--- title: "Critical characteristics of the driver" subject: "Transportation Engineering II" chapter: 1 key: "semester_7/transportation_engineering_ii:driver-characteristics" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/driver-characteristics site: BCT Engineering --- # Critical characteristics of the driver Transportation Engineering II · Chapter 1: Traffic Engineering - Asked in: 2079 Bhadra, 8 marks; 2078 Bhadra, 8 marks; 2076 Asoj, 8 marks (asked 3 times) - 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/driver-characteristics - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-1 ## Question Describe the critical physical, mental and psychological characteristics of driver that affect his/her traffic performance. ## Short answer Critical physical traits are vision, hearing, reaction ability, age/health and fatigue/alcohol/drugs; mental traits include intelligence, training, attention, memory and the PIEV reaction process; psychological traits include emotion, attitude, anxiety and driving experience. Design uses a conservative 2.5 s perception-reaction time and vision-based sign sizes. ## Answer Driver characteristics are the personal attributes that decide how a driver senses, decides and acts in traffic. The critical ones are physical, mental and psychological. #### Physical characteristics - **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. #### Mental characteristics - **Intelligence and judgement:** the ability to judge speed, distance, gaps and the intentions of other road users. - **Knowledge and training:** familiarity with traffic rules, signs and the route; drivers unfamiliar with a route hesitate and make errors. - **Attention and concentration:** a driver can attend to only a limited amount of information at a time; distractions (mobile phone, passengers) reduce attention. - **Memory and learning:** help in recognising signs and routes and in forming habits. - **Perception-reaction process (PIEV):** perception, intellection, emotion and volition, which together determine the total reaction time. #### Psychological characteristics - **Emotional state and temperament:** anger, stress, worry or elation lead to aggressive driving, overtaking in unsafe places and over-speeding. - **Attitude and behaviour:** attitude towards rules, other users and risk; over-confident or risk-taking drivers have more crashes. - **Anxiety and fear:** a nervous driver may brake suddenly or hesitate at intersections. - **Social habits:** lane discipline, courtesy, and the tendency to follow the crowd. - **Driving habits and experience:** young drivers take more risks; experienced drivers anticipate hazards better. - **Response to stimuli:** drivers react quickly to expected events but slowly to unexpected ones (for example a stationary vehicle on a bend). #### Design implication Because drivers vary, design values are taken for an average or conservative driver: a perception-reaction time of 2.5 s for sight distance (IRC:66, IRC:SP:23; Nepal Road Standard 2070), sign letter sizes matched to visual acuity, and lighting and markings to help night vision. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which set correctly names the critical driver characteristics that affect traffic performance? A. Physical, mental and psychological B. Physical, economic and legal C. Mechanical, mental and social D. Visual, financial and psychological Answer: A. The answer groups driver characteristics into physical, mental and psychological ones. (Key point: Three groups of driver characteristics) 2. What does the PIEV process describe? A. The four types of vision a driver has B. Perception, intellection, emotion and volition that together make up total reaction time C. The four stages of vehicle braking D. Pedestrian, intersection, emergency and vehicle factors Answer: B. PIEV stands for perception, intellection, emotion and volition, which together determine reaction time. (Key point: PIEV process) 3. What is the main effect of fatigue, alcohol and drugs on a driver? A. They narrow the road but speed up response B. They only affect hearing C. They lengthen reaction time, impair judgement and cause drowsiness D. They improve concentration for short periods Answer: C. These conditions lengthen reaction time and impair judgement, so driving under their influence is prohibited. (Key point: Effect of fatigue, alcohol and drugs) 4. Why is a perception-reaction time of 2.5 s used for sight distance design? A. Every driver reacts in exactly 2.5 s B. Drivers vary, so a conservative value is used rather than the fastest driver's value C. It is the time a vehicle takes to stop D. It equals the time for glare recovery Answer: B. Because drivers differ, design adopts an average or conservative value (2.5 s) to suit most drivers. (Key point: Design reaction time) ## 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 - [Human-vehicle-environment system; driver characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Ahve-system-driver-physical-characteristics) — Transportation Engineering II, chapter 1 - [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 - [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 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 - [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 - [Critical resistance, critical speed and shunt generator characteristics](https://www.bctengineer.com/question.md?key=semester_4%2Felectrical_machines_i%3Acritical-resistance-speed-shunt-characteristics) — Electrical Machines I, chapter 3 - [Physical characteristics; decomposition of wastewater](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Aphysical-characteristics-decomposition) — Sanitary Engineering, chapter 5 - [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 - [UTP characteristics and performance](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Autp-characteristics) — Data Communication, chapter 4