Traffic congestion ahead
Traffic congestion ahead - W355
Road Signs - W355
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Traffic congestion ahead
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Safety Sign Code:
- W355
Product Description
Traffic Congestion Ahead – W355 Road Sign
The W355 Traffic Congestion Ahead road sign is a South African warning sign used to alert drivers and other road users to the possibility of slow-moving or stationary traffic ahead.
The official South African road traffic sign designation is W355 CONGESTION. The warning is intended for situations where traffic congestion may become a hazard because of traffic density or limited visibility caused by road alignment, and where drivers may need to significantly reduce speed or stop.
W355 is particularly relevant on normally free-flowing, higher-speed roads where congestion can develop unexpectedly and create a queue that approaching drivers may not see in sufficient time.
What Does the W355 Road Sign Mean?
W355 means Congestion. It warns drivers that slow-moving or stationary traffic may be present on the roadway ahead.
The sign is intended to give approaching drivers advance warning of a traffic queue or unstable traffic flow so that they can reduce speed and prepare for the possibility of coming to a stop.
W355 is a warning sign. It does not itself impose a particular speed limit or require drivers to stop at the sign.
Why Is the W355 Traffic Congestion Sign Important?
Traffic queues can develop quickly, especially on high-speed roads.
A driver travelling at normal operating speed may encounter a stationary or very slow-moving queue around a bend, over a crest or further ahead because of traffic density.
W355 provides advance warning of this possibility so drivers can begin reducing speed before reaching the back of the queue.
This is particularly important where the queue cannot be seen clearly from a long distance.
When Is W355 Used?
The SARTSM states that W355 is used to warn drivers of the possibility of slow-moving or stationary traffic in the roadway ahead where it may constitute a hazard and may require the driver to significantly reduce speed or stop.
W355 should be displayed in advance of sections where congestion occurs in an unpredictable or random manner.
This distinction is important because not every busy road or normal peak-period traffic queue automatically requires W355.
W355 and Unpredictable Traffic Congestion
The official guidance focuses on congestion that develops in an unpredictable or random way.
Where traffic flow can suddenly become unstable and speeds can fall significantly, approaching drivers may not have enough time to respond if there is no advance warning.
W355 is intended for these types of situations rather than being a general sign for every road that experiences traffic during busy periods.
W355 and Freeways
The SARTSM recommends W355 particularly for normally high-speed arterials and freeways where congestion can become unstable enough to cause significant reductions in speed or bring traffic to a stop.
These roads can present a greater difference between normal operating speed and the speed of a developing traffic queue.
An approaching driver may therefore require additional warning to reduce speed progressively.
W355 and High-Speed Arterial Roads
High-speed arterial roads can also experience sudden congestion caused by traffic demand, incidents, road restrictions and other changing conditions.
Where congestion occurs unpredictably and presents a meaningful hazard to approaching traffic, W355 may be appropriate.
W355 and Stationary Traffic
W355 includes situations where traffic may be stationary.
A stationary queue can present a serious hazard when approaching traffic is travelling much faster and has limited sight distance to the back of the queue.
The purpose of the warning is to give drivers additional time to slow down before encountering stopped vehicles.
W355 and Slow-Moving Traffic
Traffic does not have to be completely stopped for W355 to be relevant.
The sign also warns about slow-moving traffic where the reduction in speed is significant enough to create a hazard or require drivers to make a substantial speed adjustment.
W355 and Limited Visibility
The SARTSM identifies limited visibility due to road alignment or traffic density as factors that can contribute to the congestion hazard.
For example, a queue may be hidden around a bend or beyond a crest, giving approaching drivers less time to react.
W355 and Road Curves
A traffic queue around a curve may not be visible to approaching drivers until they are relatively close to the stationary vehicles.
W355 can provide advance information before the curve or affected section where the congestion hazard is likely to occur.
W355 and Road Crests
A crest can hide slow-moving or stationary traffic from approaching drivers.
Where congestion regularly develops beyond a crest in an unpredictable manner and creates a relevant hazard, advance congestion warning may be considered.
How Should Drivers Respond to W355?
Drivers approaching a W355 sign should expect slow-moving or stationary traffic ahead and adjust their driving accordingly.
Drivers should:
- Reduce speed progressively.
- Look ahead for the back of the traffic queue.
- Maintain a suitable following distance.
- Be prepared to stop.
- Watch for sudden braking by vehicles ahead.
- Remain alert for lane changes by other drivers.
- Follow variable-message signs and other traffic controls.
- Avoid sudden manoeuvres.
The correct response depends on the actual traffic speed, queue length, road conditions and visibility.
Does W355 Set a Speed Limit?
No. W355 is a warning sign and does not itself establish a legal speed limit.
Its purpose is to warn drivers that congestion may require a significant reduction in speed or may result in traffic coming to a stop.
Where a separate regulatory speed limit applies, the relevant regulatory sign establishes that restriction.
Does W355 Require Drivers to Stop?
No. W355 does not itself require drivers to stop at the sign.
It warns that slow-moving or stationary traffic may be ahead, and drivers should be prepared to stop if the actual traffic conditions require it.
W355 and Following Distance
When approaching congestion, maintaining an appropriate following distance is important because traffic speed can change rapidly.
A suitable gap gives drivers additional time to respond when the queue slows or stops unexpectedly.
W355 and Sudden Braking
Congestion can result in sudden speed changes, particularly near the back of a queue.
W355 gives drivers advance warning so they can begin reducing speed before reaching the slower traffic rather than relying on heavy braking at the last moment.
W355 and Lane Changes
Drivers approaching congestion should remain alert for vehicles changing lanes as traffic begins to slow.
Sudden lane changes can occur when drivers attempt to move around slower traffic or when different lanes develop different speeds.
W355 and Overtaking
Congestion can make overtaking more difficult and may result in rapid changes in traffic speed.
Drivers should comply with the applicable road rules and should not make unsafe overtaking or lane-changing manoeuvres when approaching a queue.
W355 and Heavy Vehicles
Heavy vehicles require appropriate space to slow and stop.
