Brakes, Braking and Road Safety

Introduction to Brakes and Road Safety

The ability to brake safely is an important requirement for safe driving. Safe Braking is especially important for the most vulnerable road users such as pedestrians, cyclists and motorcyclists, as crash data shows these categories are all too often the victims of inattention by car, van, truck and bus drivers.
Vehicle manufacturers are continuously striving to develop better braking systems and technology such as Autonomous Emergency Braking (AEB) in an effort to increase safety and reduce accidents.
Safe braking however involves more than merely knowing how much pressure to apply to the brakes – safe braking also involves working out the relevant stopping distances etc.
In this section we will provide an overview of the importance of safe braking for road safety.

What is a Brake? 

The simplest definition would be that a brake is a mechanical device which inhibits motion. Almost all wheeled vehicles have a brake of some sort. Brakes may be broadly described as using friction, pumping, or electromagnetics.
When the brake pedal of a modern vehicle with hydraulic brakes is pushed, ultimately a piston pushes the brake pad against the brake disc which slows the wheel down. On the brake drum it is similar as the cylinder pushes the brake shoes against the drum which also slows the wheel down.
Brake pads are a part of the disc braking system, which is standard equipment for modern vehicles. In a disc braking system, a calliper is situated around the front wheels of your vehicle (most of a car’s stopping force comes from the front tires). The calliper is fitted with brake pads. When you press the brake pedal, the calliper squeezes the brake pads against the wheel and the resulting friction slows your vehicle to a stop.
It is also important that we are aware of 2 important modern brake systems and their impact on road safety.
  • ABS [Anti-lock braking system]is an automobile safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up (that is, ceasing rotation) and therefore avoiding skidding.
  • Autonomous Emergency Braking (AEB) is an autonomous road vehicle safety system which employs sensors to monitor the proximity of vehicles in front and detects situations where the relative speed and distance between the host and target vehicles suggest that a collision is imminent. In such a situation, emergency braking can be automatically applied to avoid the collision or at least to mitigate its effects.

What is the required Following and Stopping Distance?

Stopping distances refer to the distance that it takes for your vehicle to stop. Many vehicle crashes can be prevented if drivers allow themselves enough time and distance from the vehicle in front. This is referred to as a safe following distance.
Drivers are advised to drive at a speed that will allow them to stop safely within the distance available to them. The recommended stopping distance measured in time is at least two seconds. Safe driving involves keeping at least two seconds behind the vehicle in front, and is measured using a fixed point – when the vehicle in front passes a fixed point, it should be at least two seconds before you also pass the same point.
It is also important that the reaction time of the driver remains uninhibited and non-distracted as this could further extend the stopping distance.

Which Factors are affecting the Braking/Stopping distance? 

An effective braking system and driver ability behind the wheel are most important to ensure swift and safe braking. There are however also a few other factors to consider:
  • Tyres and braking: Tyres are one of the most important elements when stopping a vehicle quickly and efficiently. One of the factors used in calculating braking distance is traction coefficient. The higher the traction coefficient is, the shorter the braking distance will be. Braking distance can change greatly based on the type and condition of the vehicle’s tyres. Tyres with little or no tread will be more susceptible to skidding during heavy braking. When the tyres skid (a decrease of the traction coefficient), they lose traction and increase the braking distance. The tyre compound or makeup can also change braking distance. Some high performance tyres offer better adhesion under heavy braking and won’t break loose or skid as easily as harder tyres.
  • Braking and Suspension Systems: If any of these components aren’t up to specification or in poor condition, the vehicle’s braking distance can change. Worn brake drums, rotors, pads, shoes or leaky brake lines will have an adverse effect on braking. Since weight transfer has so much to do with braking, worn shock absorbers and springs will only add distance during braking. When these components are worn, the weight wants to move to the front of the vehicle when you hit the brakes hard. [See Shock Absorbers and Safe Driving]
  • Road conditions: The condition of the road and our ability to adapt to these conditions will affect braking distance. Dirt and gravel roads don’t offer good traction and increase braking distance. Freshly paved asphalt offers the best adhesion.
  • Weather Conditions: We always need to consider the weather conditions and how this impacts on the road surface and the vehicle. Wet roads increase braking distance. Snowy and icy roads decrease traction even more.
  • Driver ability: Driver experience and knowing your vehicle are important for safe and fast braking. Drivers can only benefit from additional driver training and advanced driving courses to enhance their driving skills.
  • The Braking system: Whether or not the vehicle is equipped with an anti-lock braking system (ABS) must also be taken into consideration in calculating stopping distances.

