Ergonomic Design of Vehicle to Improve Highway Safety
Er. C. S. Verma (CHHAVI SHANKER VERMA)
F.I.E., Ex-General Manager, National Highway Authority of India (NHAI)
Highway traffic accidents are the leading cause of deaths in the world, especially for the age group of 15 to 49 years, where it may be termed as the principal cause of death in this age group. During the year ending 2021, in India, the total fatalities due to road accidents were near about 154,000 in numbers, and it is on an increasing trend, which is a serious concern of policymakers in our governments.
In this very year, Indian highways witnessed:
- 30.6% of accidents resulting in grievous injuries.
- 29% of accidents causing minor injuries.
It has statistically been observed that pedestrian, cyclist, and motorcyclist deaths on highways account for more than 68% of total fatalities. A study of traffic accident patterns in Chhattisgarh State shows that:
- Deaths of more than 40% of motorcyclists occur due to crashes with either trucks or tractors.
- At least 75% of pedestrian and cyclist deaths are caused by crashes involving either trucks, tractors, or erroneously driven motorcycles.
- Trucks and buses are responsible for more than 70% of fatal crashes.
It is pertinent to mention here that, in most cases, accidents happen due to non-adherence to safety laws/parameters by road users, which can be termed human error or human factor.
There are three major factors contributing to road accidents:
- Human Factors – The primary cause, including reckless driving, fatigue, and inattention.
- Road Environment Factors – Poor road conditions, inadequate signage, and infrastructure issues.
- Vehicle Factors – An increasing number of vehicles, growing vehicle sizes, and a changing driver demographic with more elderly drivers.
A survey conducted in Latin American countries found that more than 8-10% of accidents occur due to vehicle factors alone.
Several active safety systems are already available, which:
- Alert drivers with forward collision warning signals.
- Assist drivers when a vehicle approaches a blind spot during lane-changing maneuvers.
To enable drivers to comprehend these warning signals effectively and enhance safety, a thoughtful driver-vehicle interface system design is desirable. The vehicles are dependent on the human being for its control & operation, meaning thereby that a system comprising the vehicle and the human is formed during the vehicle driving. Therefore, to achieve qualitative as well as quantitative performance during vehicle driving on the road, both elements of the system should work in harmony. To meet this, the design of the vehicle should conform to vehicle ergonomic design criteria. The compliance of these criteria for ergonomic design of the vehicle is important to avoid serious and fatal accidents on the road and the loss of human lives.
The basic aim of ergonomics is to create a proper driver-vehicle interface design so that the designed equipment will facilitate the proper and timely interaction between the driver and the vehicle, resulting in the safety of the driver, occupants, and other road users. The parameters which need to be taken care of for vehicle design are speed of the vehicle, vehicle capacity, and its size. The vehicle should be designed for achieving a close link between the biological and psychological behavior of the driver and the designed physicality of the vehicle so that they can perform perfectly even in the most adverse conditions.
The term Ergonomics is a combination of two Greek words: Ergo and Nomous. The word ergonomics means the natural law of doing work. Ergonomics ensures a cohesive relation between people, their actions, their interaction with the object, and the environment. The ergonomic design of a vehicle consists of anthropotechnic design, interface design, and the design of the driver’s working environment.
The essential parameters for ensuring that the driver may feel comfortable in adjusting posture on his driving seat after entering the vehicle are the provision of proper back support, hip lift, proper eye level, proper back lean, and proper headrest position. These can be termed as elements of driver ergonomics.
The International Organization of Motor Vehicle Manufacturers (OICA) is the official designated representative at the United Nations for almost all the vehicle manufacturers in the world. OICA says that vehicle requirements vary by region and so the requirements most suitable to a given territory, depending upon the people’s needs in that area, have to be studied first. After this, the vehicle requirements and its design should be based on the Global Technical Regulations under the UN 1988 agreement.
The safety of a vehicle and its occupants is of prime importance, and care should be taken to comply with various norms of safety such as:
- Active safety
- Driving safety
- Safety during operation (inclusive of perceptibility safety)
- Passive safety
- Exterior & interior safety
The structural integrity of the vehicle body and its deformation behavior during side, rear, or frontal impact should be studied.
