsâ such as guardrails were related to 18% of the collisions, with 12% of the fatalities. The side-impact fatality rate for guardrails was five times less than the same rate for trees and utility poles. They also noted that the chance of a motorist being involved in a fatal side-impact crash was three times higher on curved sections of roads compared to tangents. In the conclusions, they observed that the sides of vehicles are not as rigid as the fronts and that a near-side occupant in a side-impact crash is no more than 6 to 8 inches from the fixed object. Ray, Troxel, and Carney (1991) concluded: Certainly the greatest improvements could be realized if trees and utility poles were removed from certain hazardous locations along the roadway. Such relocation and removal programs will require state, county, and city officials to come committed to reducing this type of accident in their jurisdictions. . . . Roadside designers must make every effort to keep trees and poles away from the roadway, hardware developers must develop safety appurtenances for this scenario, automotive manufacturers must design more crash-worthy vehicles for side impacts, and local governments must commit themselves to removing fixed objects from hazardous locations. . . . Marquis (2001) conducted a study for the Maine DOT with the objective of identifying common factors associated with utility pole crashes to better specify corrective measures and to update current policies and reduce the number of such crashes. This study was performed in response to Maineâs recognition that it had a problem (ranking ninth nationally based on utility pole fatal collisions per miles driven) and that its policy was to relocate poles only when a roadway section is reconstructed or rehabilitated. Marquis (2001) analyzed a database of utility pole crashes between 1994 and 1998 to pinpoint risk factors, and a questionnaire was sent to all 50 states regarding their policies. The study recommended potential safety measures to enhance Maine policies. Some of the following conclusions were reached about factors related to utility pole crashes: â¢ Most utility pole crashes (87% of fatalities and 74% of crashes) occurred on rural roads. â¢ Excessive speed and driver inattention were common crash factors. â¢ Utility pole crashes often occurred on roads with little or no shoulder. â¢ Steep-side slopes were also commonly cited in utility pole crashes. â¢ Utility poles in the median or traffic island were also struck. â¢ At 18% of the utility pole crash sites, poles were situated on both sides of the road. Marquis (2001) recommended several steps to improve utility pole safety in Maine and to modify the stateâs utility pole location policy. These recommendations included annual reviews of crash records and the consideration of high-crash sites for improvement. Marquis (2001) recommended the following offsets for pole placement: â¢ Greater than 8 feet on roads with 25â35 mph speed limits â¢ Greater than 14 feet on roads with 40â45 mph speed limits â¢ Greater than 24 feet on roads with speed limits exceeding 50 mph. Other recommendations by Marquis (2001) include the following: â¢ Utility poles should be located at least as far back as the rear slope of the ditch lines. â¢ Guy wires should be placed on the back side of utility poles (i.e., further from the road than the closest point on the poles).
Current Countermeasure Practices 47 â¢ Poles should be eliminated on traffic islands, in medians, and across from T-intersections. Alternative safety structures should be used on poles that cannot be moved. â¢ For roadways with poles on both sides of the road, the poles on one side should be removed, and all utilities should be carried on the pole line on the other side of the road. â¢ The presence of poles on the outside of horizontal curves should be reduced, and the offset distance from the road should be increased where slopes exceed 4:1. If poles cannot be placed an adequate distance from the road, the Marquis (2001) report recommends considering âalternative safety structuresâ (e.g., steel-reinforced breakaway poles, low-profile concrete barriers, guardrails, or soft concrete cushions). Jinsun and Mannering (2002) analyzed run-off-road crashes on a 96.6-km (about 60-mile) section in Washington State, using empirical and methodological analysis techniques to study run-off-road crash frequency and severity. The purpose was to provide an indication of the effects of various countermeasure options on reducing the frequency and severity of roadway encroach- ment crashes. The study accounted for roadway geometrics, roadside geometrics, roadway characteristics, and run-off-road crash frequency and severity. Among its findings: the number of run-off-road crashes can be reduced by avoiding cut slopes, decreasing the number of isolated trees along the roadsides, and increasing the distance between the outside shoulder edge and the light poles. Jinsun and Mannering (2002) also identified various roadway and