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APPENDIX A Example of Recommended Guidelines for Utility Installations and Modiï¬cations Session on Highway Rights-of-Way: Safety in the Clear Zone and Utility Installations Don L. Ivey and King K. Mak RECOMMENDED GUIDELINES Purpose The purpose of these guidelines is to enhance trafï¬c safety in practical economical ways that do not signiï¬cantly detract from the primary responsibility of utility companies, the safe transmission of power. Applicability These general guidelines are intended for use with aboveground utility facilities, includ- ing the following: 1. New utility installations, 2. Existing utility facilities that are to be relocated or adjusted within the right-of-way of highway facilities under development or construction, and 3. Existing utility facilities that are to be adjusted or relocated for safety improvements. General Guidelines The recommended general guidelines for consideration in the design and placement of aboveground utilities within the highway right-of-way are as follows: â¢ Clear recovery area: New aboveground utility installations should be located outside the clear recovery area or as far from the traveled way (or the face of the curb, if a curb is present) as practical, preferably along the right-of-way line. If a clear recovery area has 43 Don L. Ivey, Texas Transportation Institute, College Station, TX 77843. King K. Mak, 9 Cotswold Lane, San Antonio, TX 78257.
44 Utilities and Roadside Safety not been recommended by the entity responsible for the roadway, Table 1 may be used as a guide. Note that the lateral distance values in Table 1 were taken directly or inter- polated from the 1977 AASHTO Guide for Selecting, Locating, and Designing Trafï¬c Barri- ers (1), which is consistent with the 1996 Roadside Design Guide (2). In some cases, these distances are reduced when trafï¬c volumes are below 6,000 vehicles per day, as indi- cated in Figure 1. In situations in which it is necessary to locate aboveground utility facil- ities within the established clear recovery area of the highway, appropriate measures to improve trafï¬c safety should be considered, such as placing utility facilities at locations that minimize exposure to out-of-control vehicles, using breakaway or impact attenua- tion devices, or shielding vehicles from the structures with longitudinal barriers. â¢ Joint pole use: Consideration should be given to the joint use of poles within the right- of-way of roadways to the extent possible to minimize exposure of out-of-control vehicles. â¢ Span between poles: The largest feasible span between poles should be used to reduce the number of poles so as to minimize the exposure of out-of-control vehicles. â¢ Susceptible locations: Locations where aboveground utility installations are suscepti- ble to being hit by out-of-control vehicles, such as medians, trafï¬c islands, lane drops, and lane-narrowing zones, should be avoided to the extent practical. â¢ Accident experience: Consideration should be given to accident history when adjust- ing or relocating utility facilities. Appropriate safety measures to improve trafï¬c safety should be considered for locations with a signiï¬cant accident history. Examples of safety measures include placing utility facilities at locations that minimize exposure of out-of-control vehicles, using breakaway or impact attenuation devices, and shielding errant motorists from the structures with longitudinal barriers. COMMENTARY Clear Recovery Area The guidelines as described here are based principally on the concept of a clear recovery area, which is deï¬ned as âthe roadside border area, starting at the edge of the traveled way, available for safe use by errant vehiclesâ (1). New aboveground utility installations should be located outside the clear recovery area or as far from the traveled way (or the face of the curb, if a curb is present) as practical, preferably along the right-of-way line. This means, in most situations, locating aboveground utility facilities as close to the right-of-way line as practical. The term âas close as practicalâ is used because there are situations in which it may not be practical to place the utility facilities at the right-of-way line. For example, for Roadway Speed Limit (mph) Lateral Distance to Face of Poles (feet) 25 5 30 8 35 12 40 15 45 17 50 20 55 24 TABLE 1 Recommended Lateral Dimension of Clear Recovery Area Unless Constrained by Right-of-Way or Other Structures (Distance from Edge of Traveled Way to Face of Pole)
Example of Recommended Guidelines for Utility Installations and Modiï¬cations 45 poles with cross-arm structures, it is usually necessary to place the pole inside the right-of- way line to prevent the power lines from encroaching on private property. The presence of existing underground facilities, such as gas and water lines, may also preclude the place- ment of utility facilities at the right-of-way line. In situations in which aboveground utility facilities are needed within the established clear recovery area of the highway, consideration should ï¬rst be given to the feasibility of eliminating those facilities by undergrounding or by selecting alternative locations. If it is determined that the placement of utilities underground is not technically feasible or is unreasonably costly, and there are no feasible alternative locations, other appropriate measures to improve trafï¬c safety relative to utility facilities should be considered. FIGURE 1 Clear zone distance curves (2). V.P.D. = vehicles per day, A.D.T. = average daily trafï¬c. âSection 3.3.4â refers to the Roadside Design Guide.
