Chapter 6F. Temporary Traffic Control Zone Devices
Section 6F.17 ROAD (STREET) WORK Sign (W20-1)
Guidance:
The ROAD (STREET) WORK (W20-1) sign (see Figure
6F-4, Sheet 3 of 4), which serves as a general warning of obstructions
or restrictions, should be located in advance of the work space
or any detour, on the road where the work is taking place.
Where traffic can enter a TTC zone from a crossroad or a major (high-volume) driveway, an advance warning sign should be used on the crossroad or major driveway.
Standard:
The ROAD (STREET) WORK (W20-1) sign shall have the legend ROAD (STREET)
WORK, XX m (FT), XX km (MILES), or AHEAD.
Section 6F.18 DETOUR Sign (W20-2)
Guidance:
The DETOUR (W20-2) sign (see Figure 6F-4, Sheet 3 of 4) should be
used in advance of a road user detour over a different roadway or
route.
Standard: The DETOUR sign shall have the legend DETOUR, XX m (FT), XX km (MILES), or AHEAD.
Section 6F.19 ROAD (STREET) CLOSED Sign (W20-3)
Guidance: The ROAD (STREET) CLOSED (W20-3) sign (see Figure 6F-4, Sheet 3 of 4) should be used in advance of the point where a highway is closed to all road users, or to all but local road users.
Standard: The ROAD (STREET) CLOSED sign shall have the legend ROAD (STREET) CLOSED, XX m (FT), XX km (MILES), or AHEAD.
Section 6F.20 ONE LANE ROAD Sign (W20-4)
Standard:
The ONE LANE ROAD (W20-4) sign (see Figure 6F-4, Sheet 3 of 4) shall
be used only in advance of that point where motor vehicle traffic
in both directions must use a common single lane (see Section
6C.10). It shall have the legend ONE LANE ROAD, XX m (FT), XX
km (MILES), or AHEAD.
Section 6F.21 Lane(s) Closed Signs (W20-5, W20-5a)
Standard:
The Lane(s) Closed sign (see Figure 6F-4, Sheet 3 of 4) shall be
used in advance of that point where one or more through lanes of
a multi-lane roadway are closed.
For a single lane closure, the Lane Closed (W20-5) sign (see Figure 6F-4, Sheet 3 of 4) shall have the legend RIGHT (LEFT) LANE CLOSED, XX m (FT), XX km (MILES), or AHEAD. Where two adjacent lanes are closed, the W20-5a sign (see Figure 6F-4, Sheet 3 of 4) shall have the legend RIGHT (LEFT) TWO LANES CLOSED, XX m (FT), XX km (MILES), or AHEAD.
Section 6F.22 CENTER LANE CLOSED AHEAD Signs (W9-3, W9-3a)
Guidance:
The CENTER LANE CLOSED AHEAD (W9-3) sign (see Figure
6F-4, Sheet 2 of 4) should be used in advance of that point
where work occupies the center lane(s) and approaching motor vehicle
traffic is directed to the right or left of the work zone in the
center lane.
The Center Lane Closed Ahead (W9-3a) symbol sign (see Figure 6H-38) may be substituted for the CENTER LANE CLOSED AHEAD (W9-3) word message sign.
Section 6F.23 THRU TRAFFIC MERGE LEFT (RIGHT) Sign (W4-7)
Guidance:
The THRU TRAFFIC MERGE LEFT (RIGHT) (W4-7) sign (see Figure
6F-4, Sheet 1 of 4) should be used in advance of an intersection
where one or more lane closures on the far side of a multi-lane
intersection require through vehicular traffic on the approach to
the intersection to use the left (right) lane to proceed through
the intersection.
Section 6F.24 Lane Ends Sign (W4-2)
Option:
The Lane Ends (W4-2) symbol sign (see Figure 6F-4, Sheet 1 of 4)
may be used to warn drivers of the reduction in the number of lanes
for moving motor vehicle traffic in the direction of travel on a
multi-lane roadway.
Section 6F.25 ON RAMP Plaque (W13-4)
Guidance:
When work is being done on a ramp, but the ramp remains open, the
ON RAMP (W13-4) plaque (see Figure
6F-4, Sheet 3 of 4) should be used to supplement the advance
ROAD WORK sign.
