--- title: "Human-vehicle-environment system; driver characteristics" subject: "Transportation Engineering II" chapter: 1 key: "semester_7/transportation_engineering_ii:hve-system-driver-physical-characteristics" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/hve-system-driver-physical-characteristics site: BCT Engineering --- # Human-vehicle-environment system; driver characteristics Transportation Engineering II · Chapter 1: Traffic Engineering - Asked in: 2080 Bhadra, 8 marks - Video: [Traffic Characteristics - Traffic Engineering - GATE Transportation Engineering](https://www.youtube.com/watch?v=gvgwYeXyn_U) — Ekeeda GATE & ESE - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/hve-system-driver-physical-characteristics - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-1 ## Question Explain human-vehicle-environment system. Discuss physical characteristics of driver that affect traffic performance. ## Short answer HVE system couples human road user, vehicle, and road environment; mismatch causes crashes. Driver physical characteristics affecting traffic are vision (acuity, field, colour, glare, depth), hearing, reaction ability, age/health, and fatigue/alcohol/drugs, which impair perception and response. ## Answer #### Human-vehicle-environment (HVE) system The traffic stream is the combined behaviour of three interacting elements: the **Human (road user)**, the **Vehicle** and the **Environment (road and surroundings)**. Safe and efficient flow needs all three to match. ```text +--------------+ | HUMAN | driver, pedestrian, | (perception, | cyclist, passenger | reaction) | +------+-------+ controls| ^ feedback v | +------+----+--+ +--------------------+ | VEHICLE |<---->| ENVIRONMENT | | size, power, | | road geometry, | | brakes, load | | surface, signs, | +--------------+ | weather, lighting | +--------------------+ ``` - **Human:** receives information (mostly visual), decides and acts (steering, braking). Errors in perception, judgement or reaction are the main cause of crashes (about 80-90 percent involve human error). - **Vehicle:** its dimensions, weight, power, braking and visibility set the road width, gradient, curve radius and pavement strength required. - **Environment:** road geometry, surface friction, traffic control devices, lighting, weather and adjacent land use affect how the driver sees and responds. A mismatch in any one (for example a fast vehicle, a sharp curve and a wet surface) causes crashes, so the design must fit the "design driver" and "design vehicle" to the road. #### Physical characteristics of the driver that affect traffic performance - **Vision:** acuity (normal acuity is 6/6), the field of vision (clear vision within a cone of about 3-5 degrees, fairly clear up to about 10-12 degrees, peripheral vision up to about 120-180 degrees), colour perception (red/green colour blindness is critical for signals), glare sensitivity, glare recovery and depth perception. Speed narrows the field of vision (at 100 km/h it is only about 40 degrees). - **Hearing:** detecting horns and sirens; deafness is partly compensated by vision, but it reduces awareness of emergency vehicles. - **Reaction ability:** muscle coordination, strength and speed of hand/foot response; fatigue, age and disability reduce it. - **Age and health:** reactions slow and vision/hearing fade in old age; illness, epilepsy and heart conditions are hazards. - **Fatigue, alcohol and drugs:** these lengthen reaction time, impair judgement and cause drowsiness; Nepal's Motor Vehicles and Transport Management Act 2049 prohibits driving under the influence. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which three elements make up the human-vehicle-environment system? A. Driver, road and traffic police B. Human (road user), vehicle and environment (road and surroundings) C. Vehicle, fuel and pavement D. Pedestrian, signal and speed Answer: B. The traffic stream is the combined behaviour of the human, the vehicle and the environment, which must match for safe flow. (Key point: Elements of HVE system) 2. Why is the human element usually treated as the most critical in the HVE system? A. Humans never perceive visual information B. About 80-90 percent of crashes involve human error in perception, judgement or reaction C. Vehicles have no effect on road design D. Human error only occurs at night Answer: B. Errors in perception, judgement or reaction are the main cause of crashes. (Key point: Role of human error) 3. What does the HVE concept imply for design? A. Design only for the average vehicle B. Fit the design driver and design vehicle to the road, since a mismatch of any element causes crashes C. Ignore the environment in design D. Only geometric design matters Answer: B. A mismatch such as fast vehicle, sharp curve and wet surface causes crashes, so design must fit the design driver and vehicle. (Key point: Mismatch causes crashes) 4. How does vehicle speed affect a driver's field of vision? A. It widens it B. It narrows it, e.g. to about 40 degrees at 100 km/h C. It has no effect D. It only affects colour perception Answer: B. As speed rises the field of vision narrows; at 100 km/h only about 40 degrees remains. (Key point: Speed and field of vision) 5. How do fatigue, alcohol and drugs affect driving performance? A. They shorten reaction time B. They lengthen reaction time and impair judgement C. They improve glare recovery D. They only affect hearing Answer: B. They lengthen reaction time, impair judgement and cause drowsiness, hence driving under the influence is prohibited. (Key point: Fatigue, alcohol and drugs) ## Related in Transportation Engineering II - [Driver vision characteristics affecting traffic](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Adriver-vision-characteristics) — Transportation Engineering II, chapter 1 - [Critical characteristics of the driver](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Adriver-characteristics) — Transportation Engineering II, chapter 1, asked 3× - [Vehicular characteristics influencing traffic performance](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Avehicular-characteristics-traffic-performance) — Transportation Engineering II, chapter 1 - [Traffic engineering; road user characteristics and HVE](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ate-definition-road-user-hve) — Transportation Engineering II, chapter 1 - [Critical road user and static vehicle characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aroad-user-static-vehicle-characteristics) — Transportation Engineering II, chapter 1 - [Traffic engineering; road users and vehicular characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ate-definition-road-users-vehicular) — Transportation Engineering II, chapter 1 ## Related in other subjects - [Human civilization, development and the environment](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Acivilization-development-environment-history) — Environment and Pollution Control, chapter 7 - [Hybrid vehicle and environment impact](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Ahybrid-vehicle) — Energy Environment and Society, chapter 5, asked 2× - [Physical and chemical characteristics of solid waste](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Asolid-waste-characteristics) — Environment and Pollution Control, chapter 5 - [Classify project; characteristics; good environment](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Aclassify-project-importance-environment) — Project Engineering, chapter 1