Formula to calculate Braking Distance

How do we calculate Braking distance? This distance refers to the distance a vehicle will travel from the point where its brakes are fully applied to when it comes to a complete stop. It is affected by the following:
  • original speed of the vehicle
  • the type of brake system in use
  • the reaction time of the driver/rider and
  • the coefficient of friction between its tires and the road surface.
The theoretical braking distance can be found by determining the work required to dissipate the vehicle’s kinetic energy.
The kinetic energy E is given by the formula:
E = (1/2)mv2,
where m is the vehicle’s mass and v is its speed.
The work W done by braking is given by:
W = μmgd,
where μ is the coefficient of friction between the road surface and the tires, g is the gravity of Earth, and d is the distance travelled.
The braking distance (which is commonly measured as the skid length) given an initial driving speed v is then found by putting W = E, from which it follows that
d = v2/(2μg).
The maximum speed given an available braking distance d is given by:
v = √(2μgd).
Note that these theoretical formulas do not take account of the driver’s reaction time (an example is the two-second rule).
[Info from Wikipedia]

Also view:

Advice and Tips on Braking Safely

We would like to share advice and suggestions with drivers on how to brake safely:
  • ‘Normal’ Braking: Under normal circumstances (on a dry and relatively clear road), you should be able to brake early and apply gentle pressure to the brakes. As you feel the vehicle begin to stop, apply a little more pressure, but ease off as you come to a full stop so that you do not stop too abruptly.
  • Emergency Braking: If an unexpected situation arises that requires you to stop, you should brake straight away, but try to avoid braking too sharply, as this can cause your wheels to lock up and your vehicle to skid. With ABS, depress the pedal all the way down. Without ABS, brake moderately hard (70%) while taking off a bit of steering. It’s always better to brake too much rather than too little. In a real emergency, it’s best to simply stamp on the brake pedal and let the car stop.
  • Braking in Bad Weather: If the road is wet or icy, you will usually need to alter your braking technique. This is particularly the case in icy conditions. It is extremely easy to lose control when taking a bend. The safest way to negotiate it is to brake gently on the straight leading up to a bend, so that you are travelling slowly when you reach the bend. Avoid braking sharply as this can lead to a skid. If you are worried about the grip (or lack of it) on the road, you can test it by braking gently to gauge the effectiveness. Do not leave it until just before a bend to test the brakes, as you will not have enough time to dry them out before you need to break.
  • Braking after driving through water: If you have to drive through a considerable amount of water, your brakes can lose their effectiveness for a while afterwards. Test the brakes by braking gently to see if they work properly, but make sure that you do this only when it is safe to do so. If you find that they do not work as effectively as normal, apply light pressure to the brakes while you are driving at a fairly slow pace, as this will dry them out.
  • Braking and Turning /Changing Direction: Avoid braking and turning at the same time where possible. Turning while on the brakes can cause the vehicle to not turn as well or not slow down as much.
  • Brake-Turning: Turning the wheel into the corner while still lightly on the brakes. This causes the car to lean forward, pressing the front tires to the ground, giving them more grip for steering. This is a basic technique, and no corner should be made without it.
  • Trail Braking: This is a method of feathering the brakes while turning into the corner and it will provide the best and safest control over the vehicle as it is leaning on the front tyres, allowing for more traction to those tyres.
Drivers are advised in an emergency to focus on where you want to go, and not on what you want to avoid. It’s very difficult to steer away from something that you’re looking at directly, and many people have a tendency to focus on what they are worried about colliding with. Instead, concentrate on where you want the car to go (to the side of the object) and pay attention to how the car responds.

