Delineation

Centre and edge delineation treatments help drivers judge their position on the road, and provide advice about conditions ahead. Delineation treatments are particularly helpful where visibility can become poor (for example, due to rain, fog or darkness) and on sharp bends.

There are many delineation treatments available, and these should be used in a consistent manner along a route or road network. Example delineation treatments include:

Line marking

Painted line marking is relatively cheap. Centrelines can be used to discourage overtaking or accidental ‘drifting' from the lane. Edge lines help drivers judge the alignment of the road ahead and can reduce run-off-road crashes. Line marking is also effective at reducing shoulder damage, and therefore in reducing maintenance costs. Rumble strips or profiled line marking applied as an edgeline or centreline can be effective in reducing run-off-the-road and head-on crashes, particularly crashes related to driver fatigue.

Retroreflective Pavement Markers (RRPMs)

Retro-reflective pavement markers or road studs ('cats eyes') are usually used in conjunction with painted line marking to warn drivers of changes in alignment in the road ahead. RRPM's are particularly helpful in darkness or during wet weather when line marking becomes difficult to see.

Guide posts

Guide posts assist the road user by indicating the alignment of the road ahead, especially at horizontal and vertical curves. Guide posts are usually about one metre high and set about one metre from the edge of the road. They can be equipped with reflectors, or painted with reflective paint, and so are especially useful at night. They should not constitute a roadside hazard, and so should be constructed of lightweight, frangible, durable material. Guide posts may be necessary in some locations to show a road route in heavy snow.

Chevron alignment markers (CAMs)

CAMs or ‘chevrons' can be installed along the outside of a bend to provide drivers with a better view of the bend as they approach it, and to assist them in positioning the vehicle during the bend.

Warning signs and advisory speed signs

Warning signs inform drivers of the nature of a hazard they are approaching. Advisory signs, including advisory speed signs, tell drivers how to navigate the hazard safely. For example, hazardous bend signs placed on the approach to the bend can inform the driver of how the road alignment changes. Hazardous bend signs can be mounted above an advisory speed limit sign which states a safe speed for the bend.

  • Road markings are among the most cost-effective treatments to make roads safer.
  • Delineation improvements have been shown to reduce head-on and run-off road crashes.
  • Helps drivers to maintain a safe and consistent lateral vehicle position within the lane.
  • Reduction in nighttime and low-visibility crashes.
  • Reduction in pavement deterioration due to vehicles driving onto the shoulder.
  • In many countries linemarking is ignored (and physical barriers to crossing the centre line are needed).
  • Poorly designed or located delineators can add to crash risk.
  • Too many signs can confuse drivers.
  • Road studs require a good quality road surface.
  • Delineation needs to be consistent throughout an entire country.
  • The retro-reflectivity of lines and signs is an important consideration for road use at night and in the wet.

Benefits

  • Road markings are among the most cost-effective treatments to make roads safer.
  • Delineation improvements have been shown to reduce head-on and run-off road crashes.
  • Helps drivers to maintain a safe and consistent lateral vehicle position within the lane.
  • Reduction in nighttime and low-visibility crashes.
  • Reduction in pavement deterioration due to vehicles driving onto the shoulder.

Implementation issues

  • In many countries linemarking is ignored (and physical barriers to crossing the centre line are needed).
  • Poorly designed or located delineators can add to crash risk.
  • Too many signs can confuse drivers.
  • Road studs require a good quality road surface.
  • Delineation needs to be consistent throughout an entire country.
  • The retro-reflectivity of lines and signs is an important consideration for road use at night and in the wet.

Did you know?

Median barriers physically separate opposing traffic streams and help prevent head on crashes.

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Treatment Summary

Costs
Low
Treatment life
1 year - 5 years
Effectiveness
10-25%

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