Drivers of trucks, buses and other large vehicles approaching a congestion warning should allow sufficient distance to adjust to the queue ahead.
W355 and Motorcycles
Motorcyclists should also remain alert for rapidly changing traffic speeds and lane movements around congestion.
Reduced speed and careful observation are particularly important near the back of a traffic queue.
W355 and Cyclists
Cyclists travelling on or alongside roads where congestion occurs should remain aware of slow-moving, stationary and changing traffic conditions.
Drivers should also watch for cyclists who may be affected by the changing movement of vehicles around a queue.
W355 and Pedestrians
Pedestrians may encounter additional vehicle movements around congested areas, particularly where traffic queues form near intersections, commercial areas or public transport facilities.
Where a separate pedestrian hazard exists, the appropriate pedestrian-related signs and controls should also be considered.
W355 and Traffic Density
High traffic density can contribute to unstable traffic flow.
When the volume of traffic reaches a point where speeds reduce significantly or vehicles become stationary, congestion can become a hazard for approaching motorists.
W355 can provide advance warning in locations where this happens unpredictably.
W355 and Traffic Flow Instability
The SARTSM describes conditions where traffic flow becomes sufficiently unstable that there are significant reductions in speed or traffic comes to a stop.
These situations are particularly relevant to the recommended application of W355 on high-speed arterials and freeways.
W355 and Variable Message Signs
The SARTSM recommends the use of the temporary TW355 form as a variable-message sign in the conditions for which congestion warning is required.
A variable-message system can be updated as traffic conditions change, allowing road operators to warn approaching drivers when congestion develops.
TW355 Temporary Congestion Sign
TW355 is the temporary version of the W355 Congestion warning sign.
The temporary form is particularly useful where traffic congestion develops unpredictably and the warning needs to respond to changing conditions.
The SARTSM recommends the temporary form and variable-message-sign application for the high-speed road conditions described for W355.
TW355 and Variable Message Boards
Variable message boards can provide congestion warnings that change according to traffic conditions.
This can be useful when congestion develops because of an incident, unusual traffic demand, road restrictions or another changing situation.
The displayed warning should accurately reflect the traffic condition ahead.
W355 Permanent Sign
A permanent W355 sign may be used where the applicable conditions justify a fixed warning arrangement.
The SARTSM recommends that when the permanent sign is used, it should be displayed in advance of sections of normally free-flowing roadway where congestion is likely to occur.
A supplementary distance plate should indicate the distance over which the congestion is likely to occur.
W355 and IN11.2 Distance Plates
The SARTSM recommends an IN11.2 supplementary plate with a permanent W355 where appropriate.
The plate indicates the distance for which congestion is likely to occur.
This helps drivers understand whether the congestion is expected to affect only a short section or continue for a longer distance.
W355 and Long Congestion Queues
Traffic queues can extend for significant distances, particularly during major incidents or periods of unstable traffic flow.
Where a permanent W355 is used, the supplementary distance information should communicate the expected length of the congestion section in accordance with the applicable requirements.
W355 and Traffic Incidents
Road incidents can cause vehicles to slow or stop and may produce a congestion queue behind the incident.
Temporary congestion warning may be appropriate where approaching traffic cannot see the queue sufficiently far in advance.
Variable-message systems can be useful where available because the warning can be updated as the queue develops and clears.
W355 and Roadworks
Roadworks can reduce road capacity and create traffic queues.
Where the congestion itself becomes an unpredictable hazard, TW355 may form part of the temporary traffic-management arrangement.
Roadworks should still be signed with the appropriate roadworks warning and traffic-control signs where required.
W355 and Lane Closures
A lane closure can reduce available road capacity and cause traffic to slow or stop.
Appropriate lane-closure, roadworks and traffic-management signs should communicate the specific restriction.
Where an unpredictable congestion queue becomes an additional hazard, congestion warning may also be considered.
W355 and Freeway Queues
Freeways can carry high volumes of traffic at relatively high operating speeds.
A queue forming unexpectedly can therefore create a significant speed difference between approaching vehicles and stationary traffic.
This is one of the environments for which the SARTSM specifically recommends consideration of congestion warning.
W355 and Arterial Road Queues
High-speed arterial roads can also develop unstable traffic flow.
Where congestion occurs unpredictably and may require approaching drivers to significantly reduce speed or stop, W355 may be appropriate.
W355 and Daily Peak-Hour Traffic
A road that predictably becomes busy every morning or afternoon does not automatically require a permanent W355 sign.
The SARTSM focuses W355 on congestion that develops in an unpredictable or random manner, particularly where traffic flow becomes unstable.
Normal predictable traffic demand may require other traffic-management or transport-planning measures rather than a permanent W355 warning.
W355 and Predictable Congestion
Predictable congestion should be assessed differently from an unexpected traffic queue.
Permanent W355 is not intended to become a general “busy road” sign. The actual characteristics of the congestion and the road environment should determine whether the warning is appropriate.
W355 and Emergency Traffic Management
Emergency incidents can cause rapid changes in traffic flow.
Where a queue develops unexpectedly, temporary congestion warning can provide approaching motorists with information before they reach stationary traffic.
W355 and Variable Traffic Conditions
Traffic conditions can change according to incidents, weather, traffic demand, road capacity and other factors.
Variable-message signs can provide warnings that respond to these changing conditions where suitable traffic-management systems are available.
W355 Sign Placement
W355 should be positioned in advance of the congestion hazard.
General SARTSM guidance states that advance warning signs should normally be located according to the applicable Table 3.1 or Figure 3.1 requirements, taking account of operating speed and visibility.
Where a permanent W355 is used, it should be positioned in advance of the normally free-flowing roadway section where congestion is likely to occur.
W355 and Warning Distance
The correct warning distance depends on operating speed, road characteristics, available visibility and the location of the congestion hazard.
Where the warning sign is placed far enough from the hazard to provide adequate advance information, a supplementary distance plate can provide additional information about the affected section.
W355 and Clear Visibility
The warning sign should be visible to approaching road users from a sufficient distance.
If road alignment or other conditions restrict visibility, the sign may need to be positioned further from the hazard so that the required clear visibility distance is achieved.
