--- title: "Road user characteristics and their importance" subject: "Transportation Engineering II" chapter: 1 key: "semester_7/transportation_engineering_ii:road-user-characteristics-importance" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/road-user-characteristics-importance site: BCT Engineering --- # Road user characteristics and their importance Transportation Engineering II · Chapter 1: Traffic Engineering - Asked in: 2066 Bhadra, 4+2 marks - Video: [Traffic Characteristics Part-1 | Road User Characteristics | Traffic Engineering](https://www.youtube.com/watch?v=f-ukxB2qAlU) — Vaibhav Solanki - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/road-user-characteristics-importance - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-1 ## Question Describe the road user characteristics. Explain their importance in traffic engineering. ## Short answer Road users have physical (vision, hearing), mental (attention), and reaction-time (2.5 s PIEV) characteristics; pedestrian speed is 1.2 m/s, cyclists 10-25 km/h. These determine sight distance, signal timing, sign design, and safety measures. ## Answer #### Road user characteristics 1. **Physical:** vision (acuity, field of vision, colour vision, glare), hearing, strength and agility. They fix sign sizes, letter heights, lighting, sight distances and footpath gradients. 2. **Mental and psychological:** attention, judgement, emotional stability and attitude. They influence overtaking decisions, gap acceptance and compliance with signals. 3. **Reaction time (PIEV):** about 2.5 s is used for stopping sight distance, headlight sight distance and intersection sight distance (IRC:SP:23, IRC:66, Nepal Road Standard 2070). 4. **Pedestrian characteristics:** walking speed about 1.2 m/s (IRC:103 and IRC:93 use 1.2 m/s; slower, about 0.9 m/s, for children and the elderly); space needed about 0.5-0.75 m² per person; they need footpaths, crossings, refuge islands and signal time. 5. **Cyclists:** speed 10-25 km/h, need separate lanes and safe turning at intersections. 6. **Age and gender, fatigue, intoxication and disability:** these add to variation, so design uses the 85th-percentile or a conservative value (for example the 15th-percentile pedestrian speed for crossing time). 7. **Behaviour and compliance:** lane discipline, helmet and seat-belt use, jaywalking and parking habits vary by country and must be reflected in the design and enforcement plan (in Nepal mixed traffic is common). 8. **Mixed traffic:** in Nepal slow and fast vehicles share the carriageway, so wider shoulders and segregation are required. #### Importance in traffic engineering - They are the basis for design values: perception-reaction time for sight distance, walking speed for crossing and signal timing, eye height and visibility for signs and lighting. - They explain the cause of most crashes, so help to select safety measures (education, enforcement and engineering). - They help in choosing traffic control devices (size, colour, location) and the timing of signals. - They allow design for all users, including pedestrians, cyclists, children, the elderly and disabled. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What perception-reaction (PIEV) time is used for stopping sight distance design? A. 0.5 s B. 1.0 s C. 2.5 s D. 5 s Answer: C. About 2.5 s is used for sight distances. (Key point: Reaction time) 2. What walking speed is used for crossing time design? A. 1.2 m/s B. 3 m/s C. 0.2 m/s D. 5 m/s Answer: A. About 1.2 m/s, slower (about 0.9 m/s) for children and the elderly. (Key point: Pedestrian speed) 3. How does design handle variation among users? A. Use the maximum possible value B. Use a conservative value such as 85th percentile or 15th percentile pedestrian speed C. Ignore variation D. Use the average only Answer: B. A conservative percentile covers most users, for example slow pedestrians for crossing time. (Key point: Conservative design values) 4. Why are road user characteristics important in traffic engineering? A. They give design values like reaction time and walking speed, and explain causes of crashes B. They set pavement thickness C. They determine soil bearing capacity D. They only matter for tax Answer: A. They are the basis for sight distance, signal timing, sign design and safety measures. 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