roadside features that contributed to crash severity. NCHRP Report 500 is composed of a series of guides in different volumes, including Volume 8: A Guide for Reducing Collisions Involving Utility Poles (Lacy et al. 2004). The overall objective of this guide focused on recommending countermeasures to reduce the frequency and severity of utility pole crashes. Also, Volume 6: A Guide for Addressing Run-Off-Road Collisions (NCHRP 2003) describes additional measures that might be helpful. The following three overarching objectives were recommended in Volume 8 of NCHRP Report 500 (Lacey et al. 2004): 1. Treating individual utility poles that are in high-crash and high-risk locations 2. Preventing the placement of utility poles in high-risk locations 3. Treating several utility poles along a corridor in an effort to minimize the likelihood of pole crashes by errant vehicles. Volume 8 of NCHRP Report 500 (Lacy et al. 2004) also encourages highway agencies to adopt a comprehensive approach, including non-engineering practices such as police enforcement of speeding laws, driver information and education programs, improvements in highway safety management systems, and measures to increase seat belt use by vehicle occupants. The 10 specific strategies described in that NCHRP guide address the three objectives listed above. Strategies 1 through 6 below relate to Objective 1; Strategy 7 focuses on Objective 2; and Strategies 8 through 10 are pertinent to Objective 3. Strategy 1. Remove poles at high-crash locations. This measure involves reviewing crash data to pinpoint those poles that have been struck one or more times in recent years. This strategy will require a field visit to identify these poles, ask questions about whether the poles are necessary at that specific location, and consider whether the poles can be moved to a lower risk location. Strategy 2. Relocate poles further from the road at high-crash locations to lower the risk of those sites. This strategy relates more to multiple poles in a line along a roadway section where collisions have occurred with some of the poles, where the poles are in high-risk locations (such as close to the road on a curvy roadway), or both. Because motorists are more likely to run off the road on curves rather than tangent sections, it follows that poles placed adjacent to the road on the outside of curves are at greater risk of being struck. Such higher risk locations could also
48 Utility Pole Safety and Hazard Evaluation Approaches be lurking at intersections or lane drops. Poles in traffic islands or at the top of a T-intersection (Figure 17) may also be at higher risk of vehicle collisions. Strategy 3. Use breakaway pole features. The strategy of using a steel-reinforced safety pole or a fiberglass pole is not directed at treating large numbers of poles but instead is an option for treating a few poles that are currently at a vulnerable location and, for practical reasons, cannot be removed or relocated. For example, this strategy may involve one or two poles close to the road on a horizontal curve where no additional right-of-way is available and where moving the pole is not feasible. In such cases, converting the pole to a yielding pole may be both practical and cost-effective in many situations. Strategy 4. Provide roadway devices to shield motorists at high-risk locations. This strategy places a guardrail or other longitudinal barrier in front of the poles. This option would create less of a hazard than the utility pole, even though a guardrail itself represents a fixed object that may produce occupant injuries in a collision. Employing such barriers may be particularly appropriate if the poles cannot be moved. In addition, barriers may be appropriate in locations that also are characterized by trees and other fixed objects or by steep roadside slopes on the roadside, so relocating the utility poles would not resolve the roadside hazard problem. The criteria for justifying guardrail installation include the following: â¢ The utility pole is located in the clear zone. â¢ Relocating or removing the utility pole is not possible because of right-of-way limitations or economic factors such as those associated with large transmission poles (Figure 18). â¢ Breakaway poles are not an appropriate solution because trees, steep slopes, or other roadside features would reduce the benefit accrued from such a feature. â¢ A guardrail or barrier would not create a greater hazard than the utility pole. â¢ A guardrail or barrier will not direct the striking vehicle into a higher risk hazard, such as a large tree or a steep slope. â¢ The guardrail face will be no closer than 2 feet from the edge of the road. The guardrail or barrier would be positioned with enough space between it and the utility pole so that a striking vehicle will not push the guardrail into the pole. Figure 17. Example where pole relocation can greatly reduce the risk of utility pole crashes, at the top of a T-Intersection (Photo: Charles Zegeer).