Section 6F.26 RAMP NARROWS Sign (W5-4)
Guidance:
The RAMP NARROWS (W5-4) sign (see Figure
6F-4, Sheet 1 of 4) should be used in advance of the point where
work on a ramp reduces the normal width of the ramp along a part
or all of the ramp.
Section 6F.27 SLOW TRAFFIC AHEAD Sign (W23-1)
Option:
The SLOW TRAFFIC AHEAD (W23-1) sign (see Figure
6F-4, Sheet 4 of 4) may be used on a shadow vehicle, usually
mounted on the rear of the most upstream shadow vehicle, along with
other appropriate signs for mobile operations to warn of slow moving
work vehicles. A ROAD WORK (W20-1) sign may also be used with the
SLOW TRAFFIC AHEAD sign.
Section 6F.28 EXIT OPEN, EXIT CLOSED, EXIT ONLY Signs (E5-2, E5-2a, E5-3)
Option:
An EXIT OPEN (E5-2), EXIT CLOSED (E5-2a), or EXIT ONLY (E5-3) sign
(see Figure 6F-5) may be used
to supplement other warning signs where work is being conducted
in the vicinity of an exit ramp and where the exit maneuver for
motor vehicle traffic using the ramp is different from the normal
condition.
Guidance:
When an exit ramp is closed, an EXIT CLOSED panel with a black legend
and border on an orange background should be placed diagonally across
the interchange/intersection guide signs.
Section 6F.29 Flagger Sign (W20-7a, W20-7)
Guidance:
The Flagger (W20-7a) symbol sign (see Figure
6F-4, Sheet 3 of 4) should be used in advance of any point where
a flagger is stationed to control road users.
Option:
A distance legend may be displayed on a supplemental plaque below
the Flagger sign. The sign may be used with appropriate legends
or in conjunction with other warning signs, such as the BE PREPARED
TO STOP (W3-4) sign (see Figure
6F-4, Sheet 1 of 4).
The FLAGGER (W20-7) word message sign with distance legends may be substituted for the Flagger (W20-7a) symbol sign.
Standard:
The Flagger sign shall be removed, covered, or turned away from
road users when the flagging operations are not occurring.
Section 6F.30 Two-Way Traffic Sign (W6-3)
Guidance:
When one roadway of a normally divided highway is closed, with two-way
vehicular traffic maintained on the other roadway, the Two-Way Traffic
(W6-3) sign (see Figure 6F-4,
Sheet 2 of 4) should be used at the beginning of the two-way
vehicular traffic section and at intervals to remind road users
of opposing vehicular traffic.
Section 6F.31 Workers Sign (W21-1, W21-1a)
Option:
A Workers (W21-1a) symbol sign (see
Figure 6F-4, Sheet 3 of 4) may be used to alert road users of
workers in or near the roadway.
Guidance:
In the absence of other warning devices, a Workers symbol sign should
be used when workers are in the roadway.
Option:
The WORKERS (W21-1) word message sign may be used as an alternate
to the Workers (W21-1a) symbol sign.
Section 6F.32 FRESH OIL (TAR) Sign (W21-2)
Guidance:
The FRESH OIL (TAR) (W21-2) sign (see Figure 6F-4, Sheet 3 of 4)
should be used to warn road users of the surface treatment.
Section 6F.33 ROAD MACHINERY AHEAD Sign (W21-3)
Option:
The ROAD MACHINERY AHEAD (W21-3) sign (see Figure 6F-4, Sheet 3
of 4) may be used to warn of machinery operating in or adjacent
to the roadway.
Section 6F.34 Motorized Traffic Signs (W8-6, W11-10)
Option:
Motorized Traffic (W8-6, W11-10) signs may be used to alert road
users to locations where unexpected travel on the roadway or entries
into or departures from the roadway by construction vehicles might
occur. The TRUCK CROSSING (W8-6) word message sign may be used as
an alternate to the Truck Crossing symbol (W11-10) sign (See Figure
6F-4, Sheet 2 of 4) where there is an established construction
vehicle crossing of the roadway.
Support:
These locations might be relatively confined or might occur randomly
over a segment of roadway.
Section 6F.35 Shoulder Work Signs (W21-5, W21-5a, W21-5b)
Support:
Shoulder Work signs (see Figure 6F-4, Sheets 3 and 4 of 4) warn
of maintenance, reconstruction, or utility operations on the highway
shoulder where the roadway is unobstructed.
