Surviving car crashes

Updated: Feb 24 2002, 05:30am hrs
Though crash-proof cars may be a distant dream, driving is becoming comparatively safer and less taxing on both the man and the machine with each passing day. Some new technologies, which include anti-lock braking systems (ABS), airbags, traction control and stability programmes have been available in Europe and America since the 1980s, now these are making their presence felt in India, too.

Seat belts
Seat belts were invented 40 years ago and continue to play the single most crucial role in protecting human life. The device was invented by Nils Bohlin and patented by Volvo in 1959. In the beginning, the concept of using a fabric belt system to hold vehicle occupants in place during an accident was viewed with skepticism by both the automobile industry and the general public.

Initially, the belts were provided only in Volvos home market cars, but by 1963 all Volvos came equipped with front passenger, three-point belts. While laws requiring the addition of safety belts in vehicle production first appeared in the 1960s, it is only during the last 15 years that laws requiring the use of seat belts have been enacted all over the world. In India, the first state to introduce mandatory seat belts was Punjab over a year ago and now they have become compulsory for front seat occupants in passenger cars in Delhi also.

Although airbags have taken some heat in recent years, it continues to play a vital role in protecting drivers. If used properly, it offers the best second line of defence (the first being the traditional seat belt) against serious injury and even death. Airbags came into picture in the 60s and the 70s. Airbags get deployed as a result of a simple but powerful chemical reaction.

When a car is involved in a frontal collision with an object while traveling at over 30 km per hour, a motion sensor sends an electrical shock to a small capsule of sodium azide powder, which instantly turns into inert nitrogen gas. This gas fills a lightweight nylon bag, which pops out of a latched panel and covers your head and upper torso. All this happens very quickly. It takes about 30 milliseconds for an airbag to deploy, while it takes 100 milliseconds to blink. Airbags start deflating within a second of their release. Most air bags are triggered electrically by a signal from the vehicles crash sensors and/or ABS control module.

Says Gautam Sen, editor-in-chief, Automotor and Sports: In order to allow the air bag to deploy safely, front seat passengers should avoid leaning or reaching forward and should remain seated against the seat back, with a minimal slack in the belt to minimise forward movement in a crash. It is necessary to wear a seat belt in cars, which have airbags or else the force of airbag deployment may cause injury.

Anti-lock braking systems
Laying the groundwork for stability control in the mid-80s, Bosch brought the antilock braking system (ABS) into market through the Mercedes and the BMW. Anti-lock brakes are controlled by a computer chip, which senses when a wheel is locked up, or is about to lock up. When this occurs, the computer tells brake sensors to apply intermittent brake pressure, which prevents the wheel from locking. Essentially, the computer and brake sensors do exactly the same thing drivers would do if they pumped the brakes. The only difference is that the computer-controlled sensors can pump the brakes much quicker than a human being can.

Traction control
After Bosch perfected ABS, the company moved on to second building blocktraction control. Sometimes referred to as ASR traction control (ASR stands for Acceleration Slip Regulation and typically refers to systems appearing in German cars), the technology works like the ABS, but at the opposite end of the performance spectrum. Whereas ABS focusses on eliminating lock-up in braking situations, traction control regulates wheelspin during acceleration. In other words, when speeding from a standing stop or while in motion, a driver may give too much accelerator input, causing the wheels to spin freely. In such cases, traction control monitors wheel speed, cuts engine power or even applies the brakes to optimise contact between the tyres and the road surface.

For instance, a wet or icy road surface will significantly reduce the friction (traction) between your tyres and the pavement, which can result in serious consequences. Traction control deals specifically with lateral (front-to-back) loss of friction during acceleration.

According to Mr Sen: TCS comes handy under slippery conditions. In fact, it is of great help in Europe, where people drive at 120-130 km/h on highways even under rainy conditions.

Stability control
The third building block in modern braking systems, stability control incorporates everything ABS and traction control do plus a yaw-sensing feature that works to increase traction during potential side-skidding situations. (Yaw can be described as the movement of an object turning on its vertical axis). In other words, whereas both ABS and traction control work on the longitudinal (front-to-back) axis of the vehicle, stability control operates on the lateral (side-to-side) axis. Boschs Electronic Stability Program (ESP), the first such system in the market, began appearing in 1995 Mercedes-Benz S-Class sedans. It has since become a popular feature of many upscale vehicles. In addition to discrete electrical components, ceramic sensors and solenoid valves, stability control systems typically utilise wheel-speed sensors, steering-angle sensors and a hydraulic modulator. The key component is, however, something called a rotational speed sensor (also known as a yaw-rate sensor). The yaw-rate sensor determines how far off axis a car is tilting in a turn. This information is then fed into a microcomputer that correlates the data with wheel speed, steering angle and accelerator position and, if the system senses too much yaw, the appropriate braking force is applied.

Here, the system does most of the thinking for you. Depending on the particular driving situation, the system may activate an individual wheel brake or any combination of the four, as well as control the throttle, until the vehicle is once again stable. Second, the system is fully independent of the drivers actions. Even if the car is free-rolling (no acceleration or braking input from the driver), the stability control system will kick in and perform its duty. All you need to do is steer. As with many high-tech advances, the original designs made debut in German vehicles, typically Mercedes S-Class and BMW 7 Series sedans.

Safety devices in India
Today many new Indian vehicles are coming with all these devices. According to Bipin Datar of Skoda Auto India: Airbags are standard in driver and passenger side in Skoda. We dont compromise on safety. ABS is standard in the Petrol Octavia and is a valuable tool to prevent lateral skidding on slippery surfaces in case of emergency braking. We also have an automatic fuel cut of switch that is activated so as to protect fire hazards and explosions. The electrical circuit also cuts off and prevents the short circuit.

Safety is high on the priority list of most manufacturers, especially in the D-segment (above Rs 12 lakh). Says Ananda Mohan Gupta, general manager, Marketing of Honda Siel: Apart from the standard features existing in other the C (Rs 4.5 lakh-Rs 12 lakh) and the D segment cars, the Accord has driver and passenger side airbags and ABS as standard across all variants. Because of a strong emphasis on safety at Honda, these are not add-on options. Active safety features, which prevent accidents (as opposed to passive safety features, which prevent injury during accidents) are a hallmark of Honda.

Sums up Bhuvana Ramalingam, manager, Public Affairs, Ford Motor India Limited: Safety features are extremely important for any road condition. There might be a mistaken perception that such features are necessary only for roads that allow for high speeds. Accidents occur when vehicles are driving at low speeds or even while standing. Therefore, safety features are absolutely necessary for all vehicles and for all kinds of road conditions. There was some controversy regarding the safety of air bags earlier. They have now evolved to offer a higher safety level. In the Mondeo, for instance, airbags are controlled by an intelligent protection system (IPS), which releases airbags in stages depending upon the level of impact. But it is true that airbags will not be effective if the seat belt is not used. Nevertheless, safety features such as impact beams, ABS, and collapsible steering would be very useful.