W355 and Sign Size
The appropriate W355 sign size depends on the road environment and applicable traffic-sign requirements.
Factors that may influence the size include:
- Operating speed
- Road classification
- Traffic volume
- Required viewing distance
- Road alignment
- Background lighting
- Need for greater visual emphasis
The SARTSM provides standard triangular warning-sign sizes, with selection based on the circumstances of the installation.
Permanent W355 Sign Design and Colours
The permanent W355 warning sign uses the standard South African warning-sign arrangement:
- Triangle: Red retroreflective
- Symbol: Black semi-matt
- Background: White retroreflective
The symbol depicts a queue of vehicles to represent congestion ahead.
Temporary TW355 Sign Design and Colours
The temporary TW355 warning sign uses:
- Triangle: Red retroreflective
- Symbol: Black semi-matt
- Background: Yellow retroreflective
The yellow background identifies the sign as a temporary warning sign.
Retroreflective W355 Road Signs
Retroreflective materials help warning signs remain visible when illuminated by vehicle headlights.
The permanent W355 specification uses red and white retroreflective areas with a black semi-matt symbol, while the temporary sign uses a yellow retroreflective background.
For public-road applications, W355 and TW355 should be manufactured according to the applicable South African road traffic sign specifications.
W355 and High Visibility Backgrounds
Where greater visual emphasis is required, warning signs may be displayed on an appropriate high-visibility background in accordance with the applicable traffic-sign requirements.
The SARTSM allows warning signs to be displayed on high-visibility backgrounds where additional conspicuity is required.
W355 and Night-Time Visibility
Congestion can be more difficult to identify at night, especially when stationary vehicles are hidden by road alignment or darkness.
Retroreflective warning signage provides advance information when illuminated by vehicle headlights.
Drivers should still respond to the actual traffic conditions and not rely on the sign alone.
W355 Maintenance
W355 signs should be inspected and maintained so that they remain clean, visible and legible.
Maintenance checks can include:
- Cleaning the sign face
- Checking for fading
- Checking for physical damage
- Checking mounting hardware
- Removing vegetation or obstructions
- Checking retroreflective performance where applicable
Variable-message equipment associated with congestion warnings should also be maintained so that messages can be displayed correctly when required.
W355 and Traffic Monitoring
Traffic monitoring systems may be used by road operators to identify developing queues and unstable traffic flow.
Where variable-message systems are available, detected congestion can be communicated to approaching road users through suitable warnings.
W355 and Intelligent Transport Systems
Modern traffic-management systems can combine traffic monitoring, cameras, sensors and variable-message signs to communicate changing traffic conditions.
These systems can support the use of temporary congestion warnings where traffic conditions are unpredictable.
W355 and Variable Message Signs
A variable-message sign can display congestion information dynamically instead of relying only on a fixed warning sign.
This is particularly relevant to the SARTSM recommendation for the temporary form of W355 in high-speed road environments where congestion becomes unstable.
W355 on Public Roads in South Africa
On public roads, W355 and TW355 should be selected, positioned and installed according to the applicable South African road traffic sign requirements and the requirements of the responsible road authority.
The warning should correspond to actual congestion conditions and should be reviewed when the traffic situation changes.
W355 on Private Roads and Properties
Similar congestion-warning signage may also be useful on private roads and controlled properties where slow-moving or stationary traffic can create a traffic-management concern.
Potential applications include:
- Industrial facilities
- Warehouses
- Distribution centres
- Large commercial properties
- Events and venues
- Private estates
- Mining properties
- Construction compounds
- Large parking facilities
- Private access roads
On private property, the warning can form part of an internal traffic-management system based on the site's traffic conditions.
W355 at Industrial Facilities
Industrial properties can experience vehicle queues at entrances, security checkpoints, loading areas and dispatch points.
Where traffic becomes slow-moving or stationary and the queue presents a hazard to approaching vehicles, suitable congestion-warning signage may form part of the site's traffic-management system.
W355 at Warehouses and Distribution Centres
Warehouses and logistics facilities can experience queues of trucks and other vehicles during busy loading or receiving periods.
Where the queue creates a hazard on an access road or approaches a public road, suitable warning and traffic-management measures may be required.
W355 at Events and Venues
Large events can cause temporary traffic congestion around entrances, exits and parking facilities.
Temporary congestion warning can be used as part of an appropriate event traffic-management plan where queues create a hazard to approaching traffic.
W355 at Construction Sites
Construction sites can experience temporary queues caused by site access controls, deliveries, plant movements or roadworks.
Where slow-moving or stationary traffic becomes a hazard, suitable temporary congestion warning may be considered along with the other required traffic-management devices.
W355 at Mining Sites
Mining operations can produce significant vehicle movements and queues around access points, checkpoints and haul-road intersections.
Where congestion creates a relevant hazard, suitable internal traffic-management signage can help communicate the condition to approaching drivers.
W355 in Parking Facilities
Large parking facilities can experience queues at entrances, exits, payment points and security checkpoints.
Where traffic congestion creates a potential hazard, suitable warning signage can be incorporated into the internal traffic-management arrangement.
W355 and Public Transport Queues
Traffic congestion can develop around public transport facilities, taxi ranks, bus terminals and other high-activity areas.
Where the resulting vehicle queue creates a specific roadway hazard, appropriate traffic-management signs and controls should be considered.
W355 and Road Capacity
Congestion often develops when traffic demand approaches or exceeds the practical capacity of a road section.
When this results in unstable traffic flow, rapidly falling speeds or stationary traffic, approaching drivers may require advance warning.
W355 and Traffic Incidents
Vehicle crashes, disabled vehicles, lane restrictions and other incidents can produce sudden queues.
Temporary congestion warning can be useful where approaching traffic cannot see the resulting queue from a sufficient distance.
W355 and Road Closures
A road closure or major restriction can create traffic queues on the affected approach.
Other signs should communicate the closure or restriction itself. W355 can address the congestion hazard where the queue becomes an additional risk.
W355 and Diversions
A diversion can change the normal traffic pattern and increase congestion on an alternative route.
