Chapter 6F. Temporary Traffic Control Zone Devices
Section 6F.69 Temporary Raised Islands
Standard:
Temporary raised islands shall be used only in combination with
pavement striping and other suitable channelizing devices.
Option:
A temporary raised island may be used to separate vehicular traffic
flows in two-lane, two-way operations on roadways having a vehicular
traffic volume range of 4,000 to 15,000 average daily traffic (ADT)
and on freeways having a vehicular traffic volume range of 22,000
ADT to 60,000 ADT.
Temporary raised islands also may be used in other than two-lane, two-way operations where physical separation of vehicular traffic from the TTC zone is not required.
Guidance:
Temporary raised islands should have the basic dimensions of 100
mm (4 in) high by at least 450 mm (18 in) wide and have rounded
or chamfered corners.
The temporary raised islands should not be designed in such a manner that they would cause a motorist to lose control of the vehicle if the vehicle inadvertently strikes the temporary raised island. If struck, pieces of the island should not be dislodged to the extent that they could penetrate the occupant compartment or involve other vehicles.
Standard:
At pedestrian crossing locations, temporary raised islands shall
have an opening or be shortened to provide at least a 1500 mm (60
in) wide pathway for the crossing pedestrian.
Section 6F.70 Opposing Traffic Lane Divider
Support:
Opposing traffic lane dividers are delineation devices used as center
lane dividers to separate opposing vehicular traffic on a two-lane,
two-way operation.
Standard:
Opposing traffic lane dividers shall not be placed across pedestrian
crossings.
The Opposing Traffic Lane Divider (W6-4) sign (see Figure 6F-4, Sheet 2 of 4) is an upright, retroreflective orange-colored sign placed on a flexible support and sized at least 300 mm (12 in) wide by 450 mm (18 in) high.
Section 6F.71 Pavement Markings
Standard:
The provisions of this Section shall not be considered applicable
for short-term, mobile, or incident management TTC zones.
Pavement markings shall be maintained along paved streets and highways in all long- and intermediate-term stationary (see Section 6G.02) TTC zones. All pavement markings shall be in accordance with Chapters 3A and 3B, except as indicated in Section 6F.72. Pavement markings shall match the markings in place at both ends of the TTC zone. Pavement markings shall be placed along the entire length of any surfaced detour or temporary roadway prior to the detour or roadway being opened to road users.
Warning signs, channelizing devices, and delineation shall be used to indicate required road user paths in TTC zones where it is not possible to provide a clear path by pavement markings. All pavement markings and devices used to delineate road user paths shall be carefully reviewed during daytime and nighttime periods.
For long-term stationary operations, pavement markings in the temporary traveled way that are no longer applicable shall be removed or obliterated as soon as practical. Pavement marking obliteration shall leave a minimum of pavement scars and shall remove old marking material. Painting over existing pavement markings with black paint or spraying with asphalt shall not be accepted as a substitute for removal or obliteration.
Guidance:
Road users should be provided pavement markings within a TTC zone
comparable to the pavement markings normally maintained along such
roadways, particularly at either end of the TTC zone.
The intended vehicle path should be defined in day, night, and twilight periods under both wet and dry pavement conditions.
The work should be planned and staged to provide for the placement and removal of the pavement markings.
Markings should be provided in intermediate-term stationary work zones.
Option:
Removable, nonreflective, preformed tape may be used where markings
need to be covered temporarily.
Section 6F.72 Temporary Pavement Markings
Support:
Temporary pavement markings are those that are allowed to remain
in place until the earliest date when it is practical and possible
to install pavement markings that meet the Part 3 standards for
pavement markings.
Guidance:
Temporary pavement markings should not be in place for more than
2 weeks unless justified by an engineering study.
Standard:
All temporary pavement markings, including pavement markings for
no-passing zones, shall conform to the requirements of Chapters
3A and 3B. All temporary broken-line pavement markings shall use
the same cycle length as permanent markings and be at least 0.6
m (2 ft) long.
