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Night visibility, road marking, traffic islands

Short answer

Night visibility depends on headlight intensity, glare, pavement contrast, weather, and retro‑reflective signs/markings. Road markings include centre/lane/edge lines, stop lines, zebra crossings, and kerb markings. Traffic islands: channelising, dividing (median), pedestrian refuge, rotary central, and splitter islands, used to guide and separate traffic safely.

What are the factors affecting Night Visibility? What are the different types of road marking and traffic island used to regulate and control traffic flow? Explain.

Factors affecting night visibility

  • Headlight intensity, beam type and alignment; glare from opposing lights and glare recovery time.
  • Street lighting level and uniformity.
  • Contrast and reflectance of the object and the pavement (a wet or dark pavement reflects little light).
  • Vehicle speed, the age and eyesight of the driver, weather (fog, rain) and a dirty windscreen.
  • Presence of retro-reflective signs, markings and delineators.

Road markings (IRC:35)

  • Pavement markings: centre line, lane lines, edge lines, no-overtaking (barrier) lines, stop and give-way lines, zebra crossings, arrows and words, hatching.
  • Kerb markings: black/yellow bands for no-parking or no-stopping.
  • Object markers: black-white or yellow-black bands on piers, abutments and poles.
  • Parking bay markings.

Colours: white for lane and edge lines, yellow for no-overtaking and kerb restrictions. Thermoplastic paint with glass beads is used for night visibility.

Traffic islands

  1. Channelising islands: triangular or teardrop islands that guide vehicles into definite paths and prevent wrong movements, usually at the junction of a minor road with a major road.
  2. Dividing (separating) islands / medians: separate opposing traffic flows on the approaches of a junction or on a divided road and reduce head-on conflicts.
  3. Pedestrian refuge islands: a safe place in the middle of the carriageway where pedestrians wait while crossing; at least 1.5 m wide (preferably 2.0 m) and at least as long as the crosswalk is wide.
  4. Rotary (central) island: the central island of a roundabout around which vehicles circulate.
  5. Splitter islands: at the entry of a rotary on each approach, to keep traffic on its own side and reduce speed.
  6. Traffic control islands: for signs, signals and luminaires.
  7. Loading and bus-stop islands.

Islands are made of kerbed concrete or masonry with a mountable or barrier kerb, painted with reflective markings; the nose is offset about 0.5 m from the edge of the carriageway (IRC:SP:41).

✓ Answer checked by Claude Opus 5.5 (high effort)

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