Where the temporary route develops an unpredictable congestion hazard, TW355 may be considered as part of the temporary traffic-management arrangement.
Who May Need W355 Traffic Congestion Signs?
W355 and TW355 signage may be relevant to:
- Road authorities
- Municipalities
- Traffic-management contractors
- Road maintenance contractors
- Road construction contractors
- Event traffic-management teams
- Industrial facility managers
- Warehouse and logistics operators
- Mining operations
- Property managers
- Commercial property owners
- Private estate managers
Benefits of W355 Traffic Congestion Warning Signs
- Warns drivers about slow-moving or stationary traffic ahead.
- Provides advance information before a developing traffic queue.
- Helps drivers prepare to reduce speed.
- Warns drivers that traffic may come to a stop.
- Can be useful where congestion develops unpredictably or randomly.
- Can be particularly relevant on high-speed arterials and freeways.
- TW355 can be used as part of a variable-message congestion warning system.
- A permanent W355 can be supplemented with distance information showing the likely length of congestion.
Frequently Asked Questions About W355 Road Signs
What does W355 mean?
W355 means Congestion. It warns about slow-moving or stationary traffic in the roadway ahead.
What is the official name of W355?
The official South African designation is CONGESTION.
What is W355 used for?
W355 is used to warn drivers about congestion ahead that may require a significant reduction in speed or stopping.
Does W355 mean traffic is completely stopped?
Not necessarily. W355 covers both slow-moving and stationary traffic.
Does W355 impose a speed limit?
No. W355 is a warning sign and does not itself establish a legal speed limit.
Does W355 require drivers to stop?
No. The sign warns that traffic may be stationary ahead, so drivers should be prepared to stop if the actual conditions require it.
When should W355 be used?
The SARTSM recommends W355 for sections where congestion occurs in an unpredictable or random manner and creates a hazard.
Is W355 intended for normal peak-hour traffic?
Not generally. The official guidance focuses on unpredictable or unstable congestion rather than simply a road being busy at predictable times.
Where is W355 particularly recommended?
The SARTSM recommends it particularly on normally high-speed arterials and freeways where traffic flow can become unstable.
What is TW355?
TW355 is the temporary version of the Congestion warning sign.
Can TW355 be used on a variable-message sign?
Yes. The SARTSM recommends the temporary W355 form as a variable-message sign for the relevant high-speed congestion conditions.
Why are variable-message signs useful for congestion?
They can provide warnings that change as traffic conditions develop, which is useful for unpredictable congestion.
Can a permanent W355 sign be used?
Yes, where the applicable conditions justify it. The SARTSM recommends a permanent W355 with supplementary distance information.
What is the IN11.2 plate used for with W355?
It indicates the distance for which congestion is likely to occur.
Can W355 warn about a traffic queue around a bend?
Yes. Limited visibility caused by road alignment can contribute to the congestion hazard addressed by W355.
Can W355 be used near a roadworks site?
Temporary congestion warning may be appropriate where roadworks create unpredictable traffic queues, together with the required roadworks and traffic-control signs.
Can W355 be used after a traffic accident?
Temporary congestion warning may be appropriate where an incident creates a queue that is difficult for approaching traffic to see in time.
Can W355 be used at a freeway?
Yes. Freeways are specifically identified among the road types where W355 may be appropriate when congestion becomes unstable.
Can W355 be used on an arterial road?
Yes. High-speed arterial roads are also identified as possible applications where unpredictable congestion creates a hazard.
Can W355 be used on a private road?
Similar congestion warning signage can be used on private roads and controlled properties where queues create a traffic-management concern.
Can W355 be used at a warehouse?
Similar warning signage may be useful where truck or vehicle queues create a hazard around warehouse entrances and access roads.
Can W355 be used at an event?
Temporary congestion warning may form part of an event traffic-management plan where vehicle queues create a hazard.
What colours does permanent W355 use?
Permanent W355 uses a red retroreflective triangle, black semi-matt symbol and white retroreflective background.
What colours does TW355 use?
TW355 uses a red retroreflective triangle, black semi-matt symbol and yellow retroreflective background.
What should drivers do when they see W355?
Drivers should reduce speed, watch for slow or stationary traffic, maintain a safe following distance and be prepared to stop.
Can W355 be used for every traffic jam?
No. The SARTSM specifically focuses W355 on unpredictable or random congestion that creates a hazard, particularly on normally high-speed roads.
Can W355 be combined with other road signs?
Yes. Other warning, regulatory and temporary traffic-management signs may be required depending on the cause of the congestion.
Is W355 a warning sign?
Yes. W355 belongs to the South African W-series warning signs.
Can Signs4SA supply W355 signs?
Yes. Signs4SA can assist with W355 Traffic Congestion signs, temporary TW355 signs, supplementary distance plates and related traffic-management signage.
Order W355 Traffic Congestion Warning Signs
Need W355 Traffic Congestion or TW355 Temporary Congestion signs for a freeway, arterial road, roadworks project, traffic incident, event, industrial property, warehouse, private road or traffic-management application?
Signs4SA can assist with permanent and temporary congestion warning signage and supplementary traffic-sign products for different road and traffic-management applications.
Contact Signs4SA with the W355 or TW355 code, required quantity, sign size, material, supplementary message and installation requirements to request a quotation.
One important feature of Traffic congestion ahead signs is their high visibility. These signs are designed to be easily seen by drivers, even from a distance and in adverse weather conditions. Many Traffic congestion ahead signs are also designed with reflective materials that make them visible at night.
Another important feature of Traffic congestion ahead signs is their durability. Road signs are exposed to a wide range of environmental factors, including wind, rain, and extreme temperatures. As such, they need to be made from materials that can withstand these conditions and remain in good condition for years to come.
More About Traffic congestion ahead
Traffic Congestion Ahead – W355 Road Sign
The W355 Traffic Congestion Ahead road sign is a South African warning sign used to alert drivers and other road users to the possibility of slow-moving or stationary traffic ahead.
The official South African road traffic sign designation is W355 CONGESTION. The warning is intended for situations where traffic congestion may become a hazard because of traffic density or limited visibility caused by road alignment, and where drivers may need to significantly reduce speed or stop.