Current Countermeasure Practices 49 Strategy 5. Improve the driverâs ability to see the utility poles at high-risk locations. This strategy involves placing a reflective band or reflective markers (delineation) on the poles so that they are more visible at night in the shine of oncoming vehicle headlights. This measure does not reduce crash severity but, in some cases, may help the driver see the poles and take necessary action to avoid them. This projected outcome assumes that the errant vehicle is under some level of control or can be brought back under control after the driver sees the reflective devices. If the vehicle is already out of control, however, such delineation is not likely to reduce the likelihood of a collision. Strategy 6. Install traffic-calming measures to reduce vehicle speeds. This strategy relates to installing roadway geometric treatments to reduce the speed of motor vehicles on roads (in urban and suburban areas) in situations where direct treatments to the utility poles (e.g., pole relocation, shift to underground utility lines) are not feasible. Such measures can include road diets (reducing the number of lanes from a four-lane undivided highway to a three-lane road), installing speed monitoring cameras, narrowing the lane width (by using edge-line markings), installing speed humps, or implementing other countermeasures. Although not considered as traffic-calming measures, other options (e.g., paving the shoulder, installing edge-line rumble strips) are available for treating the roadway to reduce the likelihood of run-off-road crashes. Figure 19 shows an example of traffic-calming measures to reduce vehicle speeds that is based on narrowing the road, which can also provide for safer (and additional) pedestrian crossings. Strategy 7. Implement policies and guidelines to discourage positioning utility poles in the recovery area or at high-risk locations. This strategy adopts utility pole-placement guidelines that are sensitive to siting poles where they are at lower risk of being struck by motor vehicles. Such pole-placement guidelines, which are sensitive to highway safety concerns, can be useful not only when new utilities are installed but also when poles are removed and then reinstalled during construction and reconstruction projects. Examples of such pole-placement guidelines and policies that are geared to improving roadside safety are described in this report in Chapter 9 on case examples from STAs. Strategy 8. Install utility lines underground. This measure focuses on removing the utility poles and burying the lines underground. This strategy is normally quite expensive and therefore Figure 18. Example of utility poles (such as transmission poles) that cannot be relocated, requiring consideration of alternative treatments (Photo: Don Ivey).
50 Utility Pole Safety and Hazard Evaluation Approaches is cost-effective primarily along roadways where (1) the poles are very close to the roadway (e.g., 2 feet from the travel lane); (2) a very limited right-of-way means that the poles cannot reason- ably be relocated further from the road (because additional right-of-way cannot be purchased); and (3) no other obstacles (such as trees) lie in the clear zone and would still pose crash risks after the utility poles are removed. Installing utility lines underground is actually a fairly common measure used by some jurisdictions, partly for the aesthetic benefits of removing lines of utility poles. A candidate section for underground utilities is shown in Figure 20. Figure 19. Example of a traffic-calming measure, with a narrowing road and pedestrian crossings (Photo: Kristen Brookshire). Figure 20. Example of a good candidate for safety improvement by burying utility lines (Photo: Charles Zegeer).
Current Countermeasure Practices 51 Strategy 9. Relocate poles along a corridor further from the road, to less vulnerable loca- tions, or both. This strategy involves addressing needed improvements for multiple utility poles along a roadwayânot, for example, just a few poles that have been involved in collisions. The goal of this strategy is to relocate a row of poles that is currently placed in the clear zone of a roadway, with all poles located closer to the roadway than is advisable. Strategy 10. Reduce the number of utility poles along a roadway section. Fewer poles represent one obvious method for decreasing the number of pole crashes within a roadway section. In practical terms, this pole reduction can be accomplished in several different ways. (1) Multiple-use poles (shared utilities) require removing the row of poles on one side of the road and then, for sections that currently have poles on both sides of the road, doubling up multiple types of utility lines (e.g., telephone, electric, cable) on a single row of poles while eliminating the row of poles closer to the road. (2) Installing poles with greater spacing between them may certainly have the negative effect of requiring larger and more rigid poles at the longer intervals, therefore possibly intensifying crash severity if one occurs. Many states and UOs already have implemented policies where multiple-use poles are a normal practice that reduces crash risk while lowering ongoing costs of pole maintenance (because fewer poles are in place to maintain) (Lacy et al. 2004). Mattox (2007) investigated tree and utility pole crashes on nine urban Atlanta, GA, corridors and recommended improvements to state clear zone requirements. The study identified several factors that contribute to run-off-road crash frequency or severity, including driver fatigue or inattention, excessive vehicle speed, driving under the influence of drugs or alcohol, crash avoid- ance maneuvers, roadway conditions (such as ice, snow, or rain), vehicle component failure, and poor visibility. The study analyzed various treatment options for poles and tree hazards, including implementing the Roadside Design Guide (AASHTO 2011b) alternativesâi.e., remove the hazard, relocate the obstacle further from the road, make utility poles less rigid (breakaway poles), enhance the visibility of the objectâas well as installing roadway treatments such as edge-line rumble strips, curve