Safety measures can be divided into two approaches. The ï¬rst approach is to reduce the probability of a vehicle collision. This approach is the one most commonly used and can be illustrated both historically and technically (3â7). The second approach is to reduce the severity of the impact when the utility is struck by an errant vehicle. These two approaches may be considered singly or in combination as dictated by the speciï¬c site conditions. Safety treatments to reduce the probability of utility facilities being struck by errant vehicles include, but are not limited to, the following: â¢ Place utility facilities at locations that are less likely to be struck by out-of-control vehi- cles (e.g., on the inside of curves instead of on the outside; on minor streets instead of on major roadways, etc.). â¢ Increase the lateral offset of utility facilities to the extent practical (e.g., use of vertical construction instead of cross-arm construction to allow poles to be placed at the right- of-way line). â¢ Reduce the number of poles through joint use or use of the largest feasible span between poles, or both. It should be pointed out that some of these safety treatments such as vertical con- struction and increasing the span between poles may necessitate using larger or taller poles. This could result in more severe impacts if such poles are struck. It is necessary to evaluate the trade-off between accident frequency and severity in these situations to ensure that safety is enhanced by such treatments. Use of Safety Structures The safety of speciï¬c utility pole installations could be improved with the use of safety structures, including breakaway devices, guardrails, and crash cushions. Similar devices have been used to improve the roadside safety of highways for over 20 years, but major improvements have been made since 1980 that render some safety structures applicable to utility installations for the ï¬rst time. The most comprehensive guide for the application of safety structures is the AASHTO Guide for Selecting, Locating, and Designing Trafï¬c Barriers (1), commonly referred to as the Barrier Guide. In most cases, the criteria for use of the three types of safety structures are consistent with the Barrier Guide. It should be noted, however, that the Barrier Guide was intended primarily for use with rural highways and may not always be directly applicable to urban roadways and streets. Also, it is important to point out that many new designs for speciï¬c structures have been developed since the Barrier Guide was published in 1977. These new designs are referenced here. Breakaway Devices A breakaway device, as applied to a utility pole to be broken away by an impacting vehi- cle, allows the vehicle to proceed on its errant path without a precipitous stop. The severed pole will then normally descend to the ground after the impacting vehicle passes through. The criteria for application of a breakaway device to a utility pole or a luminaire sup- port are as follows: â¢ The pole is within the clear recovery area as previously deï¬ned. â¢ The alternative of relocating the pole is not a practical solution because of constraints of right-of-way, roadside environment, or economics. â¢ The pole is Class 4-40 or smaller and does not have heavy devices or equipment, such as transformers or capacitor banks, attached to it. (Breakaway devices may be used on poles of material other than wood, but the pole should not be signiï¬cantly heavier or taller than a Class 4-40 timber pole.) 46 Utilities and Roadside Safety
â¢ The pole is not within a zone of signiï¬cant pedestrian activity (as deï¬ned by beneï¬tâ cost considerations). â¢ After impact by a vehicle, the ï¬nal rest position of the severed pole and dislocated con- ductors should not pose a signiï¬cant hazard to pedestrians, other vehicles, or properties in the immediate vicinity of the pole. â¢ There is a relatively safe clear recovery area beyond the breakaway pole available for the vehicle to decelerate and come to a comparatively safe stop. Location of down guy wires should be made with full consideration of their inï¬uence on impacting vehicles and the inï¬uence of loss of support for the main structure. Where down guy wires are anchored within the clear recovery area, a breakaway attachment to the guy wire should be considered to preclude the occurrence of vehicle overturn or more severe damage to the main structure. Details on breakaway attachments for down guy wires are presented elsewhere (8). In some cases, pole guys or tree guys can be ben- eï¬cial in that they are more effective in preventing a fallen pole from leaning into or falling onto the traveled way. Under most circumstances, luminaire supports within the clear recovery area should be of breakaway design. The exception to this is where a support would fall in the road- way (on or in the path of other vehicles) or where there is such exposure to pedestrians that the breakaway design would not be cost beneï¬cial. Details on breakaway designs for luminaire supports are presented elsewhere (9). Guardrails In some places, guardrails are a good choice to protect trafï¬c from a rigid utility pole or luminaire support. Guardrails function by redirecting the errant vehicle away from the pole so that the driver has a better chance of regaining control of the vehicle or coming to a comparatively safe stop. The Barrier Guide states that guardrails may be used for this purpose on the basis of engineering judgment or a cost-effectiveness study (see Table III-A-2 and the discussion on p. 21 of the Barrier Guide). The criteria for application of guardrails to shield rigid utility poles or luminaire sup- ports are as follows: â¢ The pole(s) is (are) within the clear recovery area. â¢ The alternative of relocating the poles is not a practical solution because of constraints of right-of-way, roadside environment, or economics. â¢ The installation of a guardrail over the length necessary to shield the pole(s) does not constitute a greater potential hazard to the driving public. â¢ The guardrail will not direct errant vehicles into a roadside zone of greater hazard. â¢ The face of the guardrail should not be closer than 2 ft from the edge of the traveled lane or the face of the curb. A distance of 10 ft or more is preferred, if practical. â¢ The guardrail is in a position where it will function as