What are Traffic Control Devices?
Traffic control devices include all signals, signs, road markings, and other devices used with the approval of the traffic authority to regulate, warn, and guide traffic. They serve three primary functions: regulatory (enforcing laws), warning (alerting drivers to hazards), and guiding (providing directions and information).
Three Types of Traffic Signs
1. Regulatory / Mandatory Signs
Regulatory signs inform road users of traffic laws and regulations that apply at a specific location. Shape: Circular (disc) — except STOP (octagonal) and GIVE WAY (equilateral triangle with apex downward). Colours: Red border, white background, black character. Disc diameter: 600–1200 mm. Octagon height: 750–1200 mm. Examples: Speed limit, No U-turn, No parking, Compulsory keep left, Right turn prohibited.
2. Warning / Cautionary / Danger Signs
Warning signs alert drivers to potentially hazardous conditions ahead. Shape: Equilateral triangle with apex upward. Colours: Red border, white background, black character/symbol. Same size range as regulatory signs. Examples: Right-hand curve, Hairpin bend, Step ascent, Narrow road ahead, Narrow bridge, Pedestrian crossing, Gap in median, Men at work, Major road ahead.
Note: “Dead slow” sign falls under the barrier category — it is a warning sign.
3. Informatory / Guide Signs
Informatory signs provide directions, distances, destinations, and other geographical or cultural information. Shape: Rectangular. Height: 5.5 m to 6.5 m above crown of pavement surface. Examples: Advance direction signs, Route markers, Hospital, Petrol pump, Eating place, Airport 20 km.
As per IRC 67-2012, signposts shall be painted in 25 cm wide bands alternating black and white for improved visibility.
Road Markings
| Marking Type | Description | Meaning |
|---|---|---|
| Broken longitudinal line | Centre line on 2 and 3-lane roads, lane marking on multi-lane | May be crossed with discretion if traffic permits |
| Solid longitudinal line | Guiding or regulating line | NOT to be crossed except for entry/exit or avoiding stationary obstruction |
| Double solid lines | Maximum restriction marking | Not to be crossed except in emergency |
| Broken + Solid combination | Mixed restriction | Solid may be crossed only if broken line is on the driver’s side |
| Stop line | Solid line perpendicular to traffic | Vehicles must not proceed beyond when required to stop |
Important: Stop lines shall only be used at locations where traffic control exists (signals, police, other devices).
Indian Highway Milestone Colour Codes
| Highway Type | Milestone Colour |
|---|---|
| National Highway | Yellow and White |
| State Highway | Green and White |
| City/District Road | Blue/Black and White |
| Rural Road | Orange and White |
Road Delineators
Road delineators are light-reflecting devices that provide visual guidance to drivers about the alignment of the road ahead, especially at night. They are classified into three types: Roadway indicators (delineate road edges to guide drivers where alignment might be confusing), Hazard markers (define obstructions like guard-rails, abutments at culverts and bridges), and Object markers (indicate hazards and obstructions within the vehicle flow path, such as channelising islands near intersections).