W355 is particularly relevant on normally free-flowing, higher-speed roads where congestion can develop unexpectedly and create a queue that approaching drivers may not see in sufficient time.
What Does the W355 Road Sign Mean?
W355 means Congestion. It warns drivers that slow-moving or stationary traffic may be present on the roadway ahead.
The sign is intended to give approaching drivers advance warning of a traffic queue or unstable traffic flow so that they can reduce speed and prepare for the possibility of coming to a stop.
W355 is a warning sign. It does not itself impose a particular speed limit or require drivers to stop at the sign.
Why Is the W355 Traffic Congestion Sign Important?
Traffic queues can develop quickly, especially on high-speed roads.
A driver travelling at normal operating speed may encounter a stationary or very slow-moving queue around a bend, over a crest or further ahead because of traffic density.
W355 provides advance warning of this possibility so drivers can begin reducing speed before reaching the back of the queue.
This is particularly important where the queue cannot be seen clearly from a long distance.
When Is W355 Used?
The SARTSM states that W355 is used to warn drivers of the possibility of slow-moving or stationary traffic in the roadway ahead where it may constitute a hazard and may require the driver to significantly reduce speed or stop.
W355 should be displayed in advance of sections where congestion occurs in an unpredictable or random manner.
This distinction is important because not every busy road or normal peak-period traffic queue automatically requires W355.
W355 and Unpredictable Traffic Congestion
The official guidance focuses on congestion that develops in an unpredictable or random way.
Where traffic flow can suddenly become unstable and speeds can fall significantly, approaching drivers may not have enough time to respond if there is no advance warning.
W355 is intended for these types of situations rather than being a general sign for every road that experiences traffic during busy periods.
W355 and Freeways
The SARTSM recommends W355 particularly for normally high-speed arterials and freeways where congestion can become unstable enough to cause significant reductions in speed or bring traffic to a stop.
These roads can present a greater difference between normal operating speed and the speed of a developing traffic queue.
An approaching driver may therefore require additional warning to reduce speed progressively.
W355 and High-Speed Arterial Roads
High-speed arterial roads can also experience sudden congestion caused by traffic demand, incidents, road restrictions and other changing conditions.
Where congestion occurs unpredictably and presents a meaningful hazard to approaching traffic, W355 may be appropriate.
W355 and Stationary Traffic
W355 includes situations where traffic may be stationary.
A stationary queue can present a serious hazard when approaching traffic is travelling much faster and has limited sight distance to the back of the queue.
The purpose of the warning is to give drivers additional time to slow down before encountering stopped vehicles.
W355 and Slow-Moving Traffic
Traffic does not have to be completely stopped for W355 to be relevant.
The sign also warns about slow-moving traffic where the reduction in speed is significant enough to create a hazard or require drivers to make a substantial speed adjustment.
W355 and Limited Visibility
The SARTSM identifies limited visibility due to road alignment or traffic density as factors that can contribute to the congestion hazard.
For example, a queue may be hidden around a bend or beyond a crest, giving approaching drivers less time to react.
W355 and Road Curves
A traffic queue around a curve may not be visible to approaching drivers until they are relatively close to the stationary vehicles.
W355 can provide advance information before the curve or affected section where the congestion hazard is likely to occur.
W355 and Road Crests
A crest can hide slow-moving or stationary traffic from approaching drivers.
Where congestion regularly develops beyond a crest in an unpredictable manner and creates a relevant hazard, advance congestion warning may be considered.
How Should Drivers Respond to W355?
Drivers approaching a W355 sign should expect slow-moving or stationary traffic ahead and adjust their driving accordingly.
Drivers should:
- Reduce speed progressively.
- Look ahead for the back of the traffic queue.
- Maintain a suitable following distance.
- Be prepared to stop.
- Watch for sudden braking by vehicles ahead.
- Remain alert for lane changes by other drivers.
- Follow variable-message signs and other traffic controls.
- Avoid sudden manoeuvres.
The correct response depends on the actual traffic speed, queue length, road conditions and visibility.
Does W355 Set a Speed Limit?
No. W355 is a warning sign and does not itself establish a legal speed limit.
Its purpose is to warn drivers that congestion may require a significant reduction in speed or may result in traffic coming to a stop.
Where a separate regulatory speed limit applies, the relevant regulatory sign establishes that restriction.
Does W355 Require Drivers to Stop?
No. W355 does not itself require drivers to stop at the sign.
It warns that slow-moving or stationary traffic may be ahead, and drivers should be prepared to stop if the actual traffic conditions require it.
W355 and Following Distance
When approaching congestion, maintaining an appropriate following distance is important because traffic speed can change rapidly.
A suitable gap gives drivers additional time to respond when the queue slows or stops unexpectedly.
W355 and Sudden Braking
Congestion can result in sudden speed changes, particularly near the back of a queue.
W355 gives drivers advance warning so they can begin reducing speed before reaching the slower traffic rather than relying on heavy braking at the last moment.
W355 and Lane Changes
Drivers approaching congestion should remain alert for vehicles changing lanes as traffic begins to slow.
Sudden lane changes can occur when drivers attempt to move around slower traffic or when different lanes develop different speeds.
W355 and Overtaking
Congestion can make overtaking more difficult and may result in rapid changes in traffic speed.
Drivers should comply with the applicable road rules and should not make unsafe overtaking or lane-changing manoeuvres when approaching a queue.
W355 and Heavy Vehicles
Heavy vehicles require appropriate space to slow and stop.
Drivers of trucks, buses and other large vehicles approaching a congestion warning should allow sufficient distance to adjust to the queue ahead.
W355 and Motorcycles
Motorcyclists should also remain alert for rapidly changing traffic speeds and lane movements around congestion.
Reduced speed and careful observation are particularly important near the back of a traffic queue.
W355 and Cyclists
Cyclists travelling on or alongside roads where congestion occurs should remain aware of slow-moving, stationary and changing traffic conditions.
Drivers should also watch for cyclists who may be affected by the changing movement of vehicles around a queue.