designed; that is, automobiles will strike the rail at speeds predominantly less than 60 mph and at angles predomi- nantly less than 25Â°. The guardrail should not be placed in a position relative to a bar- rier curb so that vehicle ramping prevents redirection. There are several factors to be considered in designing a guardrail installation. These fac- tors are discussed in Section III of the Barrier Guide and are not covered in this document. In addition to the operational guardrail systems described in the Barrier Guide (pp. 36â39), there are now several new systems with somewhat improved performance characteristics. It should be noted that the end of a guardrail can be a hazard if not designed properly. A crashworthy end treatment should be used if the guardrail terminates within the clear recovery area. In addition to the end treatments described in the Barrier Guide (pp. 50, 51), there are now several new designs available that have vastly improved performance. Details of some of the improved designs are provided elsewhere (10â12). Example of Recommended Guidelines for Utility Installations and Modiï¬cations 47
48 Utilities and Roadside Safety Crash Cushions Crash cushions protect errant vehicles from impact with a rigid utility pole or luminaire support primarily by decelerating the errant vehicle in a controlled manner and bring- ing it to a relatively safe stop before the rigid pole is reached. As stated in the Barrier Guide, crash cushions âare used to shield rigid objects or hazardous conditions that can- not be removed, relocated or made breakaway.â The use of a crash cushion may be determined on the basis of engineering judgment or a cost-effectiveness analysis. Crash cushions are more likely to be cost-effective for iso- lated hazards (e.g., a single pole with a high frequency of accident involvement) than for a pole line several hundred feet or more in length. The criteria for application of crash cushions to shield errant vehicles from a rigid util- ity pole or luminaire support are as follows: â¢ The pole is within the clear recovery area. â¢ The alternative of relocating the pole is not a practical solution because of constraints of right-of-way, roadside environment, or economics. â¢ The pole does not meet the requirements for breakaway treatment. â¢ There is sufï¬cient space in front of the rigid pole to accommodate the crash cushion without encroaching on the traveled way. â¢ The ï¬nal rest position assumed by an impacting vehicle and an impacted crash cush- ion as well as debris detached during the impact should not pose a hazard to other traf- ï¬c. â¢ The trajectory of an errant vehicle redirected by a crash cushion should be into a zone where a reasonably safe stop can be accomplished. Because of the relatively low fre- quency of vehicle impacts with utility poles, luminaire supports, or other utility struc- tures, the more sophisticated crash cushions used at sites such as ramp exit gores are unlikely to be cost-effective. Where crash cushions are determined to be a good coun- termeasure to a speciï¬c safety problem, the inertial crash cushions described in the Barrier Guide (pp. 131, 132) will probably be a better economic choice. Site-Speciï¬c Safety Considerations Some speciï¬c situations deserve special safety considerations. Brief discussions of some situations are presented here. Curves On urban arterials, especially those with crowned cross sections, consideration should be given to placing a pole line on the inside instead of on the outside of curves. As indicated in Figure 2a, poles on the outside of a curve usually have a higher exposure to vehicle impacts. This is particularly important for situations in which there is a single curve after a long straight section of roadway or in which one curve is substantially more severe than other curves in close proximity. However, for winding roadways with sequentially occur- ring curves in opposite directions, it normally would not be cost-effective for the pole line to cross the road repeatedly to achieve inside curve placement. When a pole line is placed on the inside of a severe curve (e.g., a curve with a radius of less than 1,700 ft), it may be necessary to place strain poles on the outside of the curve, as indicated in Figure 2b. These strain poles should be of a size that is adaptable to a breakaway design. Pole guys and strain poles should be used only if they can be designed in such a way that the fallen pole guy wire will not pose a hazard to trafï¬c. A preferred alternative to the use of breakaway strain poles and down guy wires is the use of a compression strut (push brace or stub pole), as indicated in Figure 2c. Lane Drops and Roadway Narrowing Placement of poles downstream of a lane drop or the area where the roadway narrows should be discouraged. This is especially important when it can be reasonably foreseen
Example of Recommended Guidelines for Utility Installations and Modiï¬cations 49 that an inattentive or physically impaired driver might not be able to accurately perceive the lane drop or lane narrowing. These situations are presented in Figures 3 and 4. Another cause of this problem is a trafï¬c conï¬ict, where a driver is prevented by another vehicle from changing lanes or moving laterally. If it is impractical to span the critical zone without a pole, consideration should be given to the use of a guardrail or crash cushion. Trafï¬c Island Placement of poles on a trafï¬c island should be strongly discouraged. Islands are an ele- ment of trafï¬c control at an intersection and are usually located within the boundaries of the traveled way. As such, they are likely to be occasionally traversed by errant vehicles. This traversal should not be prevented by a utility pole placed as indicated in Figure 5. High Exposure Side High Exposure Side High Exposure Side Low Exposure Side Low Exposure Side Low Exposure Side Main Utility Poles Main Utility PolesMain Utility Poles Compression Struts Compression Strut Down Guy Wire Down Guy Wire Down Guy Wire Down Guy Wire Down Guy Wire Strain Poles (Breakaway) Strain Pole Elevation (b) Elevation (c) Elevation (a) FIGURE 2 Location of utility poles on curves: (a) poles on outside of curve; (b) poles on inside of curve with breakaway strain poles; (c) poles on inside of curve with compression struts. FIGURE 3 Exposure of vehicle to utility pole downstream of lane drop.