Option:
Half-cycle lengths with a minimum of 0.6 m (2 ft) stripes may be
used on roadways with severe curvature (see Section
3A.05) for centerlines in passing zones and for lane lines.
For temporary situations of 3 calendar days or less, for a two- or three-lane road, no-passing zones may be identified by using DO NOT PASS (R4-1), PASS WITH CARE (R4-2) and NO PASSING ZONE (W14-3) signs (see Sections 2B.29, 2B.30, and 2C.35) rather than pavement markings. Also, DO NOT PASS, PASS WITH CARE and NO PASSING ZONE signs may be used instead of pavement markings on roads with low volumes for longer periods in accordance with the State's or highway agency's policy.
Guidance:
If used, the DO NOT PASS, PASS WITH CARE, and NO PASSING ZONE signs
should be placed in accordance with Sections 2B.29, 2B.30, and 2C.35.
The temporary use of edge lines, channelizing lines, lane reduction transitions, gore markings, and other longitudinal markings, and the various nonlongitudinal markings (such as stop lines, railroad crossings, crosswalks, words or symbols) should be in accordance with the State's or highway agency's policy.
Section 6F.73 Raised Pavement Markers
Standard:
If raised pavement markers are used to substitute for broken line
segments, at least two retroreflective markers shall be placed,
one at each end of a segment of 0.6 to 1.5 m (2 to 5 ft) in length.
For segments longer than 1.5 m (5 ft), a group of at least three
retroreflective markers shall be equally spaced at no greater than
N/8 (see Section 3B.11).
The value of N for a broken or dotted line shall equal the length
of one line segment plus one gap. The value of N referenced for
solid lines shall equal the N for the broken or dotted lines that
might be adjacent to or might extend the solid lines (see Sections
3B.13
and 3B.14).
Guidance:
Raised pavement markers should be considered for use along surfaced
detours or temporary roadways, and other changed or new travel-lane
alignments.
Option:
Retroreflective or internally illuminated raised pavement markers,
or nonretroreflective raised pavement markers supplemented by retroreflective
or internally illuminated markers, may replace or supplement markings
prescribed in Chapters 3A and 3B.
Section 6F.74 Delineators
Standard:
When used, delineators shall combine with or supplement other TTC
devices. They shall be mounted on crashworthy supports so that the
reflecting unit is approximately 1.2 m (4 ft) above the near roadway
edge. The standard color for delineators used along both sides of
two-way streets and highways and the right side of one-way roadways
shall be white. Delineators used along the left side of one-way
roadways shall be yellow.
Guidance:
Spacing along roadway curves should be as set forth in Section
3D.04 and should be such that several delineators are always
visible to the driver.
Option:
Delineators may be used in TTC zones to indicate the alignment of
the roadway and to outline the required vehicle path through the
TTC zone.
Section 6F.75 Lighting Devices
Guidance:
Lighting devices should be provided in TTC zones based on engineering
judgment.
When used to supplement channelization, the maximum spacing for warning lights should be identical to the channelizing device spacing requirements.
Support:
Four types of lighting devices are commonly used in TTC zones. They
are floodlights, flashing warning beacons, warning lights, and steady-burn
electric lamps.
Option:
Lighting devices may be used to supplement retroreflectorized signs,
barriers, and channelizing devices.
During normal daytime maintenance operations, the functions of flashing warning beacons may be provided by high-intensity rotating, flashing, oscillating, or strobe lights on a maintenance vehicle.
Standard:
Although vehicle hazard warning lights are permitted to be used
to supplement high-intensity rotating, flashing, oscillating, or
strobe lights, they shall not be used instead of high-intensity
rotating, flashing, oscillating, or strobe lights.
Section 6F.76 Floodlights
Support:
Utility, maintenance, or construction activities on highways are
frequently conducted during nighttime periods when vehicular traffic
volumes are lower. Large construction projects are sometimes operated
on a double-shift basis requiring night work (see Section
6G.20).