Inspecting the Brakes

We are all aware of how important it is to brake safely – yet we often fail to pay enough attention to the condition of our brakes! This is an important part of effective vehicle maintenance.
If you do not feel comfortable with your own mechanical skills, it may be best to have a professional to check your brakes and to install new parts. Working on your own brakes is not the time to test your mechanical abilities. If your brakes are installed incorrectly or worn and the condition thereof not assessed correctly they may fail and cause a severe accident.
Brakes are pretty much the most important safety device on your car. Inspecting your brakes at least twice a year for wear and damage can protect you and your passengers while saving you money by catching any damage before it becomes too costly.
You are often able to inspect the brakes without even removing the wheel. If your car has alloy wheels with spaces in the middle, you can get a proper assessment done by just peeping through the hole! Whether you can peep through your wheel or you have to take the wheel off, be sure you have a clear view of the brake pads and the big shiny disc.
You may start by inspecting the disc first. It should be shiny from the inside to the outer edge, and fairly uniform. Do not be too concerned if you can see slight lines in it as this is normal wear. However, if there are any rough spots or pronounced grooves in the disc, you should replace your brake discs. Brake discs should always be replaced in pairs so that your car’s driveability and safety are not compromised.
Now take a look at the Brake pads. You’ll have to peek up to see them, but if you follow the surface of the disc to the top, you’ll see the outside pad touching the disc. Brake pads must be replaced when the thickness of the friction material is at 2mm thick, or when uneven wear is evident on the brake pads.
Finally, take a look at your brake lines. Rubber coated lines should be soft and supple, not cracked and rigid. If you see cracks in flexible brake lines they will need to be replaced. Also be sure to inspect the hard, metal lines.

Brake Pads and Safe Braking

The brake pad is one of the most important components in your braking system; it is the part directly responsible for stopping your car. However, brake pads are not built to last – As you use your brakes in everyday driving, they will slowly wear down, and, eventually, need to replace the brake pads. Therefore, it’s important to understand how brake pads work and when to replace them.
Brake pads are soft (from an industrial standpoint), so that they don’t erode the wheel while they are in use. Instead, the friction wears away at the brake pad, which is an easily replaceable part. Over time, the brake pads erode away with use and must be periodically replaced. There are a number of variables that affect how often you need to replace your brake pads, but they basically boil down to the model of car you drive, your driving behaviour and how often/hard you apply your brakes. Generally, brake pads may need to be replaced every 30,000 kilometres. Best advice is to have them checked regularly.

How do I know the brake pads need to be replaced?

Mechanics will easily assess when the right time would be to replace the brake pads – but there are some other warning signs for the driver as well. A sure alert that you need new brake pads on older vehicles is squealing.
Brake pads on older vehicles actually have a sort of built-in alarm system to alert you when they need to be replaced. There is a little bit of metal that pokes out of the brake pad. When the pad is worn down enough, this metal comes into contact with your wheel every time the brakes are applied. This creates a squealing or screeching sound every time you apply the brakes.
Take warning though: waiting until you can hear your brakes screeching to replace your brake pads is not the best idea. The bit of metal is not exposed to the wheel until there is very little brake pad left. Once you can hear screeching, it generally means that your brake pads have only three or four weeks left before they are completely worn away.  Without the brake pad, you’ll be stopping your car with metal-on-metal friction, which can warp your wheel, damage your brake system, and cause an expensive repair.
Modern cars today come with an electronic sensor on the brake pad. When your brakes have worn down, you will see a warning light on your dashboard. When this dashboard light is illuminated, or when you start hearing a squeak upon brake application, it is time for you to have your brake pads replaced.
[There is much more to a braking system than merely the brake pads. See below as well the guides to changing brake discs, brake drums, brake shoes and brake pads.]