Standard:
The Shoulder Work sign shall have the legend SHOULDER WORK (W21-5),
RIGHT (LEFT) SHOULDER CLOSED (W21-5a), or RIGHT (LEFT) SHOULDER
CLOSED XXX m (FT) or AHEAD (W21-5b).
Option:
The Shoulder Work sign may be used in advance of the point on a
nonlimited access highway where there is shoulder work. It may be
used singly or in combination with a ROAD WORK NEXT X km (MILES)
or ROAD WORK AHEAD sign.
Guidance:
On freeways and expressways, the RIGHT (LEFT) SHOULDER CLOSED XXX
m (FT) or AHEAD (W21-5b) sign followed by RIGHT (LEFT) SHOULDER
CLOSED (W21-5a) sign should be used in advance of the point where
the shoulder work occurs and should be preceded by a ROAD WORK AHEAD
sign.
Section 6F.36 SURVEY CREW Sign (W21-6)
Guidance:
The SURVEY CREW (W21-6) sign (see Figure
6F-4, Sheet 4 of 4) should be used to warn of surveying crews
working in or adjacent to the roadway.
Section 6F.37 UTILITY WORK Sign (W21-7)
Option:
The UTILITY WORK (W21-7) sign (see Figure 6F-4, Sheet 4 of 4) may
be used as an alternate to the ROAD (STREET) WORK (W20-1) sign for
utility operations on or adjacent to a highway.
Support:
Typical examples of where the UTILITY WORK sign is used appear in
Figures 6H-4,
6H-6, 6H-10,
6H-15,
6H-18,
6H-21,
6H-22,
6H-26,
and 6H-33.
Standard:
The UTILITY WORK sign shall carry the legend UTILITY WORK, XX m
(FT), XX km (MILES), or AHEAD.
Section 6F.38 Signs for Blasting Areas
Support:
Radio-Frequency (RF) energy can cause the premature firing of electric
detonators (blasting caps) used in TTC zones.
Standard:
Road users shall be warned to turn off mobile radio transmitters
and cellular telephones where blasting operations occur. A sequence
of signs shall be prominently displayed to direct operators of mobile
radio equipment, including cellular telephones, to turn off transmitters
in a blasting area. These signs shall be covered or removed when
there are no explosives in the area or the area is otherwise secured.
Section 6F.39 BLASTING ZONE AHEAD Sign (W22-1)
Standard:
The BLASTING ZONE AHEAD (W22-1) sign (see Figure
6F-4, Sheet 4 of 4) shall be used in advance of any TTC zone
where explosives are being used. The TURN OFF 2-WAY RADIO AND CELL
PHONE and END BLASTING ZONE signs shall be used in sequence with
this sign.
Section 6F.40 TURN OFF 2-WAY RADIO AND CELL PHONE Sign (W22-2)
Standard:
The TURN OFF 2-WAY RADIO AND CELL PHONE (W22-2) sign (see Figure
6F-4, Sheet 4 of 4) shall follow the BLASTING ZONE AHEAD sign and
shall be placed at least 300 m (1,000 ft) before the beginning of
the blasting zone.
Section 6F.41 END BLASTING ZONE Sign (W22-3)
Standard:
The END BLASTING ZONE (W22-3) sign (see Figure 6F-4, Sheet 4 of
4) shall be placed a minimum of 300 m (1,000 ft) past the blasting
zone.
Option:
The END BLASTING ZONE sign may be placed either with or preceding
the END ROAD WORK sign.
Section 6F.42 Shoulder Signs (W8-4, W8-9, W8-9a)
Option:
The SOFT SHOULDER (W8-4) sign (see Figure
6F-4, Sheet 2 of 4) may be used to warn of a soft shoulder condition.
The LOW SHOULDER (W8-9) sign (see Figure 6F-4, Sheet 2 of 4) may be used to warn of a shoulder condition where there is an elevation difference of less than 75 mm (3 in) between the shoulder and the travel lane.
Guidance:
The SHOULDER DROP OFF (W8-9a) sign (see Figure 6F-4, Sheet 2 of
4) should be used when an unprotected shoulder drop-off, adjacent
to the travel lane, exceeds 75 mm (3 in) in depth for a significant
continuous lenth along the roadway, based on engineering judgment.
