Visibility of road markings

VISIBILITY OF ROAD MARKINGS

Road Marking is defined as lines, patterns, words except road signs which are applied applied or attached attached to the carriageway carriageway or kerbs or to objects objects within or adjacent adjacent to the carriageway for Controlling, Warning, Guiding and Informing the road users.

• Road markings are essential as "bare roads" lead to total confusion
• Marking helps on the road to Direct, Guide and Regulate the road user
• Road Markings include all lines patterns, words & colour applied on or attached to the road surface or kerb.
• Road Marking are used to supplement message of road signs & other devices
• ƒ Marking promote road safety & ensure smooth flow of traffic
•  Road markings
• Guides & Controls traffic on a highway 
• Delineation of Traffic path and its lateral clearance from traffic hazards facilitating safe movement ƒ 
• Channelize the pedestrians pedestrians & cyclists cyclists movement movement into safe location 
• Road markings normally include longitudinal markings, transverse markings, text and symbols etc. on the road surfaces 
• Applicable to all categories of roads even on Rural roads as well
• Traffic paints are commonly used for road markings. Other materials such as road studs, cats eyes and thermoplastic strips also find their application in road markings.
• The Colours of road markings imply specific instructions as described below:
• WHITE is used for carriageway (road) markings except those indicating restrictions 
• YELLOW markings are used to signify RESTRICTIONS. 
• WHITE or YELLOW together with BLACK are used for kerb and object marking. 
•  Different Types of Road Markings are listed below
• CENTER LINES On undivided two-way roads, the centre line separates the opposing streams of traffic and facilitates their movements.
• The centre line can be a single broken line, a single continuous solid line (barrier line) , a double solid line or a combination of solid line and broken line.
  

In order to improve visibility of road markings during poor lighting conditions or at night, different types of reflective surfaces are used.

• Diffuse reflection
• Retro reflection and
• Mirror reflection

Diffuse reflection occurs when incident light beam falls on microscopically rough surface

Retro reflection is of two types and occurs when incident light beam falls on glass beads and cube corners

Mirror reflection occurs when incident light beam falls on microscopically smooth surface. In such cases, the angle of incident light beam is equal to the angle of reflected light beam

The pattern of retro reflected light from a vehicle headlight is in a cone shaped pattern

Poor night visibility of road markings is responsible for accidents at critical spots on a road.

Road markings must be visible clearly during the day or night.

As a general requirement, drivers should be able to detect road markings at a distance equivalent to a minimum of two seconds of travel time.

The visibility distance of road markings is enhanced when the when the line thickness is wider along with a higher mark to gap ratio and higher coefficient of retro-reflective luminance. This implies that larger pavement marking widths combined with higher coefficients of retro-reflectivity are used by drivers to detect the lines according to design speed of roadway

Retro-reflectivity is accomplished in pavement-marking through the use of glass beads that are partially embedded on the  surface of the marking as binding material and also spread externally during application time.

The quality of glass beads plays an important role in retro-reflectivity of pavement marking as the glass bead returns light from a vehicle headlight to the driver

Visibility distance is adversely affected by the glare coming from on-coming vehicles, dirty head lamps or windscreen (especially during rains). Moreover, the size of a glass bead can affect retro-reflectivity especially during wet conditions.

Larger glass beads have higher retro-reflectivity in dry conditions. In wet conditions, the light is scattered due to water on the beads rendering them useless. Beads of at-least 1mm thickness effective when roads are wet.