delineation, skid-resistant pavements, traffic-calming measures, and pole-visibility features. The analysis concluded that collisions with trees and poles were more likely to occur within 25 feet of an intersection. Mattox (2007) recommended implemen- tation of a policy that avoids installing utility poles within 25 feet of an intersection or else places them 10 feet or more from the roadway. El Esawey and Sayed (2012) conducted a study for the British Columbia Ministry of Trans- portation and Infrastructure to assess the effects of placing utility poles at different offsets from roads in Canada. They developed a safety performance function (SPF) based on the collection of data for 1,720 km (about 1,069 miles) of roadway that accounted for 838 utility pole colli- sions on Canadian roads between 2006 through 2010. Overall, they calculated an average of approximately 0.1 collision per kilometer per year, which was very similar to the figure in the Zegeer and Parker (1983) study. The SPF values developed from this database were based on Poisson and negative binomial mode forms, which had difference prediction outcomes, and were compared with the Zegeer and Parker (1983) model for certain ADT levels and pole densities. El Esawey and Sayed (2012) found several possible reasons for these differences between the Zegeer and Parker (1983) U.S. study and their own Canadian study, including the following factors: â¢ Different samples (four U.S. states versus roads in British Columbia, Canada) â¢ Differences in driver, vehicle, and roadway characteristics between the 1980s (United States) and the early 2000s (Canada) â¢ Differences in the highway class, specifically two-lane and multilane divided and undivided roads in urban and rural areas (U.S. study) versus only rural undivided roads (Canadian study) â¢ Maturation, that is, possible changes or differences in crash reporting practices between the two studies (where reporting in British Columbia was said to also differ from crash reporting
52 Utility Pole Safety and Hazard Evaluation Approaches in other parts of Canada), with the El Esawey and Sayed (2012) nomograph for predicting utility pole crashes shown in Figure 21 â¢ Different model forms and error structures of the prediction models used in the two studies. El Esawey and Sayed (2012) developed models and nomographs that used basically the same variables as Zegeer and Parker (1983): traffic volume, pole offset, pole density, and a measure of section length, which was accounted for in the Zegeer and Parker (1983) study. El Esawey and Sayed (2012) found that increasing pole offset produced a greater effect on pole crashes than expanding pole spacing, a finding similar to that of the Zegeer and Parker study (1983). El Esawey and Sayed (2012) stated the following: The two models (Zegeer and Parkerâs and the one developed in this study) were shown to be different in terms of the type of data used in the analysis, as well as the methodological approaches employed for developing the predictive model. These two major differences explain to a great extent the dissimilarity in the estimates of the two models. Carrigan and Ray (2017) focused on the importance of the UOsâ responsibility to identify utility poles in high-risk locations and to treat those poles to reduce pole crashes. They present a series of tables and graphs that can be applied to Version 3 of the Roadside Safety Analysis Program (RSAP-V3) (Carrigan and Ray 2011), which quantifies the crash risk associated with various utility pole offsets and pole spacing distances. Carrigan and Ray (2017) explained a quantitative approach for identifying the individual poles that are at the greatest risk for a colli- sion. In particular, this approach calculates the risk for fatal and serious (A-type injury) crashes for city, county, and state roads, based first on using the RSAP-V3 and then on increasing the calculated risk of a collision with individual poles based on their location on the outside of a Figure 21. Nomograph for predicting utility pole crashes (El Esawey and Sayed 2012).
Current Countermeasure Practices 53 horizontal curve or on a grade. Carrigan and Ray (2017) stated that this approach is of most value to UOs that are interested in identifying the highest-risk poles and repositioning them to lower risk locations. Full Range of Possible Solutions and Countermeasures While the Zegeer and Parker (1983) study supplied information on expected crash effects and cost-effectiveness, other potential treatments are also available to treat poles classified as high-crash or high-risk poles. Keeping in mind that many of these deaths and injuries could be avoided, many practical solutions and countermeasures are available to address hazardously located utility poles. Some of them are summarized in the rest of this chapter. The Roadside Design Guide (AASHTO 2011b) details the following options for the safe design and siting of new utilities and the relocation of existing utility poles in hazardous locations: â¢ Increase lateral pole offset â¢ Increase pole spacing â¢ Combine pole usage with multiple utilities (joint use) â¢ Bury electric and telephone lines underground. Horne (2001) of FHWA proposed a comprehensive group of solutions and countermeasures, as follows, that can be used to address the safety problems associated with hazardously located utility poles: â¢ Keep vehicles on the roadway by employing the following methods: â Use pavement markings and delineators â Improve skid resistance and drainage â Widen lanes â Widen and pave shoulders â Straighten curves â¢ Change pole position or remove poles as follows: â Move select poles â Decrease number of poles through joint use â Decrease pole density â Increase lateral offset of poles â Increase pole spacing â Locate poles where they are less likely to be struck by vehicles (including burying lines underground) â¢ Use safety devices such as the following: â Crash cushions â Steel-reinforced safety poles â Guardrails â Concrete barriers â¢ Warn motorists of obstacles by using the following: â Pole delineation (reflective paint, sheeting, markers on poles) â Roadway lighting â Warning signs â Rumble strips.