W355 and Pedestrians
Pedestrians may encounter additional vehicle movements around congested areas, particularly where traffic queues form near intersections, commercial areas or public transport facilities.
Where a separate pedestrian hazard exists, the appropriate pedestrian-related signs and controls should also be considered.
W355 and Traffic Density
High traffic density can contribute to unstable traffic flow.
When the volume of traffic reaches a point where speeds reduce significantly or vehicles become stationary, congestion can become a hazard for approaching motorists.
W355 can provide advance warning in locations where this happens unpredictably.
W355 and Traffic Flow Instability
The SARTSM describes conditions where traffic flow becomes sufficiently unstable that there are significant reductions in speed or traffic comes to a stop.
These situations are particularly relevant to the recommended application of W355 on high-speed arterials and freeways.
W355 and Variable Message Signs
The SARTSM recommends the use of the temporary TW355 form as a variable-message sign in the conditions for which congestion warning is required.
A variable-message system can be updated as traffic conditions change, allowing road operators to warn approaching drivers when congestion develops.
TW355 Temporary Congestion Sign
TW355 is the temporary version of the W355 Congestion warning sign.
The temporary form is particularly useful where traffic congestion develops unpredictably and the warning needs to respond to changing conditions.
The SARTSM recommends the temporary form and variable-message-sign application for the high-speed road conditions described for W355.
TW355 and Variable Message Boards
Variable message boards can provide congestion warnings that change according to traffic conditions.
This can be useful when congestion develops because of an incident, unusual traffic demand, road restrictions or another changing situation.
The displayed warning should accurately reflect the traffic condition ahead.
W355 Permanent Sign
A permanent W355 sign may be used where the applicable conditions justify a fixed warning arrangement.
The SARTSM recommends that when the permanent sign is used, it should be displayed in advance of sections of normally free-flowing roadway where congestion is likely to occur.
A supplementary distance plate should indicate the distance over which the congestion is likely to occur.
W355 and IN11.2 Distance Plates
The SARTSM recommends an IN11.2 supplementary plate with a permanent W355 where appropriate.
The plate indicates the distance for which congestion is likely to occur.
This helps drivers understand whether the congestion is expected to affect only a short section or continue for a longer distance.
W355 and Long Congestion Queues
Traffic queues can extend for significant distances, particularly during major incidents or periods of unstable traffic flow.
Where a permanent W355 is used, the supplementary distance information should communicate the expected length of the congestion section in accordance with the applicable requirements.
W355 and Traffic Incidents
Road incidents can cause vehicles to slow or stop and may produce a congestion queue behind the incident.
Temporary congestion warning may be appropriate where approaching traffic cannot see the queue sufficiently far in advance.
Variable-message systems can be useful where available because the warning can be updated as the queue develops and clears.
W355 and Roadworks
Roadworks can reduce road capacity and create traffic queues.
Where the congestion itself becomes an unpredictable hazard, TW355 may form part of the temporary traffic-management arrangement.
Roadworks should still be signed with the appropriate roadworks warning and traffic-control signs where required.
W355 and Lane Closures
A lane closure can reduce available road capacity and cause traffic to slow or stop.
Appropriate lane-closure, roadworks and traffic-management signs should communicate the specific restriction.
Where an unpredictable congestion queue becomes an additional hazard, congestion warning may also be considered.
W355 and Freeway Queues
Freeways can carry high volumes of traffic at relatively high operating speeds.
A queue forming unexpectedly can therefore create a significant speed difference between approaching vehicles and stationary traffic.
This is one of the environments for which the SARTSM specifically recommends consideration of congestion warning.
W355 and Arterial Road Queues
High-speed arterial roads can also develop unstable traffic flow.
Where congestion occurs unpredictably and may require approaching drivers to significantly reduce speed or stop, W355 may be appropriate.
W355 and Daily Peak-Hour Traffic
A road that predictably becomes busy every morning or afternoon does not automatically require a permanent W355 sign.
The SARTSM focuses W355 on congestion that develops in an unpredictable or random manner, particularly where traffic flow becomes unstable.
Normal predictable traffic demand may require other traffic-management or transport-planning measures rather than a permanent W355 warning.
W355 and Predictable Congestion
Predictable congestion should be assessed differently from an unexpected traffic queue.
Permanent W355 is not intended to become a general “busy road” sign. The actual characteristics of the congestion and the road environment should determine whether the warning is appropriate.
W355 and Emergency Traffic Management
Emergency incidents can cause rapid changes in traffic flow.
Where a queue develops unexpectedly, temporary congestion warning can provide approaching motorists with information before they reach stationary traffic.
W355 and Variable Traffic Conditions
Traffic conditions can change according to incidents, weather, traffic demand, road capacity and other factors.
Variable-message signs can provide warnings that respond to these changing conditions where suitable traffic-management systems are available.
W355 Sign Placement
W355 should be positioned in advance of the congestion hazard.
General SARTSM guidance states that advance warning signs should normally be located according to the applicable Table 3.1 or Figure 3.1 requirements, taking account of operating speed and visibility.
Where a permanent W355 is used, it should be positioned in advance of the normally free-flowing roadway section where congestion is likely to occur.
W355 and Warning Distance
The correct warning distance depends on operating speed, road characteristics, available visibility and the location of the congestion hazard.
Where the warning sign is placed far enough from the hazard to provide adequate advance information, a supplementary distance plate can provide additional information about the affected section.
W355 and Clear Visibility
The warning sign should be visible to approaching road users from a sufficient distance.
If road alignment or other conditions restrict visibility, the sign may need to be positioned further from the hazard so that the required clear visibility distance is achieved.
W355 and Sign Size
The appropriate W355 sign size depends on the road environment and applicable traffic-sign requirements.
Factors that may influence the size include:
- Operating speed
- Road classification
- Traffic volume
- Required viewing distance
- Road alignment
- Background lighting
- Need for greater visual emphasis
The SARTSM provides standard triangular warning-sign sizes, with selection based on the circumstances of the installation.
