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Section 7: Pole Placement Guidelines

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Introduction

This section contains guidelines for the placement of conventional lighting poles in relation to other roadway elements. These guidelines apply to all designated routes, whether the poles are installed by construction contract, state forces, municipalities, or others.

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Clear Zone

This section contains references to the “ clear zone” (also called the clear recovery area). The clear zone is provided along highways to allow vehicles veering off the travel lane opportunity for safe recovery or stopping. The clear zone width (always measured from the edge of the travel lane) depends on several factors, including:

  • whether the surrounding area is rural or urban
  • the functional classification of the highway
  • the design speed
  • average daily traffic (ADT).

The Roadway Design Manual contains a full discussion of the clear zone (Chapter 2, Section 6, Subheading: “ Horizontal Clearance to Obstructions”) and provides the minimum and desirable widths for various roadways.

NOTE: Light poles should be offset at least 2.5 feet from the curb face, even if the clear zone is 1.5 feet. All pole offset dimensions shown in this section are measured to the pole centerline.

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House Side vs. Median Mounting

“House side mounting” refers to the placement of luminaires between the curb and right-of-way line.

“Median mounting” refers to placement on open medians or medians with concrete traffic barrier.

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Two Types of Poles

There are two types of poles used for conventional lighting: “non-breakaway” and “breakaway.” Non-breakaway poles are rigidly mounted, usually remaining upright when hit by a vehicle. Breakaway poles (described in Chapter 5, Section 4, under the heading Breakaway Support) are designed so that the base will shear easily on impact. The following table briefly explains the advantages and disadvantages of both types when struck by an errant vehicle.

Anchor: #i1002938Breakaway and Non-breakaway poles — Pros and Cons

Type of Pole

Advantage

Disadvantage

Non-Breakaway

Normally does not fall down and cause further damage to sur-rounding people and property.

Likelihood of greater injury to occupants and damage to vehicle.

Breakaway

Less likelihood of damage to impacting vehicle and injury to occupants.

Falling pole may be hazard to sur-rounding pedestrians, traffic, or property.



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Breakaway Poles Preferred

Because of their respective advantages and disadvantages, both types of poles have appropriate uses. However, unless special circumstances exist, breakaway poles are preferred over the non-breakaway type.

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When Not To Use Breakaway Poles

Circumstances that would preclude the use of breakaway poles include situations where they are more hazardous than a non-breakaway poles and situations in which the breakaway feature would be useless. Breakaway poles are not normally used if:

  • substantial pedestrian traffic is a consideration in the area
  • a falling pole could cause more damage than that caused by an automobile striking a rigid pole
  • overhead electric lines are too close
  • the pole is mounted atop a concrete traffic barrier
  • the pole is mounted behind a metal beam guard fence (see following discussions on “Protection of Non-Breakaway Poles” and “Placement of Non-Breakaway Poles”).

Other considerations frequently come into play. The preceding list is provided only as an overview.

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Protection of Non-breakaway Poles

When a non-breakaway pole is used inside the clear zone, it must be protected from traffic. Acceptable methods of protection include mounting the pole:

  • on a concrete traffic barrier
  • behind a metal beam guard fence or other non-yielding structure.

Curbs are not considered adequate protection for non-breakaway poles.

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Placement of Non-breakaway Poles

Generally, non-breakaway roadway lighting poles may be used on the house side of roadways when placed outside of the clear zone or inside the clear zone when protected from impact.

Non-breakaway poles should be placed as close to the right-of-way line as lighting design and practicality permit. Wherever possible, non-breakaway poles should be placed among other nonyielding structures, to minimize the hazard.

If non-breakaway poles are used and are not protected, the poles must be outside the clear zone and as close to the right-of-way line as possible subject to good lighting design practice.

Non-breakaway poles mounted behind metal beam guard fence should be placed at least 2.5 feet behind the guard fence.

Remember, joint usage of poles is encouraged to reduce roadside clutter and the number of fixed objects along the roadside. When lighting is provided at signalized intersections and when conditions permit, the luminaires should be mounted on the traffic signal pole. Note that luminaires mounted on traffic signal poles should be powered from the signal electrical service.

Luminaires mounted on traffic signal poles should be oriented so that they are perpendicular to the centerline of the roadway being lighted.

