Road Narrowing

Road narrowed with bollards

Road narrowing simply reduces the width of the road. This can be achieved through physical measures such as kerb buildouts or central islands, or the use of coloured surfacing or road markings (sometimes called psychological traffic calming).  The treatment most commonly used in Cambridgeshire is the construction a buildout at each side of the road.  This can be combined with a pedestrian crossing point as it helps pedestrians cross the road more easily.  In this case, the kerb is dropped with tactile paving where the pavement slopes towards the road.

Drivers will need to drive more carefully in a narrowed section of road to keep their vehicle in the correct road position, which may result in slower vehicle speeds.

Effectiveness

Narrowings are a horizontal treatment that can reduce vehicle speeds.  Reducing vehicle speeds increases safety because:

  • The vehicle has travelled a shorter distance by the time a driver can react to a hazard
  • Braking distance is reduced, so the vehicle can stop more quickly before a hazard
  • Higher speed crashes tend to result in higher severity injuries
Advantages Disadvantages
  • Targets a specific part of the road
  • Can prevent vehicle parking
  • Make it easier for pedestrians to cross
  • Emergency vehicles should be able to pass without slowing down
  • Not as effective as vertical treatments
  • Managing water drainage could be complex and costly
  • Cyclists may feel intimidated by some vehicle drivers' behaviour at road narrowing
  • Can resemble a sheltered parking bay and encourage parking each side which can mask pedestrians.

Restrictions

Cost

Equipment:  £3,000 - £6,000
Works:  £2,500 - £4,500
Road Safety Audit:       £1,500
Traffic Regulation Order £1,000
Total£7,000 - £12,000
Costs vary depending on location, condition of existing road surface and drainage


Priority Narrowing

Road narrowing and priority give way to upcoming traffic sign at entrance to village

Priority narrowings require one direction of traffic to give way to oncoming vehicles. The narrowing consists of a build out and bollard in one half of the road or built out slightly from both sides, with a sign to show who has priority. For the lane without priority, there are Give Way markings on the approach.

Groups of narrowings can be placed with alternating priority down a road, so that each direction of vehicle traffic may have to stop and give priority in equal measures.

Effectiveness

Priority narrowings are a horizontal treatment which can reduce vehicle speeds. Vertical treatments - such as speed cushions or speed tables - are more effective at consistently keeping speeds lower over a longer length.

Reducing vehicle speeds increases safety because:

  • The vehicle has travelled a shorter distance by the time a driver can react to a hazard
  • Braking distance is reduced, so the vehicle can stop more quickly before a hazard
  • Higher speed crashes tend to result in higher severity injuries
Image example of a priority way sign

Example of a priority way sign

Advantages Disadvantages
  • Do not cause any vehicle passenger discomfort (in comparison to vertical treatments)
  • If there is sufficient road width they can be designed to allow cyclists to bypass them
  • Emergency vehicles may be able to travel faster around a narrowing compared to vertical treatments
  • Motor vehicles with priority are not required to reduce their speed
  • Motor vehicles without priority are not required to reduce their speed if there is no oncoming vehicle approaching
  • Motor vehicles without priority may race to the chicane before an oncoming vehicle approaches, or swerve dangerously around the chicane
  • Where traffic flows are low or tidal there is very little speed reducing benefit as drivers rarely have to give way
  • Where there is little need to give way drivers become used to not stopping and may fail to stop when necessary
  • May cause long delays if there is increased vehicle traffic
  • Buses without priority will find it more difficult to find a gap in vehicle traffic and drive around chicanes
  • Some traffic is likely to transfer onto alternative routes, potentially causing a problem somewhere else
  • Drivers may try to pass a cyclist through the narrowing which could cause a collision
  • Can cause vehicle noise as vehicles stop and start
  • Stop-start movements may increase vehicle exhaust emissions
  • Managing water drainage could be complex and costly

Considerations

  • May cause traffic to divert to other routes
  • Priority narrowings could create motor vehicle noise which is heard in residences nearby, as many vehicles will be stopping and starting.
  • May also have an adverse effect on air quality
  • Good visibility to the feature and beyond is needed or drivers may approach too fast and be unable to stop in time
  • Priority narrowings are normally used in residential areas
  • Probably not appropriate for local distributor roads

Cost

Equipment £3,000 - £6,500
Works £1,500 - £4,000
Road Safety Audit £1,500
Traffic Regulation Order £1,000
Total£6,000 - £12,000

Costs vary depending on location, condition of existing road surface, drainage and size of the feature.


Change Lane Markings

This section explains alternative use of road markings. These measures reduce the feeling of space drivers have, which may help to reduce their speeds.

One technique is reducing the width of the lane for car drivers by adding an additional line inwards from the curb, so both lanes of drivers are moved towards the centre of the road. The space between the line and the curb is hatched with white lines. This technique is called ‘peripheral hatching’. Another technique on a two way street is removing the centre line, which is simply removing the white dashed line in the middle of the road.

Effectiveness

Peripheral Hatching

By visually reducing the lane width drivers need to focus more on their road position which in turn reduces speeds.

Removing the Centre Line

If the centre line is removed, this removes driver’s feelings of ‘designated space’ for them to drive in. They may expect other road users to enter their path, or make an unexpected manoeuvre. This is more likely to cause drivers to slow down as a precaution.

Reducing motor vehicle speeds increases safety because:

  • The vehicle has travelled a shorter distance by the time a driver can react to a hazard
  • Braking distance is reduced, so the vehicle can stop more quickly before a hazard
  • Higher speed crashes tend to result in higher severity injuries
Straight road with no centre line marking

Road with no centre line

Advantages Disadvantages
  • Does not introduce discomfort to motor vehicle drivers
  • Relatively cheap
  • Does not reduce accessibility for emergency vehicles or buses
  • Peripheral hatching could be ignored by some motor vehicles drivers, who might still drive in this space
  • Removing the centre line may cause some confusion to motor vehicle drivers
  • Can become a maintenance liability if the lining requires refreshing regularly

Considerations

  • The removal of the centre line can damage the road surface if it is already in poor condition
  • Peripheral hatching can hold a build of debris due to it not being trafficked.
  • Centre lines should not be removed when traffic speeds are particularly excessive
  • Peripheral hatching can only be used on relatively wide roads (e.g. 12 meters)
  • Centre line removal should not happen near one-way streets to avoid confusion
  • Requires a Road Safety Audit

Cost

Equipment £500 - £1,500
Works £500 - £2,000
Road Safety Audit £1,500
Total£2,500 - £5,000
Costs vary depending on location, condition of existing road surface and amount of lining/removal required

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