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6H. APPLICATION OF DEVICES

6H-1. TYPICAL APPLICATIONS

Section 6G contains discussions of typical activities. Section 6H presents typical application diagrams for a variety of situations commonly encountered. While not every situation is addressed, the procedures illustrated can generally be adapted to a broad range of conditions. In many instances, it will be necessary to combine features from various typical application diagrams. For example, work at an intersection may present a near-side work area for one street and a far-side work area for the other street.

These treatments are found in two different diagrams, and a third diagram shows how to handle pedestrian crosswalk closings.

Procedures for establishing temporary traffic control zones vary with such conditions as road configuration, location of the work, work activity, duration, traffic speed, traffic volume, and pedestrians. Examples presented in this chapter are guides showing how to apply principles and standards. Judgment is needed in applying these guidelines to actual situations and adjusting to field conditions. In general, the procedures illustrated represent the minimum needs for the situation depicted. Other devices may added to supplement the devices and device spacing may be adjusted to provide additional reaction time or protection. Where the situation being addressed is less than typical, actual conditions may require fewer devices.

6H-2. GENERAL NOTES

General notes for various application categories are provided below. Numerous figures and tables found throughout part VI provide guidance for the development of traffic control plans and procedures. Several of these exhibits presented in previous chapters are repeated for convenience after the general notes. Note particularly figure VI-11, which serves as the legend for symbols used in the diagrams.

  1. Work Performed on the Roadside (Outside Shoulder)

    When work is being performed off the roadway (beyond shoulder yet within the right-of-way), little or no temporary traffic control may be needed. If there is no effect upon traffic, no devices are needed, but this is rarely the case. More commonly, there may be driver distraction, vehicles may be parked on the shoulder, vehicles may be accessing the work site via the highway, or equipment may on occasion need to travel on or cross the roadway to perform the work operation (e.g., mowing). Where these situations pertain, a single warning sign, such as ROAD WORK AHEAD will generally suffice.

    If vehicles are using the shoulder, a SHOULDER WORK sign is appropriate. For mowing operations, the sign MOWING AHEAD may be used. Where the activity is spread out over a distance of more than 2 miles, the sign should be repeated every 2 miles. A supplementary plate with the message NEXT [X] MILES may be placed below the initial warning sign.

  2. Work Performed on Shoulders

    When a highway shoulder is occupied, warning is needed to advise the driver and protect the workers. As a minimum, the single warning sign SHOULDER WORK is adequate. When work is performed on a paved shoulder 8 or more feet wide, a transition area is needed in which channelizing devices are placed on a taper of length that conforms to the requirements of a shoulder taper. When paved shoulders of width of 8 feet or more are closed on freeways and expressways, additional treatment is generally needed to alert traffic to the possibility of a disabled vehicle that cannot get off the traveled way. An initial general warning sign is needed (e.g., ROAD WORK AHEAD), followed by a RIGHT or LEFT SHOULDER CLOSED sign. Where the end of the shoulder closure extends beyond the distance that can be perceived by motorists, a supplementary plate bearing the message NEXT [X] FEET (or MILES) should be placed below the SHOULDER CLOSED sign.

    When the shoulder is not occupied but work has adversely affected its condition, the LOW SHOULDER or SOFT SHOULDER sign should be used, if appropriate. Where the condition extends over a distance in excess of 1 mile, the sign should be repeated at 1-mile intervals. In addition, a supplementary plate bearing the message NEXT [X] MILES may be placed below the first such warning sign.

    On multilane, divided highways, signs advising of shoulder work or the condition of the shoulder should be placed only on the side of the affected shoulder.

  3. Mobile and Short-Duration Operations

    As compared to stationary operations, mobile and short-duration operations are distinct activities that may involve different treatments. More mobile devices are needed (e.g., signs mounted on trucks), and larger, more imposing, and more visible devices can be used effectively and economically. For example, appropriately colored and marked vehicles with flashing or rotating lights, perhaps augmented with signs or arrow displays, may be used in place of signs and channelizing devices. The trade-off is economical because work duration is short. Mobility is essential, the crew is always onsite, and some of the vehicles may be required for the work activity or crew transportation. Safety is not compromised, as numerous small devices are merely replaced by fewer, more dominant and effective devices.

    (1) Short Duration

Short-duration activities are generally considered to be those in which it takes longer to set up and remove the traffic control zone than to perform the work. Typically, such operations can be accomplished in 60 minutes or less.

There are hazards involved for the crew in setting up and taking down a traffic control zone. Also, as the work time is short, the time during which motorists are affected is significantly increased when additional devices are installed and removed. Considering these factors, it is generally held that simplified control procedures are warranted for short-duration activities. Such shortcomings may be offset by the use of other, more dominant devices, such as special lighting units on work vehicles.

(2) Mobile Operations

Mobile operations include activities that stop intermittently and then move on (e.g., pothole patching and litter pickup) and those that move continuously (e.g., pavement striping).