Guidance:
When nighttime work is being performed, floodlights should be used
to illuminate the work area, equipment crossings, and other areas.
Standard:
Except in emergency situations, flagger situations shall be illuminated
at night. Floodlighting shall not produce a disabling glare condition
for approaching road users, flaggers, or workers.
Guidance:
The adequacy of the floodlight placement and elimination of potential
glare should be determined by driving through and observing the
floodlighted area from each direction on all approaching roadways
after the initial floodlight setup, at night, and periodically.
Support:
Desired illumination levels vary depending upon the nature of the
task involved. An average horizontal luminance of 50 lux (5 foot
candles) can be adequate for general activities. Tasks requiring
high levels of precision and extreme care can require an average
horizontal luminance of 216 lux (20 foot candles).
Section 6F.77 Flashing Warning Beacons
Support:
Flashing warning beacons are often used to supplement a TTC device.
Standard:
Flashing warning beacons shall comply with the provisions of Chapter
4K. A flashing warning beacon shall be a flashing yellow light
with a minimum nominal diameter of 200 mm (8 in).
Guidance:
Flashing warning beacons should be operated 24 hours per day.
Support:
The temporary terminus of a freeway is an example of a location
where flashing warning beacons alert drivers to the changing roadway
conditions and the need to reduce speed in transitioning from the
freeway to another roadway type.
Section 6F.78 Warning Lights
Support:
Type A, Type B, Type C, and Type D 360-degree warning lights are
portable, powered, yellow, lens-directed, enclosed lights.
Standard
Warning lights shall be in accordance with the current ITE "Purchase
Specification for Flashing and Steady-Burn Warning Lights"
(see Section 1A.11).
When warning lights are used, they shall be mounted on signs or channelizing devices in a manner that, if hit by an errant vehicle, they will not be likely to penetrate the windshield.
Guidance:
The maximum spacing for warning lights should be identical to the
channelizing device spacing requirements.
Support:
The light weight and portability of warning lights are advantages
that make these devices useful as supplements to the retroreflectorization
on signs and channelizing devices. The flashing lights are effective
in attracting road users' attention.
Option:
Warning lights may be used in either a steady-burn or flashing mode.
Standard:
Flashing warning lights shall not be used for delineation, as a
series of flashers fails to identify the desired vehicle path.
Type A Low-Intensity Flashing warning lights, Type C Steady-Burn warning lights, and Type D 360-degree Steady-Burn warning lights shall be maintained so as to be capable of being visible on a clear night from a distance of 900 m (3,000 ft). Type B High-Intensity Flashing warning lights shall be maintained so as to be capable of being visible on a sunny day when viewed without the sun directly on or behind the device from a distance of 300 m (1,000 ft).
Warning lights shall have a minimum mounting height of 750 mm (30 in) to the bottom of the lens.
Support:
Type A Low-Intensity Flashing warning lights are used to warn road
users during nighttime hours that they are approaching or proceeding
in a potentially hazardous area.
Option:
Type A warning lights may be mounted on channelizing devices.
Support:
Type B High-Intensity Flashing warning lights are used to warn road
users during both daylight and nighttime hours that they are approaching
a potentially hazardous area.
Option:
Type B warning lights are designed to operate 24 hours per day and
may be mounted on advance warning signs or on independent supports.
Type C Steady-Burn warning lights and Type D 360-degree Steady-Burn warning lights may be used during nighttime hours to delineate the edge of the traveled way.
Guidance:
When used to delineate a curve, Type C and Type D 360-degree warning
lights should only be used on devices on the outside of the curve,
and not on the inside of the curve.
Section 6F.79 Steady-Burn Electric Lamps
Support:
Steady-Burn electric lamps are a series of low-wattage, yellow,
electric lamps, generally hard-wired to a 110-volt external power
source.