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Falling Area for Breakaway Poles

To understand the use and placement of breakaway poles, it is important to understand the concept of “falling area.” Research shows that most errant vehicles striking light poles are traveling at an angle less than 20 degrees from their original path and that light poles fall within one mounting height from the foundation along the direction of vehicle travel. A breakaway pole falls within 2/5 (40 percent) of its mounting height in a direction perpendicular to and away from the lane in which the errant vehicle was traveling (see Figure 6-7, Falling area — final position of 50 feet luminaire support.) Therefore, to prevent knocked down poles from encroaching onto other traffic lanes, breakaway poles should be placed so that they have a falling area of at least 2/5 of the mounting height behind the poles and one mounting height on the side of the pole.

 Falling area — final position
of 50 feet luminaire support. (click in image to see full-size image) Anchor: #i1000216grtop

Figure 6-7. Falling area — final position of 50 feet luminaire support.

EXAMPLE: In Figure 6-7, the falling area is calculated as follows:

2/5 × 50 ft. mounting height = 20 ft. falling area

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Use and Placement of Breakaway Poles

Unprotected roadway lighting poles located inside the clear zone should be breakaway, unless conditions dictate otherwise.

Breakaway poles placed on the house side of interstate highways should be 15 feet from lane edge and should provide a clearance behind the pole of 2/5 of the mounting height. For highways other than interstates, breakaway poles placed on the house side of travel lanes should be 15 feet from lane edge where practical. If sufficient right-of-way does not exist for this clearance, the poles may be placed just inside the right-of-way line but not closer than 2.5 feet from lane edge.

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House Side Lighting

For house side lighting, the poles should be located as far from the shoulder edge as practicable. Generally, the minimum should be 15 feet from the lane edge.

shows typical house side lighting of a controlled access roadway with a median less than 30 feet wide. If the median width were 30 feet or greater, then median lighting could be used.

 Typical house-side lighting for controlled
access highway.  In this example: Luminaires are 250 watt high pressure
sodium (HPS). — Mounting Height is 40 feet. — Spacing varies
(see Section 6 of this chapter, “Spacing of Light Poles”). (click in image to see full-size image) Anchor: #i1000228grtop

Figure 6-8. Typical house-side lighting for controlled access highway. In this example: Luminaires are 250 watt high pressure sodium (HPS). — Mounting Height is 40 feet. — Spacing varies (see Section 6 of this chapter, “Spacing of Light Poles”).

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Median Lighting

Breakaway poles placed in medians should not be closer than 2/5 of the mounting height from either main lane edge. Breakaway poles should not be placed in medians less than 30 feet wide, except as noted in the following paragraph.

Median lighting in narrow medians should be avoided. If no other alternative is possible, an exception may be made for divided city streets with curbed medians, speed limit of 45 MPH or less, and where pedestrian traffic allows the use of breakaway poles. In this situation, breakaway poles may be used if placed at least 2.5 feet from any curb face, the pole height should not exceed 30 feet and pole mast arm lengths should not exceed 4 feet. Light poles should not be installed in urban median areas less than 30 feet wide if any other design is practical.

The turning lane of a divided city street may be included as part of the median width when determining the falling area. Remember, though, 2.5 feet offset from curb face should be maintained.

Breakaway poles placed in city street medians should also be placed at least one mounting height back from the end of the median at intersections.

Non-breakaway poles should not be placed in medians unless properly protected.

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Median Lighting Design Examples

The following illustrations show typical median lighting designs for various controlled access roadway sections.

Example 1 — Unprotected Median: Figure 6-9 shows a typical median lighting design for a controlled access roadway having an unprotected median 30 feet or greater in width. Here breakaway poles should be used.

 Median lighting with breakaway poles. (click in image to see full-size image) Anchor: #i1000240grtop

Figure 6-9. Median lighting with breakaway poles.

NOTE: Where median width exceeds 60 feet , it may be necessary to treat each main lane as a separate roadway, using two rows of poles in the median or house side (see Figure 6-8 for illustration of house side lighting).

Example 2 — Concrete Median Barrier: Figure 6-10 shows a typical median lighting design for a controlled access roadway having a concrete median barrier. Median width in this situation is typically 20 feet.

