Safety-assist systems are helping to prevent crashes
A lot of physics are involved in a moving car. Weight, mass, speed, friction, energy and other techie stuff. Geometry is there as well with pitch, roll and yaw ... and you thought you'd never need maths again.
All those forces and actions are applied to just four smartphone-sized patches of rubber between you and the road. As the driver, you have the most control over just one of them with your right foot.
Too much speed, braking at the wrong time, tight turning angles, loss of friction because of slippery road conditions are just some aspects that can mean those small patches of rubber can't cope. That's when a good day can turn bad.
Then the engineers in the car-making factories invented anti-lock braking systems (ABS), which does exactly what its name suggests by preventing the wheels from locking when you brake - allowing you to steer the vehicle while safely bringing it to a stop.
Electronic brakeforce distribution (EBD) goes a little further than ABS with a collection of sensors that detect what impact all the various forces have on the car -- and then control the level of braking on each wheel independently.
Typically, the front end of a vehicle will carry the most weight so the EBD applies less pressure to the rear brakes, preventing them from locking and causing the car to skid.
EBD and ABS
Under heavy braking without ABS and EBD, typically the wheels will lock and the friction created between the road surface and the tyre will slow the car to a stop.
In a straight line on a dry, sealed road, this usually isn't a problem beyond needing a longer stopping distance and creating a flat spot on your tyre. Add in a bit of rain or a slippery surface, such as gravel, ice or snow, and the stopping distance has to increase.
By itself, ABS improves that situation significantly, preventing the wheels from locking and bringing the vehicle to a stop in a more controlled way.
When the wheels lock up on a corner, the angle that the front wheels are turned becomes irrelevant as the car's mass opts for a straight line which could mean crossing the white line into oncoming traffic, finding a ditch or meeting a tree.
Control of the car relies on its wheels continuing to turn. Under heavy braking, sensors monitor wheel speed and release pressure on individual wheels. Modern systems have individual brake lines to each wheel and can compensate for friction changes on different road surfaces. Less brake pressure is needed to lock a wheel on icy or gravel roads, compared to tar sealed surfaces.
EBD and ESC
EBD can also work with electronic stability control (ESC) to manipulate the speed of acceleration when cornering.
In most cases, taking a corner at speed will lead to understeering, when the nose doesn't swing around as much as you expect, or oversteering, when the car turns quicker than intended potentially forcing the back end to slide out.
To avoid this scenario, ESC employs something called a yaw rate sensor to detect the angle of the steering wheel and the direction that the vehicle is turning.
If the yaw sensor detects oversteer or understeer from different angles between the steering wheel and the tyres, ESC will activate one of the front or rear brakes to rotate the car back onto its intended course.
ABS braking helps prevent wheels from locking and EBD applies the appropriate brake force to allow ESC to work effectively and easily. Combined with consistent and safe driving, these safety-assist technologies are helping to prevent crashes.
Manufacturers continue to add to the suite of safety assist and crash prevention technology on board cars and, while this technology is reliable, it is only as good as the sensors that enable it to work. So, if you see a warning light illuminate on your dashboard, get it checked.