Section 6F.43 UNEVEN LANES Sign (WB-11)
Guidance:
The UNEVEN LANES (W8-11) sign (see Figure 6F-4, Sheet 2 of 4) should
be used during operations that create a difference in elevation
between adjacent lanes that are open to travel.
Section 6F.44 NO CENTER STRIPE Sign (W8-12)
Guidance:
The NO CENTER STRIPE (W8-12) sign (see Figure 6F-4, Sheet 2 of 4)
should be used when the work obliterates the centerline pavement
markings. This sign should be placed at the beginning of the TTC
zone and repeated at 3.2 km (2 mi) intervals in long TTC zones.
Section 6F.45 Double Reverse Curve Signs (W24 Series)
Option:
The Double Reverse Curve (W24-1, W24-1a, or W24-1b) sign (see Figure
6F-4, Sheet 4 of 4) may be used when the tangent distance between
two reverse curves is less than 180m (600 ft), thus making it difficult
for a second Reverse Curve (W1-4 Series) sign to be placed between
the curves.
Standard:
If a Double Reverse Curve sign is used, the number of lanes illustrated
on the sign shall be the same as the number of through lanes available
to road users, and the direction of the double reverse curve shall
be appropriately illustrated.
Section 6F.46 Other Warning Signs
Option:
Advance warning signs may be used by themselves or with other advance
warning signs.
Besides the warning signs specifically related to TTC zones, several other warning signs in Part 2 may apply in TTC zones.
Standard:
Except as noted in Section 6F.02,
other warning signs that are used in TTC zones shall have black
legends and borders on an orange background.
Section 6F.47 Special Warning Signs
Option:
Special warning signs may be used based on engineering judgment.
Guidance:
Special warning signs should conform to the general requirements
of color, shape, and alphabet size and series. The sign message
should be brief, legible, and clear.
Section 6F.48 Advisory Speed Plaque (W13-1)
Option:
In combination with a warning sign, an Advisory Speed (W13-1) plaque
(see Figure 6F-4, Sheet 2 of 4)
may be used to indicate a recommended safe speed through the TTC
zone.
Standard:
The Advisory Speed plaque shall not be used in conjunction with
any sign other than a warning sign, nor shall it be used alone.
When used with orange TTC zone signs, this plaque shall have a black
legend and border on an orange background. The sign shall be at
least 600 x 600 mm (24 x 24 in) in size when used with a sign that
is 900 x 900 mm (36 x 36 in) or larger. Except in emergencies, an
Advisory Speed plaque shall not be mounted until the recommended
speed is determined by the highway agency.
Section 6F.49 Supplementary Distance Plaque (W7-3a)
Option:
In combination with a warning sign, a Supplementary Distance (W7-3a)
plaque with the legend NEXT XX km (MILES) may be used to indicate
the length of highway over which a work activity is being conducted,
or over which a condition exists in the TTC zone.
In long TTC zones, Supplementary Distance plaques with the legend NEXT XX km (MILES) may be placed in combination with warning signs at regular intervals within the zone to indicate the remaining length of highway over which the TTC work activity or condition exists.
Standard:
The Supplementary Distance plaque with the legend NEXT XX km (MILES)
shall not be used in conjunction with any sign other than a warning
sign, nor shall it be used alone. When used with orange TTC zone
signs, this plaque shall have a black legend and border on an orange
background. The sign shall be at least 750 x 600 mm (30 x 24 in)
in size when used with a sign that is 900 x 900 mm (36 x 36 in)
or larger.
Guidance:
When used in TTC zones, the Supplementary Distance plaque with the
legend NEXT XX km (MILES) should be placed below the initial warning
sign designating that, within the approaching zone, a temporary
work activity or condition exists.
Section 6F.50 Guide Signs
Support:
Guide signs along highways provide road users with information to
help them along their way through the TTC zone. The design of guide
signs is presented in Part 2.
Guidance:
The following guide signs should be used in TTC zones as needed:
- Standard route markings, where temporary route changes are necessary;
- Directional signs and street name signs; and
- Special guide signs relating to the condition or work being done.
Standard:
If additional temporary guide signs are used in TTC zones, they
shall have a black legend and border on an orange background.
Option:
Guide signs used in TTC incident management situations may have
a black legend and border on a fluorescent pink background.