50 Utilities and Roadside Safety FIGURE 5 Inappropriate location of poles within a trafï¬c island or median. If placement of a utility pole on an island is a practical necessity, consideration should be given to protecting errant vehicles with a crash cushion. Medians Placement of poles in medians, as indicated in Figure 5, should be strongly discouraged. Medians are safeguards against head-on collisions and, as such, provide space for errant vehicles to regain control or space for installation of median barriers. A pole or pole line in a median should be considered only if vehicles can be completely shielded from the poles by median barriers. Luminaires are often placed in protected positions on top of median barriers. Use of Existing Safety Structures Where guardrails, bridge rails, and crash cushions exist, consideration should be given in pole placement to take advantage of the shielding inï¬uence of these structures. An example is presented in Figure 6. During new highway or street construction, coordina- tion of safety structure design and utility facility design should be pursued to reduce the inï¬uence of unshielded poles. Trafï¬c Conï¬icts Where critical trafï¬c conï¬icts can be foreseen, especially at intersections of high-speed roadways, pole placement may be designed to avoid the most critical secondary colli- sions. For example, if the major roadway is in a northâsouth direction and the minor roadway is eastâwest, the most critical quadrants for a secondary collision (collision of a vehicle with a pole after an initial two-vehicle collision) are the northeast and southwest quadrants. Thus, the preferred placement for poles at this intersection would be in the northwest and/or southeast quadrants, as indicated in Figure 7. FIGURE 4 Placement of pole downstream of roadway narrowing.
Example of Recommended Guidelines for Utility Installations and Modiï¬cations 51 REFERENCES 1. Guide for Selecting, Locating, and Designing Trafï¬c Barriers. AASHTO, Washington, D.C., 1977. 2. Roadside Design Guide. AASHTO, Washington, D.C., 1996. 3. A Policy on the Accommodation of Utilities Within Highway Right-of-Way. AASHTO, Washington, D.C., 1981. 4. Highway Design and Operational Practices Related to Highway Safety, 2nd ed. Select Subcommit- tee on Highway Safety, AASHTO, Washington, D.C., 1974. 5. A Policy on Geometric Design of Highways and Streets. AASHTO, Washington, D.C., 1984. 6. Accommodation of Utilities. 23 CFR Part 645, Subpart B, U.S. Department of Transportation, FHWA, Washington, D.C., May 1985. 7. Manual of Uniform Minimum Standards for Design, Construction and Maintenance for Streets and HighwaysâState of Florida. Florida Department of Transportation, Tallahassee, 1986. 8. Ivey, D. L., and J. R. Morgan. Safer Timber Utility Poles, Vol. 1. Final Report for Contract No. DTFH61-83-C-00009, FHWA, Texas Transportation Institute, Texas A&M University System, College Station, June 1985. 9. Standard Specifications for Structural Supports of Highway Signs, Luminaires and Traffic Signals. AASHTO, Washington, D.C., 1975. FIGURE 7 Intersection zones having highest exposure to secondary collisions. FIGURE 6 Pole shielded from trafï¬c by an existing guardrail.
10. New Guardrail End Treatment. Study No. 2-8-86-404. Texas State Department of Highways and Public Transportation, Texas Transportation Institute, Texas A&M University System, College Station, 1986. 11. Bronstad, M. E., J. B. Meyer, and L. Meczkowski. Guardrail and Median Barrier Terminals for Mini- Size Cars. Report FHWA/RD-85/062. FHWA, U.S. Department of Transportation, Washing- ton, D.C., May 1985. 12. W-Beam Guardrail End Treatments. FHWA Technical Advisory T5040.25. FHWA, U.S. Depart- ment of Transportation, Washington, D.C., Jan. 1986. 52 Utilities and Roadside Safety