--- title: "Traffic control devices and traffic signs" subject: "Transportation Engineering II" chapter: 1 key: "semester_7/transportation_engineering_ii:traffic-control-device-requirements-signs" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/traffic-control-device-requirements-signs site: BCT Engineering --- # Traffic control devices and traffic signs Transportation Engineering II · Chapter 1: Traffic Engineering - Asked in: 2082 Baisakh, 8 marks; 2070 Chaitra (old course), 8 marks (asked 2 times) - Video: [Traffic Engineering | Traffic Control Device | Traffic Sign](https://www.youtube.com/watch?v=9GZT1pC3GCE) — Tutorials Tips - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/traffic-control-device-requirements-signs - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-1 ## Question What are general requirements of traffic control devices? Explain the different types of traffic sign. ## Short answer Traffic control devices must fulfil a need, attract attention, convey clear meaning, command respect, allow response time, be uniform, visible at night, maintained and properly located/enforced. Signs are regulatory (circular, red border; stop octagon, give way inverted triangle), warning (equilateral triangle, red border) and informatory (rectangular, blue or green background). ## Answer #### General requirements of traffic control devices 1. **Fulfil a need:** each device must be justified by a real need based on a traffic study. 2. **Command attention:** be conspicuous (size, colour, shape, retro-reflectivity). 3. **Convey a clear and simple meaning** that can be understood at a glance. 4. **Command respect:** be used only where needed, not over-used, so that drivers obey. 5. **Give adequate time for response:** placed in advance of the hazard, with enough time to read and act. 6. **Be uniform:** the same type of device, shape and colour everywhere in the country. 7. **Be legible and visible at night** (reflectorised or illuminated). 8. **Be maintained:** clean, repainted, repaired. 9. **Be properly located and enforced** by traffic police. #### Types of traffic signs | Type | Purpose | Shape and colour | |---|---|---| | Regulatory (mandatory) | Tell the driver what to do or not do (stop, give way, no entry, speed limit, no parking) | Circular, red border, white background; STOP is an octagon, GIVE WAY an inverted triangle | | Cautionary (warning) | Warn of a hazard ahead (curve, steep descent, junction, school, narrow bridge) | Equilateral triangle, red border, white background, black symbol | | Informatory (guide) | Give directions, place names, distances, facilities (hospital, parking, fuel) | Rectangular; blue (facilities) or green (direction on highways) background, white letters | Subdivisions: informatory signs include direction signs, place identification, route markers, facility information and parking signs. **Placement:** within the cone of clear vision, 3 m lateral clearance from the edge, with a mounting height of 2.0-2.5 m above the ground; legends in a size that can be read at the speed of the road. ```text Regulatory Warning Informatory .-----. /\ +---------+ / STOP \ / \ | HOSPITAL| \ (red) / / ! \ +---------+ `-----' /______\ blue/green circle/octagon triangle rectangle ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why should traffic control devices not be over-used? A. Over-use makes them cost more to maintain only B. So that drivers keep respecting and obeying them C. Because signs must be uniform D. Because too many signs reduce night visibility only Answer: B. A device must command respect, which requires using it only where needed so that drivers obey. (Key point: Command respect) 2. Which describes a regulatory (mandatory) sign? A. Equilateral triangle with red border B. Rectangular with blue or green background C. Circular with red border and white background D. Square with yellow background Answer: C. Regulatory signs are circular with a red border and white background; STOP is an octagon. (Key point: Regulatory sign shape and colour) 3. What is the purpose and form of cautionary (warning) signs? A. They give place names; rectangular and green B. They warn of a hazard ahead; equilateral triangle, red border, black symbol C. They forbid actions such as no entry; circular D. They show facilities; blue rectangle Answer: B. Warning signs are triangles with red border and black symbol that warn of hazards like curves or junctions. (Key point: Cautionary signs) 4. Which pair of requirements is correctly explained? A. Uniform: use different shapes in each district; adequate time: place the sign at the hazard itself B. Uniform: same type, shape and colour everywhere; adequate time: place it in advance of the hazard C. Uniform: change colours yearly; adequate time: make letters smaller D. Uniform: only used on highways; adequate time: not needed in towns Answer: B. Devices should look the same everywhere and be placed in advance so the driver can read and act. (Key point: Uniformity and time for response) ## Related in Transportation Engineering II - [Traffic control devices; traffic signal advantages](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atraffic-control-devices-signal-pros-cons) — Transportation Engineering II, chapter 1 - [Night visibility, road marking, traffic islands](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Anight-visibility-road-marking-traffic-island) — Transportation Engineering II, chapter 1 ## Related in other subjects - [General requirements of functional RoR headworks](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aror-headworks-requirements-only) — Hydropower Engineering, chapter 5, asked 2× - [GSM traffic and control channels](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Agsm-traffic-control-channels) — Wireless Communication, chapter 8, asked 4× - [GSM frame structure, traffic and control channels](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Agsm-frame-traffic-control-channels) — Wireless Communication, chapter 8, asked 4× - [Control type of hydropower governor and traffic lights](https://www.bctengineer.com/question.md?key=semester_3%2Fcontrol_systems%3Ahydro-governor-traffic-type) — Control Systems, chapter 1