Permanent W355 Sign Design and Colours
The permanent W355 warning sign uses the standard South African warning-sign arrangement:
- Triangle: Red retroreflective
- Symbol: Black semi-matt
- Background: White retroreflective
The symbol depicts a queue of vehicles to represent congestion ahead.
Temporary TW355 Sign Design and Colours
The temporary TW355 warning sign uses:
- Triangle: Red retroreflective
- Symbol: Black semi-matt
- Background: Yellow retroreflective
The yellow background identifies the sign as a temporary warning sign.
Retroreflective W355 Road Signs
Retroreflective materials help warning signs remain visible when illuminated by vehicle headlights.
The permanent W355 specification uses red and white retroreflective areas with a black semi-matt symbol, while the temporary sign uses a yellow retroreflective background.
For public-road applications, W355 and TW355 should be manufactured according to the applicable South African road traffic sign specifications.
W355 and High Visibility Backgrounds
Where greater visual emphasis is required, warning signs may be displayed on an appropriate high-visibility background in accordance with the applicable traffic-sign requirements.
The SARTSM allows warning signs to be displayed on high-visibility backgrounds where additional conspicuity is required.
W355 and Night-Time Visibility
Congestion can be more difficult to identify at night, especially when stationary vehicles are hidden by road alignment or darkness.
Retroreflective warning signage provides advance information when illuminated by vehicle headlights.
Drivers should still respond to the actual traffic conditions and not rely on the sign alone.
W355 Maintenance
W355 signs should be inspected and maintained so that they remain clean, visible and legible.
Maintenance checks can include:
- Cleaning the sign face
- Checking for fading
- Checking for physical damage
- Checking mounting hardware
- Removing vegetation or obstructions
- Checking retroreflective performance where applicable
Variable-message equipment associated with congestion warnings should also be maintained so that messages can be displayed correctly when required.
W355 and Traffic Monitoring
Traffic monitoring systems may be used by road operators to identify developing queues and unstable traffic flow.
Where variable-message systems are available, detected congestion can be communicated to approaching road users through suitable warnings.
W355 and Intelligent Transport Systems
Modern traffic-management systems can combine traffic monitoring, cameras, sensors and variable-message signs to communicate changing traffic conditions.
These systems can support the use of temporary congestion warnings where traffic conditions are unpredictable.
W355 and Variable Message Signs
A variable-message sign can display congestion information dynamically instead of relying only on a fixed warning sign.
This is particularly relevant to the SARTSM recommendation for the temporary form of W355 in high-speed road environments where congestion becomes unstable.
W355 on Public Roads in South Africa
On public roads, W355 and TW355 should be selected, positioned and installed according to the applicable South African road traffic sign requirements and the requirements of the responsible road authority.
The warning should correspond to actual congestion conditions and should be reviewed when the traffic situation changes.
W355 on Private Roads and Properties
Similar congestion-warning signage may also be useful on private roads and controlled properties where slow-moving or stationary traffic can create a traffic-management concern.
Potential applications include:
- Industrial facilities
- Warehouses
- Distribution centres
- Large commercial properties
- Events and venues
- Private estates
- Mining properties
- Construction compounds
- Large parking facilities
- Private access roads
On private property, the warning can form part of an internal traffic-management system based on the site's traffic conditions.
W355 at Industrial Facilities
Industrial properties can experience vehicle queues at entrances, security checkpoints, loading areas and dispatch points.
Where traffic becomes slow-moving or stationary and the queue presents a hazard to approaching vehicles, suitable congestion-warning signage may form part of the site's traffic-management system.
W355 at Warehouses and Distribution Centres
Warehouses and logistics facilities can experience queues of trucks and other vehicles during busy loading or receiving periods.
Where the queue creates a hazard on an access road or approaches a public road, suitable warning and traffic-management measures may be required.
W355 at Events and Venues
Large events can cause temporary traffic congestion around entrances, exits and parking facilities.
Temporary congestion warning can be used as part of an appropriate event traffic-management plan where queues create a hazard to approaching traffic.
W355 at Construction Sites
Construction sites can experience temporary queues caused by site access controls, deliveries, plant movements or roadworks.
Where slow-moving or stationary traffic becomes a hazard, suitable temporary congestion warning may be considered along with the other required traffic-management devices.
W355 at Mining Sites
Mining operations can produce significant vehicle movements and queues around access points, checkpoints and haul-road intersections.
Where congestion creates a relevant hazard, suitable internal traffic-management signage can help communicate the condition to approaching drivers.
W355 in Parking Facilities
Large parking facilities can experience queues at entrances, exits, payment points and security checkpoints.
Where traffic congestion creates a potential hazard, suitable warning signage can be incorporated into the internal traffic-management arrangement.
W355 and Public Transport Queues
Traffic congestion can develop around public transport facilities, taxi ranks, bus terminals and other high-activity areas.
Where the resulting vehicle queue creates a specific roadway hazard, appropriate traffic-management signs and controls should be considered.
W355 and Road Capacity
Congestion often develops when traffic demand approaches or exceeds the practical capacity of a road section.
When this results in unstable traffic flow, rapidly falling speeds or stationary traffic, approaching drivers may require advance warning.
W355 and Traffic Incidents
Vehicle crashes, disabled vehicles, lane restrictions and other incidents can produce sudden queues.
Temporary congestion warning can be useful where approaching traffic cannot see the resulting queue from a sufficient distance.
W355 and Road Closures
A road closure or major restriction can create traffic queues on the affected approach.
Other signs should communicate the closure or restriction itself. W355 can address the congestion hazard where the queue becomes an additional risk.
W355 and Diversions
A diversion can change the normal traffic pattern and increase congestion on an alternative route.
Where the temporary route develops an unpredictable congestion hazard, TW355 may be considered as part of the temporary traffic-management arrangement.
Who May Need W355 Traffic Congestion Signs?
W355 and TW355 signage may be relevant to:
- Road authorities
- Municipalities
- Traffic-management contractors
- Road maintenance contractors
- Road construction contractors
- Event traffic-management teams
- Industrial facility managers
- Warehouse and logistics operators
- Mining operations
- Property managers
- Commercial property owners
- Private estate managers
Benefits of W355 Traffic Congestion Warning Signs
- Warns drivers about slow-moving or stationary traffic ahead.
