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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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 |
|
|
|
|
TA-1 |
|
|
TA-2 |
|
|
|
|
|
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 |
|
style="border-color: #003399"
|
|
Lane closure on two-lane road using traffic signals |
|
TA-12 |
|
|
TA-13 |
|
|
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 |
|
|
|
|
|
Lane closure on minor street |
|
TA-18 |
|
|
|
Detour for one travel direction |
|
TA-19 |
|
|
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 |
|
|
|
|
|
|
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 |
|
|
|
|
style="border-color: #003399"
|
|
Lane closure on divided highway |
|
TA-33 |
|
|
|
Lane closure with barrier |
|
TA-34 |
|
|
|
Mobile operation on multilane road |
|
|
TA-35 |
|
|
|
|
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 support or trailer |
|
Channelizing device |
|
Direction of traffic |
|
Direction of temporary traffic or detour |
|
Flagger |
|
High level warning device (Flag tree) |
|
Luminaire |
|
Pavement markings that should be removed for a long term project |
|
Sign (Shown facing left) |
|
Portable concrete barrier |
|
Portable concrete barrier with warning lights |
|
Surveyor |
|
Traffic or Pedestrian signal |
|
Truck mounted attenuator |
|
Type III barricade |
|
Changeable message sign |
|
Changeable message sign support or trailer |
|
Warning light |
|
Work space |
|
Work Vehicle |
|
|