Conclusion

Never overlook the importance of safe braking. We need to focus both on driver and vehicle fitness. If we are not caring for the vehicle components required for safe braking we are not only causing damage to the brake as a whole, but we are taking a big safety risk.
Be sure to use a great deal of care when replacing your brake parts. It is recommended that you have your brakes checked each time your vehicle’s oil is changed – about every 10,000 kilometres. This quick inspection, paired with proper maintenance of your brake pads, will prevent problems down the road, ensuring the safety of you and your family.
This article was taken from: https://www.arrivealive.co.za/brakesbraking-and-road-safety
Run-Flat tyre technology

Introduction / Description / History of Run Flat Tyres

During the past few decades the motoring manufacturers have made significant design contributions to the safety of all road users. Apart from seat belts, ABS and airbags, car manufacturers have also developed active driving assistance systems, such as traction control and computer-controlled stability programmes. More recently there has been a focus on tyre pressure monitoring systems (TPMS) and the development of tyres with run flat capability.

A run flat tyre is a pneumatic vehicle tyre that is designed to resist the effects of deflation when punctured, avoiding hazardous tyre changes and allowing the driver to continue the journey at a reduced speed. Run flat tyres have been described as the “first important revolution in tyre design since the invention of the pneumatic tyre.”

The speed and distance to be travelled to safety will depend on factors such as the amount of people in the car, whether the boot is fully loaded etc. It is best to follow the guidance provided by the tyre or vehicle manufacturer, but a rough guide would be the following:

  • With low loads, one or two persons without luggage:
    – Approximately 240 kilometres at a maximum speed of 80 km/h
  • With moderate loads, two persons with full luggage or four persons without luggage:
    – Approximately 145 kilometres at a maximum speed of 80 km/h
  • With a full load, while towing a trailer or four persons or more with full luggage:
    – Approximately 48 kilometres at a maximum speed of 80 km/h

Run flat tyres were first patented in 1892, re-developed in 1978 and offered as an option in the 1990s mainly for two-seat sports cars with little room for spare tyres and jacks. These tyres have since become popular with manufacturers of high-end luxury cars, because of their safety and convenience, costing double the price of sports tyres.

Run Flat Tyre Technology and Road Safety

 

How does Run-Flat Technology work?

It is important to consider how a tyre loses air pressure and how the run flat tyre manages to ensure safety and continuous driving.  A tyre loses air either through penetration or a cut to the tread or sidewall area, usually causing loss of control of the vehicle or forcing the driver to stop and change the tyre.

Run flat tyres work like conventional tyres. They still contain air; to reduce the load that the run-flat system has to bear, to spread the weight of the vehicle evenly on the road surface, and to maximise the contact patch between the car and the road. Once run flat tyres detect the first signs of deflation (usually caused by punctures), it automatically applies a number of counter-effects to ensure safety and continuous driving.

A run flat tyre offers a very high standard of driving comfort; the driver will barely notice any loss of pressure in the tyre. For this reason these tyres are used on vehicles equipped with a tyre pressure monitoring system, which will display the drop in tyre pressure on the dashboard instrument panel.

There are many different types of run flat tyres from a variety of tyre manufacturers. We can however identify 3 basic technologies:

– Self-supporting

The tyre is built with stiffer side-walls (sometimes 50% thicker) that can bear the weight of the vehicle even when the pressure within the tyre is greatly reduced. The side-walls are typically constructed of layers of rubber and a heat-resistant cord that prevent the side-walls from folding or creasing. The bead around the edge of the tyre is also specialized to grip the wheel rim such as to avoid becoming detached from the rim. The tyre’s side walls are usually made of an extra layer supported by a heat-resistant cord to keep the tyre in the original position even under the weight or road bumps.