 Median lighting with concrete median barrier. (click in image to see full-size image) Anchor: #i1000244grtop

Figure 6-10. Median lighting with concrete median barrier.

The following table shows the recommended lighting for concrete median barriers.

Anchor: #i1002954Recommended Lighting for Concrete Median Barriers

Number of Lanes

Luminaires

Mounting Height

Spacing

2 or 3 each direction

250 watt HPS

40 feet

varies

4 or 5 each direction

400 watt HPS

50 feet

varies



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Avoid Channelizing Islands

Avoid placing lighting poles in channelizing (dividing) islands, as the falling area of the pole is difficult to obtain except in cases where the island is very large.

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Breakaway Pole Placement Examples

Figure 6-11 and Figure 6-12 show examples of breakaway pole placement and respective minimum applicable distances recommended for each of the cases listed in the following table.

Anchor: #i1002973Breakaway Pole Placement Cases

Case No.

Case

Shown in

1.

Median-mounted poles or poles inside the clear zone of two separate roadways.

Figure 6-11

2.

Outside clear zone of frontage road but inside the clear zone of main lanes.

Figure 6-11

3.

Outside clear zone of main lane but inside clear zone of frontage road.

Figure 6-11

4.

Minimum distance from ramp.

Figure 6-11

5.

House side of frontage road.

Figure 6-11

6.

Minimum distance from overhead electric lines (OHE).

Figure 6-11

7.

City street intersection.

Figure 6-12



 Controlled access facility illustrating
example Cases 1 through 6.  Minimum distances (designated here by
the letters “A” through “G”)
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Figure 6-11. Controlled access facility illustrating example Cases 1 through 6. Minimum distances (designated here by the letters “A” through “G”) are shown in the following table.

Anchor: #i1003009Minimum Distances

(Indicated by Letter in 6-11 and Figure 6-12)

A.

2/5 (40%) of one mounting height from edge of travel lane.

B.

15 feet from edge of travel lane (20 feet desirable).

C.

Depends on whether or not the roadway is curbed or uncurbed and on the design speed (see following table).

Pole Offset from Roadway

 

 

Distance from Curb Face or Lane Edge

Lane Edge

Design Speed

Desirable

Minimum

Barrier Curb*

45 mph or lower

10 ft.

2.5 ft.**

Barrier Curb*

50 mph or higher

20 ft.

15 ft.**

Uncurbed

40 mph or lower

15 ft.

10 ft.**

Uncurbed

45 mph or higher

20 ft.

15 ft.**

* Curbed roadway denotes a roadway with a 6 inch minimum barrier-type curb. All mountable-type curb is considered as uncurbed.

** or as near ROW line as practicable.

D.

One mounting height.

E.

20 feet, or as required by utility company.

F.

8 feet, or as required by utility company.

G.

Clear zone.


 Example Case 7.  Minimum distances (designated
by letters) are shown in the preceding table. (click in image to see full-size image) Anchor: #OJNILLMFgrtop

Figure 6-12. Example Case 7. Minimum distances (designated by letters) are shown in the preceding table.

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Minimum Values

The distances shown and described in these guidelines as well as the clear zone definitions are minimum values. Even though breakaway poles may be placed in the clear zones, both breakaway and non-breakaway lighting poles should be placed as far away from the roadway as practical while maintaining the required light levels.

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Poles in Sidewalks

The Americans with Disabilities Act (ADA) accessibility guidelines (36 CFR, Part 1191) stipulate that public sidewalks, where provided, must contain a continuous passage at least 36 inches wide. For this reason, the placement of poles in sidewalks should be avoided. Where such placement cannot be avoided, the sidewalk may need to be widened around the pole to maintain the required passage.

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Foundation Height

Foundations for luminaire supports should be set flush with the ground line. Foundations placed on slopes should have the edge closest to the travel lanes flush with the ground.

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Striking Height

Tests have shown that breakaway luminaire supports may not operate properly when the vehicle strikes the pole too high above the ground. Breakaway poles should, therefore, not be placed in areas where they are likely to be struck more than 28 inches above the top of the foundation. Limiting the negative side slopes to 1:6 between roadway and luminaire supports should ensure acceptable striking height.

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Breakaway Pole Frangibility

Chapter 9, Section 3, Breakaway Light Poles, provides a discussion of the frangibility requirements for breakaway poles.

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