With operations that move slowly (less than 3 mph), it may be feasible to use stationary signing that is periodically retrieved and repositioned in the advance warning area. At higher speeds, trucks are typically used as components of the traffic control zones. Appropriately colored and marked vehicles with signs, flashing or rotating lights, and special lighting panels move as part of a train behind the work vehicles.

Mobile operations that move at speeds greater than 20 mph, such as snowplowing operations, shall have appropriate devices on the equipment, (i.e., rotating lights, signs, or special lighting) or shall use a protection vehicle with appropriate warning devices.

  1. Lane Closings on Two-Lane Roads

    When one lane of a two-lane road is closed, the remaining lane must accommodate both directions of travel. The typical procedure for short-term work is to utilize flaggers to alternate traffic flow, as shown in figure TA-10. For long-term operations, a temporary traffic signal, as shown in figure TA-12, is an alternative. For low traffic volumes on a minor road, where traffic may be self-regulating, the procedure illustrated in figure TA-11 may be used.

  2. Lane Closings on Multilane Roads

    When a lane is closed on a multilane road, a transition area containing a merging taper is needed. Typically, the advance warning area contains three warning signs, such as ROAD WORK AHEAD RIGHT or LEFT LANE CLOSED AHEAD, and the Lane Reduction Transition sign.

    When an interior lane is closed for use as a work space, consideration should be given to closing an adjacent lane also. This procedure provides additional space for vehicles and materials and facilitates the movement of equipment within the work space. On multilane undivided roads and streets where the left lane is closed, such additional space can be obtained by also closing the left lane in the opposing direction.

  3. Work Performed in the Vicinity of Intersections

    The typical application diagrams contained herein depict typical urban intersections on arterial streets. Where the posted speed, the off-peak 85th percentile speed prior to work starting, or the anticipated speed of traffic equals or exceeds 45 mph, additional warning signs may be needed in the advance warning area.

    The typical application diagrams for intersections are classified according to the location of the work space with respect to the intersection area (as defined by the extension of curb or edge lines.) Thus, there are three classifications-near-side, far-side and in-the-intersection.

    Traffic control zones in the vicinity of intersections may block movements and interfere with normal traffic flows. Such conflicts frequently occur at complex signalized intersections having such features as traffic signal heads over particular lanes, lanes allocated to specific movements, multiple signal phases, and signal detectors for actuated control. Where such potential problems exist, the traffic engineering staff having jurisdiction should be contacted.

    It should be recognized that some work spaces may extend into more than one portion of the intersection. For example, work in one quadrant may create a near-side work space on one street and a far-side work space on the cross street. In such instances, the traffic control zone should incorporate features shown in two or more of the intersection and pedestrian typical application diagrams shown herein.

(1) Work Space on the Near Side of Intersections

Near-side work spaces, as depicted in figure TA-21, are simply handled as a mid-block lane closure. Where space is restricted, as with short block spacings, two warning signs may be used in the advance warning area, and a third "action-type" warning or regulatory sign (e.g., KEEP LEFT) is placed within the transition area. The one significant problem that may occur with a near-side lane closure is a reduction in capacity, which during certain hours of operation could result in congestion and backups.

(2) Work Space on the Far Side of Intersections

Far-side work spaces require additional treatment because motorists typically may enter the activity area by straight-through and left- or right-turning movements. Merging movements within the intersection should be avoided. Therefore, the applicable principle is to close any lanes on the near-side intersection approach that do not carry through the intersection as lanes shown in figures TA-22, TA-23, TA-24, and TA-25. If, however, there is a significant number of vehicles turning from this lane, then it may be advantageous to convert the lane to an exclusive turn lane.

(3) Work Space Within the Intersection

Figures TA-26 and TA-27 provide guidance as to applicable procedures for work performed within the intersection. When directing traffic within the intersection, consideration should be given to using a uniformed police officer.

  1. Incident Management Situations

    The immediate response to an emergency situation must by necessity make use of available devices and equipment. Given the opportunity, however, longer term emergencies should be treated in a manner similar to other temporary traffic control work sites.

  2. Features That May Be Added to the Diagrams

    The measures described below are useful in increasing conspicuity and visibility of traffic control devices.

(1) Flags on Signs

Flags may be placed above signs to enhance their target value and increase motorists' awareness. Flags are useful for daytime operations only.

(2) Flashing Lights on Signs

Portable warning lights may be placed above signs to enhance their target value and increase motorists' awareness. Type A low-intensity warning lights are effective at night. Type B high-intensity warning lights are effective for both day and night.

(3) Sign Illumination

The retroreflective material used on sign faces returns light to a light source. In some instances, vehicular headlight beams may not illuminate a sign, such as those placed on sharp curves or on crossroads. Likewise, some road users, such as pedestrians and cyclists, may have inadequate head lamps or no head lamps at all. When these situations are encountered, adequate nighttime sign visibility may be obtained using internal or external sign illumination.

