Public Realm Information & Advice Network
know how


9 Traffic calming & parking
    › 9.1 Natural traffic calming
    › 9.2 Parking techniques
    › 9.3 Sight Lines




9.1 Natural traffic calming
The principle of traffic calming is to require drivers to drive slowly and respect other road users, notably pedestrians. This can be done by legally enforced regulation often involving signs and lines. Natural traffic calming uses physical restrictions to reduce forward visibility or cause drivers to reduce speed in order to turn sharply or negotiate a stretch of narrow road.  Parked cars at right angles to the road, or trees in the road all help reduce speed and can be incorporated seamlessly into the surrounding built form to appear to be a natural part of the street scene.



9.2 Parking techniques: Yellow lines

Width of yellow lines
Yellow lines may be 100 mm wide (4 inches) or 50 mm wide (2 inches). yellow_lines

Even though chapter 5 of the Traffic Signs Manual states that 50 mm wide lines may be used in environmentally sensitive areas, this is only partially true. The Manual is advisory and it is for the local Traffic Authority to decide which width is appropriate.

Under the statutory Traffic Signs Regulations and General Directions (TSRGD), 50 mm wide lines may be used anywhere.Therefore the Traffic Authority can lawfully apply the narrower 50 mm yellow lines, rather than the 100 mm wide lines, where ever it wishes.

Precise colour of yellow lines
A paler yellow, known as primrose, is less garish than the normal yellow colour. Although the Traffic Sign Manual recommends its use only in environmentally sensitive areas, it is acceptable as yellow under the TSRGD. 

The Traffic Authority can lawfully apply the subtle primrose colour rather than the more vivid yellow, where ever it wishes.


Alternative to yellow lines
Where a restrictive parking zone is designated, yellow lines may be omitted and replaced with signs. In these zones parking is only permitted where bays are marked.

9.3 Sight Lines

Sight lines download

Sight lines are the clear lines of sight a driver has of other vehicles at a road junction. The theory is that the further a driver can see the more time a driver has to avoid an accident. Long sight lines are applied to new junctions to make them safe.

sight lines

Many historic villages and towns have charming narrow roads with tight corners and bad sight lines. Are they really unsafe?

The Department for Transport document Manual for Streets explains that each local authority should decide for itself what is safe, depending on the evidence and local circumstances.

PRIAN has studied various junctions in narrow historic streets. We have observed that drivers consistantly drive with more care where sight lines are reduced. Historic public realm may be retained and new junctions created with the knowledge that tight corners can be safe for pedestrians and drivers.

Sight Lines



PRIAN is a not for profit organisation supporting individuals, professional bodies and government in improving the public realm. All material published on this website is copyright PRIAN unless otherwise stated. Copyright © PRIAN 2007     Contact us