– Self-sealing

These tyres contain an extra lining within the tyre that self-seals in the event of a small hole due to a nail or screw. In this way, the loss of air is prevented from the outset so that that the tyre is either permanently self-repairing or at least loses air very slowly. This type is usually less efficient as it still allows the air to get out of the tyre – until the seal comes into effect. Additionally, it could fail to stop the deflation completely, but still it could allow the driver to reach the first service centre.

– Auxiliary-supported

In this system, there is an additional support ring attached to the wheel that can support the weight of the vehicle in the event of a loss of pressure. While these systems generally offer better ride quality because their sidewall’s stiffness can be equivalent to a standard tyre, the requirement to have both special wheels and special tyres increases cost and limit these systems from widespread use.

 

Run Flat Tyre Technology and Road Safety

 

Benefits of Run Flat Tyres

Run flat tyre technology has been developed as a solution to overcome the danger of a tyre deflating while you’re driving or changing a tyre next to the road. Run flat tyre technology does away with concerns about flat tyres and the added dangers of fast moving traffic, poor visibility, bad weather or criminal activity on the roads. The run flat tyre enables safe driving from the point when a puncture occurs until the driver can drive the vehicle to a safe location.

The benefits of run flat tyres could be summarized as follows:

  • Safety and reduced risk of accident – blowouts and tyre deflation can be serious driving risks for drivers.
  • Safer handling – the run flat tyre protects the car and maintains handling on the road.
  • Reduced danger and stress in the event of a flat tyre.
  • Safety from criminal element on the roads – no need to stop in areas of risk/dangerous crime areas.
  • Increased customer safety for night driving or women driving alone.
  • Convenience – it is not necessary to stop immediately to change a tyre and the journey can be continued.
  • Insurance benefit – using run flat tyres can decrease insurance premiums, as insurance companies want to provide an incentive for customers to increase safety.
  • Increased luggage space – the absence of the spare tyre means more luggage space so the driver could use the additional room for other purposes.
  • Increased space could contribute to improved integration of alternative power in future generations of automobiles.
  • The absence of a spare wheel contributes to lower vehicle weight which will in turn reduce fuel consumption, reduce harmful exhaust emissions, improve performance, handling and braking characteristics.
  • Tyre pressure monitoring devices warn the driver of a tyre pressure loss.

 

Run Flat Tyre Technology and Road Safety

Warnings and Negatives of Run Flat Tyres

We have detailed the many benefits of run flat tyres, but this raises the question – why do we not find many more vehicles with run flat tyres. Why do we only find a small percentage of vehicles with these tyres?

We also need to provide some insight and share the criticism raised about run flat tyres. The critics who see these tyres as a waste of time and money warn that:

  • The cost is an important aspect of a run flat tyre. Run flat tyres can be substantially more expensive than conventional tyres, and there is some dispute about the tread wear over the life of the tyres.
  • Installing such a tyre is obviously more expensive than fitting the car with regular ones, thus raising the overall price of the car – manufacturers argue however that the various safety advantages of run flat tyres is more than enough reason to counter this argument.
  • Run flat tyres require the presence of tyre pressure monitoring sensors. The system is there to inform the driver of a tyre that is losing pressure.
  • These sensors can either be a “Valve and Sensor Unit” or a Sensor strapped to the inside of the rim and can be rather expensive if not standard equipment on your vehicle.
  • Repairing/replacing a run flat tyre that got damaged after using it is considered too costly in many cases.
  • Some run flat tyres have a 20 % higher rolling resistance, in part due to their added structural material and mass; this can worsen a vehicle’s fuel efficiency.
  • A heavier tyre could translate into reduced engine performance, increased fuel consumption – or lower fuel efficiency – and, in some cases, reduced braking performance. The latter is obviously the most important, but thanks to some new developments in the run flat technology, this appears to be getting solved.
  • The overall weight increase of the tyres may be slightly offset in a vehicle by the elimination of a spare tyre and tyre jack, although the fact that the run flats are “unsprung” weight makes this an uneven trade.
  • The excess tyre weight is around the perimeter of the tyre, which increases inertia/momentum of tyre rotation, slowing acceleration and increasing stopping distances.
  • These tyres may be stiffer, making for a stiffer ride which can be an issue for some drivers.
  • Many cars designed for use with run flat tyres lack an area for a spare tyre, which means that if a driver opts to switch to conventional tyres, there might be no room for a backup in the event of a flat tyre.
  • Once the run flat tyre comes into effect, the driver will have to reduce speed and drive carefully – some critics say that for some drivers, especially those with less experience, driving with a run flat tyre could cause mental or emotional stress which could threaten the safety of other road users…[This would however be only a short drive!]
  • A shortage of both replacement tyres and trained repair facilities is a further criticism. [In the US a few tyre manufacturers have been named in lawsuits citing various forms of product misrepresentation.]