When directional signs and street name signs are used in conjunction with detour routing, these signs may have a black legend and border on an orange background.
When permanent directional signs or permanent street name signs are used in conjunction with detour signing, they may have a white legend on a green background.
Section 6F.51 ROAD WORK NEXT XX km (MILES) Sign (G20-1)
Guidance:
The ROAD WORK NEXT XX km (MILES) (G20-1) sign (see Figure
6F-4, Sheet 4 of 4) should be installed in advance of TTC zones
that are more than 3.2 km (2 mi) in length.
Option:
The ROAD WORK NEXT XX km (MILES) sign may be mounted on a Type III
barricade. The sign may also be used for TTC zones of shorter length.
Standard:
The distance shown on the ROAD WORK NEXT XX km (MILES) sign shall
be stated to the nearest whole kilometer (or mile).
Section 6F.52 END ROAD WORK Sign (G20-2)
Guidance:
When used, the END ROAD WORK (G20-2) sign (see Figure 6F-4, Sheet
4 of 4) should be placed near the end of the termination area, as
determined by engineering judgment.
Option:
The END ROAD WORK sign may be installed on the back of a warning
sign facing the opposite direction of road users or on the back
of a Type III barricade.
Section 6F.53 Detour Signs (M4-8, M4-8a, M4-8b, M4-9, M4-9a, M4-9b, M4-9c, and M4-10)
Standard:
Each detour shall be adequately marked with standard temporary route
signs and destination signs.
Option:
Detour signs in TTC incident management situations may have a black
legend and border on a fluorescent pink background.
The Detour Arrow (M4-10) sign (see Figure 6F-5) may be used where a detour route has been established.
The DETOUR (M4-8) sign (see Figure 6F-5) may be mounted at the top of a route sign assembly to mark a temporary route that detours from a highway, bypasses a section closed by a TTC zone, and rejoins the highway beyond the TTC zone.
Guidance:
The Detour Arrow (M4-10) sign should normally be mounted just below
the ROAD CLOSED (R11-2, R11-3a, or R11-4) sign. The Detour Arrow
sign should include a horizontal arrow pointed to the right or left
as required.
The DETOUR (M4-9) sign (see Figure 6F-5) should be used for unnumbered highways, for emergency situations, for periods of short durations, or where, over relatively short distances, road users are guided along the detour and back to the desired highway without route signs.
A Street Name sign should be placed above, or the street name should be incorporated into, a DETOUR (M4-9) sign to indicate the name of the street being detoured.
Option:
The END DETOUR (M4-8a) or END (M4-8b) sign (see Figure 6F-5) may
be used to indicate that the detour has ended.
Guidance:
When the END DETOUR sign is used on a numbered highway, the sign
should be mounted above a sign after the end of the detour.
The Pedestrian/Bicycle Detour (M4-9a) sign (see Figure 6F-5) should be used where a pedestrian/bicycle detour route has been established because of the closing of a pedestrian/bicycle facility to through traffic.
Standard:
If used, the Pedestrian/Bicycle Detour sign shall have an arrow
pointing in the appropriate direction.
Option:
The arrow on a Pedestrian/Bicycle Detour sign may be on the sign
face or on a supplemental plaque.
The Pedestrian Detour (M4-9b) sign or Bicycle Detour (M4-9c) sign (see Figure 6F-5) may be used where a pedestrian or bicycle detour route (not both) has been established because of the closing of the pedestrian or bicycle facility to through traffic.
Section 6F.54 PILOT CAR FOLLOW ME Sign (G20-4)
Standard:
The PILOT CAR FOLLOW ME (G20-4) sign (see Figure
6F-4, Sheet 4 of 4) shall be mounted in a conspicuous position
on the rear of a vehicle used for guiding one-way vehicular traffic
through or around a TTC zone. A flagger shall be stationed on the
approach to the activity area to stop vehicular traffic until the
pilot vehicle is available.
Section 6F.55 Portable Changeable Message Signs
Standard:
Portable Changeable Message signs shall be TTC devices with the
flexibility to display a variety of messages. Each message shall
consist of either one or two phases. A phase shall consist of up
to three lines of eight characters per line. Each character module
shall use at least a five wide and seven high pixel matrix.
Support:
Portable Changeable Message signs are used most frequently on high-density
urban freeways, but have applications on all types of highways where
highway alignment, road user routing problems, or other pertinent
conditions require advance warning and information.