Option:
Steady-Burn electric lamps may be used in place of Type C Steady-Burn
warning lights (see Section 6F.78).
Section 6F.80 Temporary Traffic Control Signals
Standard:
Temporary traffic control signals (see Section
4D.20) used to control road user movements through TTC zones
and in other TTC situations shall meet the applicable provisions
of Part 4.
Support:
Temporary traffic control signals are typically used in TTC zones
such as temporary haul road crossings; temporary one-way operations
along a one-lane, two-way highway; temporary one-way operations
on bridges, reversible lanes, and intersections.
Standard:
One-lane, two-way vehicular traffic flow (see Chapter
4G) requires an all-red interval of sufficient duration for
road users to clear the portion of the TTC zone controlled by the
traffic control signals. Safeguards shall be incorporated to avoid
the possibility of conflicting signal indications at each end of
the TTC zone.
Guidance:
Where pedestrian traffic is detoured to a temporary traffic control
signal, engineering judgment should be used to determine if pedestrian
signals or accessible pedestrian signals (see Section
4E.06) are needed for crossing along an alternate route.
When temporary traffic control signals are used, conflict monitors typical of traditional traffic control signal operations should be used.
Option:
Temporary traffic control signals may be portable or temporarily
mounted on fixed supports.
Standard:
The supports for temporary traffic control signals shall not encroach
into the minimum required width of a "pedestrian access route"
of 1200 mm (48 in) or an "alternate circulation path"
of 900 mm (36 in).
Guidance:
Temporary traffic control signals should only be used in situations
where temporary traffic control signals are preferable to other
means of traffic control, such as changing the work staging or work
zone size to eliminate one-way vehicular traffic movements, using
flaggers to control one-way or crossing movements, using STOP or
YIELD signs, and using warning devices alone.
Support:
Factors related to the design and application of temporary traffic
control signals include the following:
- Safety and road user needs;
- Work staging and operations;
- The feasibility of using other TTC strategies (for example, flaggers, providing space for two lanes, or detouring road users, including bicyclists and pedestrians);
- Sight distance restrictions;
- Human factors considerations (for example, lack of driver familiarity with temporary traffic control signals);
- Road-user volumes including roadway and intersection capacity;
- Affected side streets and driveways;
- Vehicle speeds;
- The placement of other TTC devices;
- Parking;
- Turning restrictions;
- Pedestrians;
- The nature of adjacent land uses (such as residential or commercial);
- Legal authority;
- Signal phasing and timing requirements;
- Full-time or part-time operation;
- Actuated, fixed-time, or manual operation;
- Power failures or other emergencies;
- Inspection and maintenance needs;
- Need for detailed placement, timing, and operation records; and
- Operation by contractors or by others.
Although temporary traffic control signals can be mounted on trailers or lightweight portable supports, fixed supports offer superior resistance to displacement or damage by severe weather, vehicle impact, and vandalism.
Guidance:
Other TTC devices should be used to supplement temporary traffic
control signals, including warning and regulatory signs, pavement
markings, and channelizing devices.
The design and placement of temporary traffic control signals should include interconnection to other traffic control signals along the subject roadway.
Temporary traffic control signals not in use should be covered or removed.
Section 6F.81 Temporary Traffic Barriers
Support:
Temporary traffic barriers are devices designed to help prevent
penetration by vehicles while minimizing injuries to vehicle occupants,
and are designed to protect workers, bicyclists, and pedestrians.
The four primary functions of temporary traffic barriers are:
- To keep vehicular traffic from entering work areas, such as excavations or material storage sites;
- To separate workers, bicyclists, and pedestrians from motor vehicle traffic;
- To separate opposing directions of vehicular traffic; and
- To separate vehicular traffic, bicyclists, and pedestrians from the work area such as false work for bridges and other exposed objects.