- Provides advance information before a developing traffic queue.
- Helps drivers prepare to reduce speed.
- Warns drivers that traffic may come to a stop.
- Can be useful where congestion develops unpredictably or randomly.
- Can be particularly relevant on high-speed arterials and freeways.
- TW355 can be used as part of a variable-message congestion warning system.
- A permanent W355 can be supplemented with distance information showing the likely length of congestion.
Frequently Asked Questions About W355 Road Signs
What does W355 mean?
W355 means Congestion. It warns about slow-moving or stationary traffic in the roadway ahead.
What is the official name of W355?
The official South African designation is CONGESTION.
What is W355 used for?
W355 is used to warn drivers about congestion ahead that may require a significant reduction in speed or stopping.
Does W355 mean traffic is completely stopped?
Not necessarily. W355 covers both slow-moving and stationary traffic.
Does W355 impose a speed limit?
No. W355 is a warning sign and does not itself establish a legal speed limit.
Does W355 require drivers to stop?
No. The sign warns that traffic may be stationary ahead, so drivers should be prepared to stop if the actual conditions require it.
When should W355 be used?
The SARTSM recommends W355 for sections where congestion occurs in an unpredictable or random manner and creates a hazard.
Is W355 intended for normal peak-hour traffic?
Not generally. The official guidance focuses on unpredictable or unstable congestion rather than simply a road being busy at predictable times.
Where is W355 particularly recommended?
The SARTSM recommends it particularly on normally high-speed arterials and freeways where traffic flow can become unstable.
What is TW355?
TW355 is the temporary version of the Congestion warning sign.
Can TW355 be used on a variable-message sign?
Yes. The SARTSM recommends the temporary W355 form as a variable-message sign for the relevant high-speed congestion conditions.
Why are variable-message signs useful for congestion?
They can provide warnings that change as traffic conditions develop, which is useful for unpredictable congestion.
Can a permanent W355 sign be used?
Yes, where the applicable conditions justify it. The SARTSM recommends a permanent W355 with supplementary distance information.
What is the IN11.2 plate used for with W355?
It indicates the distance for which congestion is likely to occur.
Can W355 warn about a traffic queue around a bend?
Yes. Limited visibility caused by road alignment can contribute to the congestion hazard addressed by W355.
Can W355 be used near a roadworks site?
Temporary congestion warning may be appropriate where roadworks create unpredictable traffic queues, together with the required roadworks and traffic-control signs.
Can W355 be used after a traffic accident?
Temporary congestion warning may be appropriate where an incident creates a queue that is difficult for approaching traffic to see in time.
Can W355 be used at a freeway?
Yes. Freeways are specifically identified among the road types where W355 may be appropriate when congestion becomes unstable.
Can W355 be used on an arterial road?
Yes. High-speed arterial roads are also identified as possible applications where unpredictable congestion creates a hazard.
Can W355 be used on a private road?
Similar congestion warning signage can be used on private roads and controlled properties where queues create a traffic-management concern.
Can W355 be used at a warehouse?
Similar warning signage may be useful where truck or vehicle queues create a hazard around warehouse entrances and access roads.
Can W355 be used at an event?
Temporary congestion warning may form part of an event traffic-management plan where vehicle queues create a hazard.
What colours does permanent W355 use?
Permanent W355 uses a red retroreflective triangle, black semi-matt symbol and white retroreflective background.
What colours does TW355 use?
TW355 uses a red retroreflective triangle, black semi-matt symbol and yellow retroreflective background.
What should drivers do when they see W355?
Drivers should reduce speed, watch for slow or stationary traffic, maintain a safe following distance and be prepared to stop.
Can W355 be used for every traffic jam?
No. The SARTSM specifically focuses W355 on unpredictable or random congestion that creates a hazard, particularly on normally high-speed roads.
Can W355 be combined with other road signs?
Yes. Other warning, regulatory and temporary traffic-management signs may be required depending on the cause of the congestion.
Is W355 a warning sign?
Yes. W355 belongs to the South African W-series warning signs.
Can Signs4SA supply W355 signs?
Yes. Signs4SA can assist with W355 Traffic Congestion signs, temporary TW355 signs, supplementary distance plates and related traffic-management signage.
Order W355 Traffic Congestion Warning Signs
Need W355 Traffic Congestion or TW355 Temporary Congestion signs for a freeway, arterial road, roadworks project, traffic incident, event, industrial property, warehouse, private road or traffic-management application?
Signs4SA can assist with permanent and temporary congestion warning signage and supplementary traffic-sign products for different road and traffic-management applications.
Contact Signs4SA with the W355 or TW355 code, required quantity, sign size, material, supplementary message and installation requirements to request a quotation.
One popular type of road sign is the Traffic congestion ahead sign. This type of sign is used to provide drivers with important information about the road ahead, such as directions, speed limits, and potential hazards.
Traffic congestion ahead_ signs come in a variety of shapes and sizes, and are made from a range of materials, including metal, plastic, and reflective materials. They can be customized to meet the specific needs of a particular roadway or location, including the addition of logos, graphics, and text.
One important feature of Traffic congestion ahead signs is their high visibility. These signs are designed to be easily seen by drivers, even from a distance and in adverse weather conditions. Many Traffic congestion ahead signs are also designed with reflective materials that make them visible at night.
Another important feature of Traffic congestion ahead signs is their durability. Road signs are exposed to a wide range of environmental factors, including wind, rain, and extreme temperatures. As such, they need to be made from materials that can withstand these conditions and remain in good condition for years to come.
For businesses and organizations that need to create custom road signs, working with a reputable sign company can ensure that their signs are of high quality and meet all necessary standards and regulations. Signs4sa can provide expert advice on design, materials, and installation, and can help businesses ensure that their signs are installed safely and effectively.
Overall, Traffic congestion ahead signs are an important tool for ensuring road safety and providing drivers with the information they need to navigate effectively. By working with a professional sign company to create and install these signs, businesses and organizations can help ensure that their messages are seen and understood by drivers, and help to improve safety on the road.