Why two-wheelers need ABS

Benefit estimation of anti-lock braking system for powered two-wheelers on Indian highways.

By: | Updated: March 21, 2016 12:33 PM

Motorised two-wheelers are the most common mode of transportation in India. Around one in four deaths that occurred on the roads in India in 2012 involved a motorcyclist, according to the ministry of road transport and highways.

A European Transport Safety Council analysis shows the risk of a motorcyclist having a fatal accident is 20 times greater than for a car driver travelling the same route. Thus, traffic safety for vulnerable road users like users of motorised two/three-wheelers is very important. An investigation conducted by Bosch Accident Research looked at the accident database of Road Accident Sampling System for India (RASSI). It revealed interesting facts about the Indian motorcycle accident situation, such as root causes of collisions and rider behaviour including their braking patterns during the pre-crash phase of the accident. The results were recently published at the SIAT 2015 conference.

Having a closer look at India, it can be seen that the motorcycle segment has the highest fatality rate. It is important to evaluate the root causes of accidents. Applying too little or excessive brake force when driving on Indian roads, or when taken by surprise, is one root cause. This leads to instability of the motorcycle, hence causing a fall-down or an unavoidable collision. Safety education, awareness and enforcement, i.e. the need of a helmet, is one measure for such action. Change in road infrastructure is another measure which may result in safer roads.

Let’s understand what type of brakes do riders use when faced with an emergency situation? Braking front, rear, or both? Is the braking power that is applied by the riders sufficient to avoid a fall-down prior to the collision? Today’s motorcycles can be equipped with safety systems supporting the rider in critical driving situations. A powerful and reliable braking system which provides excellent braking power even at high speeds is one example. But even the best braking system cannot prevent a rider from reacting incorrectly.

Motorcycle ABS

Due to fear of a locked wheel, riders tend to not fully apply the brakes even in emergency situations, which contributes to higher number of crashes. Anti-lock braking system (ABS) can avoid the accident or reduce collision speed significantly. As wheel-lock is prevented, optimal traction is maintained and the vehicle can remain under control.

The benefit of ABS has been confirmed by institutions including the Insurance Institute for Highway Safety in the US and Swedish Road Administration. An IIHS study showed that motorcycles above 250cc equipped with ABS are 37% less likely to be involved in fatal crashes. A study of the Swedish Road Administration came to the conclusion that 48% of all severe and fatal two-wheeler accidents above 125cc could be avoided due to ABS.

Two-wheeler rider behaviour during a pre-crash phase: Operating brakes on two-wheelers is complicated as compared to four-wheelers. Most motorcycles have separate controls for front and rear brakes. They are inherently less stable than four-wheelers and rely on rider skills to remain upright during extreme manoeuvres. In every fifth accident (17%) of the relevant cases in a study, the rider used only brakes. A majority (40%) of riders tried to avoid collision only by manoeuvring; 26% attempted both braking and steering; no reaction was observed in 8% of the cases who did not attempt any pre-crash manoeuvre. In two-wheeler ABS-relevant accidents, nearly half of all riders braked or braked-and-steered prior to crash; and 40% of all riders only steered prior to crash without braking. Thus, it is assumed that riders would benefit from ABS technology in these situations.

With two-wheeler ABS, wheel-lock is prevented even when the rider applies full braking power. Therefore, a fall-down or flip-over can be avoided; the two-wheeler as well as the rider can remain stable; vehicle speed is significantly reduced; and upright seating position of the rider can reduce severity. The benefit of two-wheeler ABS is estimated to be 33%; in other words, every third accident with casualties involving a two-wheeler on Indian highways (assuming 100% installation of two-channel ABS) could be avoided and further mitigation potential is seen in 16% cases where a reduction of collision speed has been calculated.

Our recommendations

As first protection, the use of a helmet should be encouraged in order to prevent fatal injuries. The observation of its use should be enforced. Then, besides infrastructure, education and enforcement, additional accident avoidance potential is given by vehicle safety systems. Customers should be informed and encouraged about the capabilities of safety systems such as the ABS technology. Even a low-cost solution such as a single channel ABS (front) is estimated to have high accident avoidance potential, thus it should be considered as standard for each two-wheeler.

Excerpts from a paper presented at SIAT 2015 by Thomas Lich (Robert Bosch GmbH), Girikumar Kumaresh (Robert Bosch Engineering & Business Solutions), and Joerg Moennich (Robert Bosch GmbH)

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