Option:
Temporary traffic barriers, including shifting portable or movable
barrier installations to accommodate varying directional vehicular
traffic demands, may be used to separate two-way vehicular traffic.
Guidance:
Because the protective requirements of a TTC situation have priority
in determining the need for temporary traffic barriers, their use
should be based on an engineering study. When serving the additional
function of channelizing vehicular traffic (see Section
6F.65), temporary traffic barriers should be a light color for
increased visibility.
Standard:
Temporary traffic barriers shall be supplemented with standard delineation,
pavement markings, or channelizing devices for improved daytime
and nighttime visibility if they are used to channelize vehicular
traffic. The delineation color shall match the applicable pavement
marking color.
In order to mitigate the effect of striking the end of a temporary traffic barrier, the end shall be installed in accordance with AASHTO's "Roadside Design Guide" (see Section 1A.11) by flaring until the end is outside the acceptable clear zone or by providing crashworthy end treatments.
Option:
Warning lights or steady-burn electric lamps may be mounted on temporary
traffic barrier installations.
Support:
A movable barrier is a linear system of connected barrier segments
that can rapidly be shifted laterally by using a specially designed
transfer vehicle. The transfer is accomplished in a manner that
does not interfere with vehicular traffic in adjacent lanes. Applications
of movable barriers include the following:
- Closing an additional lane during work periods while maintaining the advantage of having the travel way separated from the work space by a barrier;
- Closing an additional lane during off-peak periods to provide extra space for work activities without adversely impacting vehicular traffic flow; and
- Creating a temporary reversible lane, thus providing unbalanced capacity favoring the major direction of vehicular traffic flow.
More specific information on the use of temporary traffic barriers is contained in Chapters 8 and 9 of AASHTO's "Roadside Design Guide" (see Section 1A.11).
Section 6F.82 Crash Cushions
Support:
Crash cushions are systems that mitigate the effects of errant vehicles
that strike obstacles, either by smoothly decelerating the vehicle
to a stop when hit head-on, or by redirecting the errant vehicle.
The two types of crash cushions that are used in TTC zones are stationary
crash cushions and truck-mounted attenuators. Crash cushions in
TTC zones help protect the drivers from the exposed ends of barriers,
fixed objects, shadow vehicles, and other obstacles. Specific information
on the use of crash cushions can be found in AASHTO's "Roadside
Design Guide" (see Section 1A.11).
Standard:
Crash cushions shall be crashworthy. They shall also be designed
for each application to stop or redirect errant vehicles under prescribed
conditions. Crash cushions shall be periodically inspected to verify
that they have not been hit or damaged. Damaged crash cushions shall
be promptly repaired or replaced to maintain their crashworthiness.
Support:
Stationary crash cushions are used in the same manner as permanent
highway installations to protect drivers from the exposed ends of
barriers, fixed objects, and other obstacles.
Standard:
Stationary crash cushions shall be designed for the specific application
intended.
Truck-mounted attenuators shall be energy-absorbing devices attached to the rear of shadow trailers or trucks. If used, the shadow vehicle with the attenuator shall be located in advance of the work area, workers, or equipment to reduce the severity of rear-end crashes from errant vehicles.
Support:
Trucks or trailers are often used as shadow vehicles to protect
workers or work equipment from errant vehicles. These shadow vehicles
are normally equipped with flashing arrows, changeable message signs,
and/or high-intensity rotating, flashing, oscillating, or strobe
lights located properly in advance of the workers and/or equipment
that they are protecting. However, these shadow vehicles might themselves
cause injuries to occupants of the errant vehicles if they are not
equipped with truckmounted attenuators.
Guidance:
The shadow truck should be positioned a sufficient distance in advance
of the workers or equipment being protected so that there will be
sufficient distance, but not so much so that errant vehicles will
travel around the shadow truck and strike the protected workers
and/or equipment.
Support:
Chapter 9 of AASHTO's "Roadside Design Guide" (see Section
1A.11) contains additional information regarding the use of shadow
vehicles.