Active Safety Systems
Active safety systems are systems that help the driver in controlling the vehicle in case of an accident and are automated for countering human error. This system is a preventive approach that helps on the road to avoid accidents. Examples include:
- Anti-lock Braking System (ABS)
- Electronic Stability Control (ESC)
- Traction Control System (TCS)
In the absence of ABS, the vehicle skids in case of emergency braking situations, and the wheel locks, causing the loss of driving stability.
Passive Safety Systems
In the case of an unavoidable crash, the passive safety system helps to protect the driver and occupants from injuries. The most glaring example of a passive safety system is airbags, which helps protect the occupants from serious or grievous injuries. Other features of passive safety are:
- Seat belts
- Roll-over bars
Smart airbags, crash sensor systems, breakaway engines, rollover protection bars, and engine immobilizers are key safety features of a smart and safe Light Motor Vehicle (LMV). To enhance chassis control during motion, technologies such as anti-lock braking systems (ABS), traction control systems, electronic damping control, and power-assisted steering are employed.
The efficiency of the braking system depends on the available traction at the tire-road interface. Braking performance varies significantly between slippery, wet roads and dry surfaces. Additionally, braking behavior differs between laden and unladen vehicles, as well as between straight-line braking and braking on curves. Speed sensors and brake force modulators are integral components of electronic brake force distribution systems.
Key design factors that must be considered include wheelbase, vehicle mass, center of gravity (both laden and unladen), maximum allowable speed, tire and rim configuration, and braking standards. It is crucial to highlight that brakes, steering, and suspension systems serve as crash avoidance mechanisms, particularly in response to potholes and surface irregularities on the road.
Various UN regulations establish global vehicle safety standards. UN Regulations 94 and 95 define frontal and side impact protection standards, ensuring vehicle crashworthiness in crash tests. UN Regulation 140 outlines electronic stability control (ESC) requirements, which include ABS. For two-wheelers, such as motorcycles, UN Regulation 78 mandates anti-lock braking systems to help control skidding. Additionally, UN Regulation 127 focuses on reducing severe injuries to pedestrians.
The installation of ABS in both motorcycles and cars significantly improves steering control, prevents skidding, reduces vehicle rotation, and shortens stopping distances. ESC further enhances vehicle control by individually monitoring wheel speeds and applying brakes as needed. A survey conducted in Latin American countries found that ABS and ESC contributed to reducing accident-related fatalities by approximately 9% and 20%, respectively.
Motorcycles equipped with ABS offer enhanced rider safety, substantially lowering fatality rates in accidents. Likewise, the adoption of ABS in four-wheelers plays a crucial role in controlling pedestrian death rates.
To minimize the adverse effects of side impacts, side airbags are highly desirable. Additionally, side structures can be reinforced using energy-absorbing padding cushions.
A critical aspect of vehicle safety is evaluating whether a vehicle’s design complies with international safety standards. Crash test methods are employed to assess a vehicle’s safety performance, particularly in terms of occupant protection. Ensuring vehicle crashworthiness is essential to minimizing the risk of severe or fatal injuries to occupants.
Globally, organizations such as the U.S. National Highway Traffic Safety Administration (NHTSA), the Economic Commission for Europe, and regulatory bodies in China have developed their own vehicle safety standards. In India, the government has introduced the Bharat NCAP, a new car assessment program that assigns star ratings to evaluate vehicle safety. This program includes a 16-point front impact test and a 16-point side impact test. However, the impact testing speeds under Bharat NCAP are lower than those in the Global NCAP.
Despite these efforts, safety regulations and rating systems across different regions lack uniformity. Research indicates that existing U.S. vehicle safety standards and rating systems are inadequate in protecting individuals outside the vehicle, particularly in the context of rapidly increasing multimodal traffic on roads.
“Due to the ever-increasing size and weight of vehicles, pedestrian and cyclist fatalities have risen to alarming levels. In 2023, the National Highway Traffic Safety Administration (NHTSA) proposed regulations requiring Cars, SUVs, and light-duty trucks to be equipped with Automatic Emergency Braking (AEB) to help reduce pedestrian fatalities.”
References:
- Road Accidents in India – TRW of MoRT&H
- Road Safety in India: Status Report 2021 – TRIP Centre, IIT Delhi
- Effects of Vehicle Safety Design on Road Traffic Deaths in the Latin American Region: A Modelling Study – Kavi Bhalla
- Ergonomics in the Automotive Design Process – Vivek D. Bhise
- An Introduction to Modern Vehicle Design – Julian Happian Smith
- Vehicle Design – National Association of City Transportation Officials (NACTO)