Portable Changeable Message signs have a wide variety of applications in TTC zones including: roadway, lane, or ramp closures, crash or emergency incident management, width restriction information, speed control or reductions, advisories on work scheduling, road user management and diversion, warning of adverse conditions or special events, and other operational control.
The primary purpose of Portable Changeable Message signs in TTC zones is to advise the road user of unexpected situations. Some typical applications include the following:
- Where the speed of vehicular traffic is expected to drop substantially;
- Where significant queuing and delays are expected;
- Where adverse environmental conditions are present;
- Where there are changes in alignment or surface conditions;
- Where advance notice of ramp, lane, or roadway closures is needed;
- Where crash or incident management is needed; and/or
- Where changes in the road user pattern occur.
Guidance:
The components of a Portable Changeable Message sign should include:
a message sign panel, control systems, a power source, and mounting
and transporting equipment.
Portable Changeable Message signs should subscribe to the principles established in Section 2A.07 and other sections of this Manual and, to the extent practical, with the design (that is, color, letter size and shape, and borders) and applications prescribed in this Manual, except that the reverse colors for the letters and the background are considered acceptable.
The front face of the sign should be covered with a protective material. The color of the elements should be yellow or orange on a black background.
Portable Changeable Message signs should be visible from 800 m (0.5 mi) under both day and night conditions. For a trailer or large truck mounted sign, the letter height should be a minimum of 450 mm (18 in). For Changeable Message signs mounted on service patrol trucks, the letter height should be a minimum of 250 mm (10 in).
The message panel should have adjustable display rates (minimum of 3 seconds per phase), so that the entire message can be read at least twice at the posted speed, the off-peak 85th-percentile speed prior to work starting, or the anticipated operating speed.
Messages should be designed taking into account the following factors:
- Each phase should convey a single thought.
- If the message can be displayed in one phase, the top line should present the problem, the center line should present the location or distance ahead, and the bottom line should present the recommended driver action.
- The message should be as brief as possible.
- When a message is longer than two phases, additional Portable Changeable Message signs should be used.
- When abbreviations are used, they should be easily understood (see Section 1A.14).
Option:
The message sign panel may vary in size.
Smaller letter sizes may be used on a Portable Changeable Message sign mounted on a trailer or large truck provided that the message is legible from at least 200 m (650 ft), or mounted on a service patrol truck provided that the message is legible from at least 100 m (330 ft).
Two Portable Changeble Message signs may be used for the purpose of allowing the entire message to be read twice at the posted speed.
Standard:
Portable Changeable Message signs shall automatically adjust their
brightness under varying light conditions, to maintain legibility.
The control system shall include a display screen upon which messages can be reviewed before being displayed on the message sign. The control system shall be capable of maintaining memory when power is unavailable.
Portable Changeable Message signs shall be equipped with a power source and a battery back-up to provide continuous operation when failure of the primary power source occurs.
The mounting of Portable Changeable Message signs on a trailer, a large truck, or a service patrol truck shall be such that the bottom of the message sign panel shall be a minimum of 2.1 m (7 ft) above the roadway in urban areas and 1.5 m (5 ft) above the roadway in rural areas when it is in the operating mode.
The text of the messages shall not scroll or travel horizontally or vertically across the face of the sign.
Guidance:
Portable Changeable Message signs should be used as a supplement
to and not as a substitute for conventional signs and pavement markings.
When Portable Changeable Message signs are used for route diversion, they should be placed far enough in advance of the diversion to allow road users ample opportunity to perform necessary lane changes, to adjust their speed, or to exit the affected highway.
The Portable Changeable Message signs should be sited and aligned to provide maximum legibility. Multiple Portable Changeable Message signs should be placed on the same side of the roadway, separated from each other at distances based on Table 6C-1.
Portable Changeable Message signs should be placed on the shoulder of the roadway or, if practical, further from the traveled lane. They should be delineated with retroreflective TTC devices. When Portable Changeable Message signs are not being used, they should be removed; if not removed, they should be shielded; or if the previous two options are not feasible, they should be delineated with retroreflective TTC devices.
Portable Changeable Message sign trailers should be delineated on a permanent basis by affixing retroreflective material, known as conspicuity material, in a continuous line on the face of the trailer as seen by oncoming road users.