Guidance:
If used, the truck-mounted attenuator should be used in accordance
with the manufacturer's specifications.
Section 6F.83 Vehicle-Arresting Systems
Support:
Vehicle-arresting systems are designed to prevent penetration into
activity areas while providing for smooth, reasonably safe deceleration
for the errant vehicles. They can consist of portable netting, cables,
and energy-absorbing anchors.
Guidance:
When used, a vehicle-arresting system should be used in accordance
with the manufacturer's specifications, and should be located so
that vehicles are not likely to penetrate the location that the
system is designed to protect.
Section 6F.84 Rumble Strips
Support:
Transverse rumble strips consist of intermittent narrow, transverse
areas of rough-textured or slightly raised or depressed road surface
that extend across the travel lanes to alert drivers to unusual
vehicular traffic conditions. Through noise and vibration they attract
the driver's attention to such features as unexpected changes in
alignment and to conditions requiring a stop.
Longitudinal rumble strips consist of a series of rough-textured or slightly raised or depressed road surfaces located along the shoulder to alert road users that they are leaving the travel lanes.
Standard:
If it is desirable to use a color other than the color of the pavement
for a longitudinal rumble strip, the color of the rumble strip shall
be the same color as the longitudinal line the rumble strip supplements.
If the color of a transverse rumble strip used within a travel lane is not the color of the pavement, the color of the rumble strip shall be white.
Option:
Intervals between transverse rumble strips may be reduced as the
distance to the approached conditions is diminished in order to
convey an impression that a closure speed is too fast and/or that
an action is imminent. A sign warning drivers of the onset of rumble
strips may be placed in advance of any transverse rumble strip installation.
Guidance:
Transverse rumble strips should be placed transverse to vehicular
traffic movement. They should not adversely affect overall pavement
skid resistance under wet or dry conditions.
In urban areas, even though a closer spacing might be warranted, transverse rumble strips should be designed in a manner that does not promote unnecessary braking or erratic steering maneuvers by road users.
Transverse rumble strips should not be placed on sharp horizontal or vertical curves.
Rumble strips should not be placed through pedestrian crossings or on bicycle routes.
Transverse rumble strips should not be placed on roadways used by bicyclists unless a minimum clear path of 1.2 m (4 ft) is provided at each edge of the roadway or on each paved shoulder as described in AASHTO's "Guide to the Development of Bicycle Facilities" (see Section 1A.11).
Longitudinal rumble strips should not be placed on the shoulder of a roadway that is used by bicyclists unless a minimum clear path of 1.2 m (4 ft) is also provided on the shoulder.
Section 6F.85 Screens
Support:
Screens are used to block the road users' view of activities that
can be distracting. Screens might improve safety and motor vehicle
traffic flow where volumes approach the roadway capacity because
they discourage gawking and reduce headlight glare from oncoming
motor vehicle traffic.
Guidance:
Screens should not be mounted where they could adversely restrict
road user visibility and sight distance and adversely affect the
reasonably safe operation of vehicles.
Option:
Screens may be mounted on the top of temporary traffic barriers
that separate two-way motor vehicle traffic.
Guidance:
Design of screens should be in accordance with Chapter 9 of AASHTO's
"Roadside Design Guide" (see Section 1A.11).
Section 6F.86 Future and Experimental Devices
Support:
The States, FHWA, AASHTO, the Transportation Research Board, and
other organizations conduct research and experimentation on new
traffic control and safety devices. Users of this Manual are encouraged
to stay abreast of these current efforts and to use such devices
with care so as to avoid presenting road users with unusual or confusing
situations that might be abnormal or unexpected.
Standard:
New traffic control devices shall conform to the provisions for
design, use, and application set forth in this Manual. New traffic
control devices that do not conform with the provisions in this
Manual shall be subject to experimentation, documentation, and adoption
following the provisions of Section
1A.10.