Many of these concerns are being addressed by vehicle and tyre manufacturers. It is however important that the road user and vehicle owner are alerted to these points of criticism. This will allow the vehicle owner to raise any points of concern with the vehicle dealer and gain much needed peace of mind!

 

Advice for the Driver with Run Flat Tyres

Whether you are the vehicle owner or the driver of a vehicle with run flat tyres, it would be worthwhile to consider a few safety aspects before going on the road.

  • When properly used, run flat tyres meet the highest standards in terms of safety and handling characteristics.
  • It is best to always check with the guidance provided by your vehicle manufacturer/tyre supplier on how to use these tyres.
  • Before you start your journey make sure whether you have run flat tyres or conventional tyres – confirm that it is a run flat tyre by checking the sidewall for the mark of identification.
  • Run flat tyres should only be fitted on vehicles equipped with a tyre pressure monitoring system and preferably where the tyre was fitted as original equipment by the vehicle manufacturer.
  • Vehicle manufacturers recommend the fitment of approved wheel and tyre combinations, as non-approved wheels or tyres may make contact with the vehicle body due to impermissible tolerances, even though they are the same size.
  • It is not recommended changing the fitted run flat tyres to conventional tyres, because of constructional difference it may influence handling and performance.
  • In the case of an emergency it is possible to fit a standard tyre to the car – if the vehicle has a spare tyre.  This can only be a temporary solution for a limited time. The standard tyre must also comply with recommended speed and load recommendation from the vehicle manufacturer.
  • Vehicles fitted with run flat tyres in most cases do not have a spare tyre. If you wish to change to conventional tyres, it is recommended that you consult with your local vehicle dealer to obtain written confirmation. The Dealer must also include which tread pattern and sizes to fit if a conventional tyre is allowed.
  • Run flat tyres can be repaired as with other tyres. If the hole is in the belt or crown area, a mushroom plug repair can be done for temporary emergency measures, but the tyre should be replaced at the earliest possible convenience.
  • Repairs cannot be carried out in the shoulder or sidewall areas like with conventional tyres.
  • Manufacturers however recommend run flat tyres are replaced and not repaired, as it is difficult to know exactly what damage has been caused to the tyre once deflated.
  • Special care is needed when mounting or de-mounting a tyre to a rim where a pressure sensor is used – rather use professionals to change these tyres.

 

Conclusion

Safe tyres are very important safety components on each and every vehicle. Not only are they important for steering and proper vehicle control, but also for speedy and effective response in the event of emergency and accident avoidance. On South African roads we have the added danger of both questionable road conditions off the main roads – and criminals preying on drivers and passengers in distress. If it is possible to avoid stopping next to the road to change tyres – this could only benefit the safety of drivers and passengers.

We can expect that run flat tyres will increase in popularity and be an important addition to many of the newer vehicles on our roads!

Also view:

Run Flat Tyre Technology and Road Safety

This article is taken from: https://www.arrivealive.co.za/run-flat-tyre-technology-and-road-safety

Open chat
Scan the code
Hello 😊 How can we assist you today?