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  • ask a question about traffic management

Make a traffic management enquiry

We are the Highway and Traffic Authority. That means we have a variety of traffic calming and management measures to use on the public highway.

Traffic calming and management 

Traffic calming measures aim to reduce vehicle speeds. They help to:

  • reduce the number and severity of road traffic accidents, and
  • discourage drivers from cutting through residential side roads

Traffic management are physical measures to restrict traffic movement. These measures need a Traffic Management Order, which can then be legally enforced by the Police.

Speed cameras 

London Safety Camera Partnership (LSCP) handles speed cameras in London. They install and operate them under strict guidelines. LSCP will only install speed cameras if there is a collision history of 4 people 'killed or seriously injured' (KSI) in collisions. These need to have happened the the last 36 months and 2 must be speed related.

Advantages

  • self enforcing and visible
  • popular with 90% support to reduce speed 
  • proven 50% reduction in casualties at safety camera sites installed by LSCP

Disadvantages

  • expensive
  • not practical for all roads 
  • perceived by some as a way of raising funds
  • less or no effect beyond the camera
  • are subject to vandalism
  • need regular maintenance

Central island refuge

Installation of traffic islands along the centre of the roads is generally used as:

  • a speed reducing measure
  • providing a pedestrian refuge facility to cross the road

Advantages

  • can provide a pedestrian facility where it is not possible to install a formal crossing
  • can be used to narrow the carriageway and prevent overtaking especially when used in a series, linked with centre hatching
  • do not affect the emergency services
  • can provide a protected right turn lane at junctions
  • provides protection to the adjacent lane

Disadvantages

  • limited speed-reducing effect compared with vertical deflection
  • loss of on-street parking

Mini-roundabout

Advantages

  • breaks up the flow of ‘through traffic’, slowing traffic on all approaches to the junction
  • may improve turning movements into and out of minor roads

Disadvantages

  • may not be effective in reducing speed of traffic if no deflection is possible
  • turning movements may serve to encourage more traffic onto side roads
  • if no islands are available, pedestrians find it difficult to cross the junction

Priority give-way (with priority provision for cyclists)

Advantages

  • utilises horizontal rather than vertical deflection so do not affect emergency services

Disadvantages

  • doesn't reduce vehicle speed unless the chicane is tight, this isn't possible to achieve for lorries and buses
  • some drivers see chicanes as a challenge and accelerate to get through
  • expensive to construct, especially if drainage works are necessary.
  • large loss of on-street parking

Junction table or entry treatment

Advantages

  • more acceptable to emergency services and bus operators than standard humps
  • slows down all approaching traffic to all arms of the junction
  • can be used in isolation and they do not have to form part of a series of road humps

Disadvantages

  • expensive to construct
  • construction may cause temporary traffic disruption
  • often requires temporary road closures
  • if constructed at footway height this can lead to confusion between motorists and pedestrians about who has right of way

Road narrowing (throttle)

Advantages

  • interrupts through traffic movement thereby reducing speed
  • does not delay emergency service vehicles or affect bus operation
  • cycle gaps can sometimes be incorporated
  • if cycle gap is not provided they can make safer crossing places for pedestrians

Disadvantages

  • limited speed-reducing effect - some vehicles increase speed to get through the narrowing before an oncoming vehicle
  • expensive if drainage works are necessary
  • loss of on-street parking

Round or flat top hump

Advantages

  • reasonably inexpensive to install
  • minimal disruption to traffic during construction
  • no loss of on-street parking
  • proven to be effective at reducing vehicle speeds

Disadvantages

  • result in an increase in emergency service response time
  • unsuitable on bus routes unless 65mm or lower
  • claims of increased noise and pollution, damage to vehicles and discomfort to occupants
  • can cause confusion between motorists and pedestrians about who has right of way
  • humps with block-work tops and/or those that span kerb to kerb are much more expensive to construct
  • can have drainage difficulty if constructed kerb-to-kerb

Speed cushions (pillow hump)

Advantages

  • accepted by emergency services
  • accepted by bus operators
  • inexpensive to construct
  • no loss of on-street parking
  • cyclists can pass between cushions

Disadvantages

  • if there are two cushions and on-street parking, vehicles may not be able to straddle the cushions - negating the benefits to the emergency services and buses
  • yellow line restrictions need to protect the cushions so that vehicles can straddle them, this would then result in a loss of on-street parking
  • less effective at speed reduction than conventional speed humps

Vehicle Activated Sign (VAS)

VAS signs display the speed limit when approached more than the speed limit. It flashes ‘SLOW’ message to inform the driver of their excess speed. Different types of VAS are currently in use, displaying other messages:

  • the speed of the approaching vehicle
  • a bright smiley face when approached below the speed limit
  • a red angry face if the approaching speed is more than the speed limit

VAS signs are sometimes accompanied by ‘wig wags’ (flashing amber lights). These are usually near schools, to make the sign more prominent. 

Advantages

  • simple, clear and easy for motorists to understand
  • suitable for a wide range of locations & installation types
  • can be set to display different speed limit, increasing their flexibility
  • useful in areas with a persistent speed problem
  • can be large, prominent and highly visible

Disadvantages

  • expensive to install
  • needs regular maintenance
  • does not give motorists the reason of the need to slow down
  • needs a dedicated mains power supply 
  • can be visually intrusive 

20mph zone

A 20mph zone is put in place when it can be proved that average speeds have been reduced to below 24mph. A 20mph zone should be self enforcing and effective, so it would be necessary to install traffic calming measures within the zone. 

Advantages

  • can include any of the different forms of the traffic calming measures so are easier to overcome localised site restrictions 
  • reduction in the amount of signing required
  • regular and repeated traffic calming measures will maintain low and steady speed through the zone

Disadvantages

  • requires traffic calming measures and this is not always popular with some residents
  • difficult to control and enforce without traffic calming measure