(4) Lights on Channelizing Devices

For intermediate and long-term operations, consideration should be given to placing portable warning lights on channelizing devices. Lights are especially effective in the following applications: where new travel patterns are established at tapers, shifts, and runarounds; at road closings; on devices placed on horizontal and vertical curves; where headlights may not adequately illuminate retroreflective material on channelizing devices; and when adverse weather conditions are anticipated.

6H-3. TYPICAL APPLICATION DIAGRAMS

Table VI-4 is an index of typical applications diagrams. The remainder of the chapter contains the typical application diagrams on the right page with notes on the facing page to the left. The legend for the symbols used in the diagrams is provided as figure VI-12.

In many of the diagrams, sign spacings are indicated by letters using criteria set forth in section 6F-1. Table VI-3 in that section provides sign spacing dimensions for various area and road types. The table is repeated on the next page for ease of reference.

Table VI-3. Suggested advance warning sign spacing

Road type Distance between signs
A B C
Urban (low speed*) 200 200 200
Urban (high speed*) 350 350 350
Rural 500 500 500
Expressway/Freeway 1,000 1,600 2,600

Formulas for L**
SPEED FORMULA
40 mph or less L = WS2/60
45 mph or greater L = W x S


* Speed category to be determined by State highway agency in cooperation with local jurisdictions.
** L = Taper length in feet
W = Width of offset in feet
S = Posted speed, the off-peak 85th percentile speed prior to
work starting, or the anticipated operating speed in mph.

Table VI-4. Index to typical application diagrams

Location
Roadway Type
Application
Duration of work
Stationary/*
short duration***
Mobile**
Roadside (outside of shoulder)
All roadways
Work beyond the shoulder
TA-1
Blasting Zone
TA-2
Shoulder
All roadways
Work on shoulders
TA-3
Mobile operation on shoulder
TA-4
Shoulder closed on freeway
TA-5
Shoulder work with minor encroachment
TA-6
Within traveled way
Rural two-lane
Road closed with on-site detour
TA-7
Roads closed with off-site detour
TA-8
Roads open and closed with detour
TA-9
Lane closure on two-lane road using flaggers
TA-10
Lane closure on low-volume, two-lane road
TA-11
Lane closure on two-lane road using traffic signals
TA-12
Temporary road closure
TA-13
Haul road crossing
TA-14
Work in center of low-volume roads
TA-15
Surveying along centerline of low-volume road
TA-16
Mobile operation on two-lane road
TA-17
Urban Streets
Lane closure on minor street
TA-18
Detour for one travel direction
TA-19
Detour for closed street
TA-20
Intersections and walkways
Lane closure near side of intersection
TA-21
Right lane closure far side of intersection
TA-22
Left lane closure far side of intersection
TA-23
Half road closure far side of intersection
TA-24
Multiple lane closures at intersection
TA-25
Closure in center of intersection
TA-26
Closure at side of intersection
TA-27
Sidewalk closures and bypass walkway
TA-28
Sidewalk closures and pedestrian detours
TA-29
Multilane undivided
Interior lane closure on multilane street
TA-30
Lane closure with uneven directional on streets volume
TA-31
Half road closure on multilane highway
TA-32
Multilane divided
Lane closure on divided highway
TA-33
Lane closure with barrier
TA-34
Mobile operation on multilane road
TA-35
Freeways
Lane shift on freeway
TA-36
Double lane closure on freeway
TA-37
Interior lane closure on freeway
TA-38
Median crossover on freeway
TA-39
Median crossover for entrance ramp
TA-40
Median crossover for exit ramp
TA-41
Work in vicinity of exit ramp
TA-42
Partial exit ramp closure
TA-43
Work in vicinity of entrance ramp
TA-44

* Long-term stationary: more than 3 days; Intermediate-term
stationary: overnight up to 3 days; Short-term stationary:
anytime, more than 60 minutes.
** Mobile: Intermittent and continuous moving.
*** Short-duration: up to 60 minutes.

Arrow panel Arrow panel
Arrow panel support or trailer Arrow panel support or trailer
Channelizing device Channelizing device
Direction of traffic Direction of traffic
Direction of temporary traffic or detour Direction of temporary traffic or detour
Flagger Flagger
High level warning device (Flag tree) High level warning device (Flag tree)
Luminaire Luminaire
Pavement markings that should be removed for a long term project Pavement markings that should be removed for a long term project
Sign (Shown facing left) Sign (Shown facing left)
Portable concrete barrier Portable concrete barrier
Portable concrete barrier with warning lights Portable concrete barrier with warning lights
Surveyor Surveyor
Traffic or Pedestrian signal Traffic or Pedestrian signal
Truck mounted attenuator Truck mounted attenuator
Type III barricade Type III barricade
Changeable message sign Changeable message sign
Changeable message sign support or trailer Changeable message sign support or trailer
Warning light Warning light
Work space Work space
Work vehicle Work vehicle

Figure VI-11. Symbols used in typical application diagrams.