E.g. if the car is moving at 20 mph the thinking distance will be 20 ft and if the speed of the car is doubled to 40 mph the thinking distance will become 40 ft, thinking distance is directly proportional to the speed of the car.
Overall breaking distance can be affected by a number of variables. There are three components to overall stopping distance these are: Mental processing time, Movement time and response time.
Mental Processing Time:
This is the time it takes for the driver to detect something. For example it is the time required to detect that a pedestrian is walking across the road directly ahead and to decide to apply the brakes.
Movement Time:
Once a response is selected the driver must perform the required muscle movement, for example the time it takes to lift the foot off the accelerator pedal and press the brake pedal. Movement times can be effected in many ways, the more complex the movement the longer it will take to complete while practise lowers movement times.
Response Time:
Mechanical devices take time to actuate, even after the driver has acted. For example the driver stepping on the brake pedal does not stop the car immediately. Instead the stopping is a function of physical forces, gravity and friction.
Thinking distance is affected by many factors:
The thinking distance is affected by the speed of travel because the faster the vehicle is travelling the longer it would take for the driver to think. For example if a car is travelling at 20 mph it will take 20 ft thinking distance and if the car is travelling at 30 mph the thinking distance will be 30 ft, the speed of travel does affect the thinking distance.
Thinking distance is also affected by the effects of drugs and stimulants because when you are under the influence of drugs your reaction time will be slower which will dramatically increase the thinking distance, it will take more time for the driver to react and put the foot on the pedal, this will also affect the overall stopping distance. Stimulants make the driver more alert and more awake so when the driver has taken stimulants and energy drinks their thinking distance will decrease meaning quicker reactions and a lower overall stopping distance.
Alcohol also affects the thinking distance because when the driver is under the influence of alcohol and is driving it will take longer for them to respond to something even if they are under the legal speed limit, it will make the driver brake later than normal which could mean braking to late and their thinking distance is also going to increase.
Thinking distance is also affected by the age and health of the driver. The age of the driver effects the thinking distance because if the driver is over 70 years old it would take them longer to react than someone aged between 30 to 40 years because as a person gets older their health starts to deteriorate and start to become slower than they used to be, this will increase the thinking distance because if it takes longer to process the information it will increase the reaction time whereas if someone is aged 16 to 19 years their reaction time may also be slower because they may be inexperienced, people aged between 30 to 50 years will probably have better thinking distances because they wont be too old and have slower reaction times and they wont be too inexperienced. Although the driver is old this may be compensated because as the driver gets older they tend to decrease speed which they drive at.
Illnesses can affect safe driving, there are various illnesses that can be dangerous for drivers these include the following:
- Blackouts
- Vision Problems
- Epilepsy
- Heart disease
- Sleep Disorders
- Diabetes
- Psychiatric Disorders
- Age-related decline
This usually won’t mean they cannot drive at all, but they may need to see their doctor more often and they may possibly need to restrict driving.
Health also affects thinking distances because if the driver has a mental problem they will take a lot longer to react than an ordinary person, or if the driver has other health issues such as arthritis, that person will have slower reaction times.
Distractions such as mobile phones, in car navigation systems, adjusting the stereo and large roadside billboards increase thinking distances because while the driver is driving they will need to pay full attention to drive and safely control the vehicle and respond to any activity on the road or nearby. Distractions cause the driver to do the following, take their eyes off the road, take their mind off the road and take their hands off the steering wheel. When driving you may be distracted by more than just one distraction e.g. if you want to put the volume higher on the stereo you take your hand of the steering wheel to turn the button and you take your eyes off the road to look at what button you want to press. This will make the thinking distance of the driver increase massively which will make accidents occur more easily as they are not concentrating.
Using a mobile phone is a distraction from driving safely; it divides a driver’s mental attention away from the road meaning that drivers may miss road signs, warnings and hazards. Using a mobile phone increases the time it takes the driver to react.
Tiredness makes the human body do things slower than usual, such as thinking; this will make the brain work slower as the body will be trying to rest. Tiredness causes thinking distances to increase as the mind would be slower and the reaction time would also be slower, so it will increase the thinking distance a lot.
The braking distance is the distance the vehicle travels between when the driver applies the brakes and when the vehicle comes to a stand still and stops moving completely. Braking distances are not directly proportional to speed unlike thinking distances which are directly proportional to speed. The braking distance increases massively as the as the speed of the vehicle increases. For example if the vehicle is travelling at 30 mph the braking distance is 45 ft and when the speed of the moving vehicle is 40 mph the braking distance is 80 ft, when compared to 125 ft the vehicle is travelling at a speed of 50 mph. The rate of change is increasing as the speed is increasing for example when the car is travelling at 30 mph and 40 mph the increase in braking distance is 35 ft whereas the difference when the car is travelling at 40 mph and 50 mph the increase is 45 ft. The increase in braking distance is by 10 ft when the speed increases by 10 mph, this is shown when the car is travelling at 60 mph the braking distance is 180 ft, the increase in braking distance has increased by 10 ft from 45 ft to 55 ft. this shows that the data does not have a consistent rate of change and is not directly proportional to speed. It doesn’t matter how alert the driver may be it mainly depends on the brakes because that is what brings the vehicle to a stand still. As the speed of the travelling car increases the braking distance also increases but not at a constant rate.
The braking distance is affected by many things, these are: Speed of travel, Conditions of tyres, Condition of brakes, Road conditions, Mass of the vehicle and Aerodynamics.
The braking distance is affected by speed of travel because as speed increases braking distance also increases. When a car is travelling at a high speed the driver will have less time to identify hazards and react to what is happening around them, this is because when the vehicle is travelling at higher speeds objects around the road come and go faster so the driver has less time to react to the object or person. It takes vehicles further to stop when travelling at high speeds and if there is a crash injuries will be more severe.
The braking distance is affected by the speed the vehicle is travelling at. The faster you are travelling the further the car will go in that same time. A driver travelling at higher speeds will have covered more ground in between spotting a hazard and reacting to it. Also the slope of the road and the amount of friction between the road and tyres affects the braking distance.
Higher speed will cause both the thinking and braking distances to increase. The thinking distance can increase massively at higher speeds.
The condition of the tyres on the vehicle will be a massive factor of the braking distance. This is because when the tyres are brand new they have better grip to the road whereas if the tyres are used and are worn out. After the tyres have been used for a long time the grip deteriorates. The better the grip on the tyre the smaller the braking distance will be. The less grip a tyre has the longer the braking distance will be. The tyres tread must be above a certain size to be safe and legal on the road. The deeper the thread the more grip it has on the road and will result in shorter braking distances.
The condition of the brakes that are equipped to the vehicle will affect the braking distance because if the brakes are worn out it takes longer to stop, whereas if they are brand new and made by the use of modern technology that has evolved to become better and more effective at braking the braking distance will be much smaller. This is because when the brakes are brand new they have more grip to the tyre than old worn out brakes.
Road conditions can affect the braking distance a lot because when it rains or snows the road becomes slippery which makes the car skid and will make the vehicle take a longer distance to come to a stand still. When the roads are wet, the friction between the car’s tyres and the surface of the road is reduced. This can increase stopping distances and will do so dramatically if the weather conditions are bad and the depth of the vehicles tyres is shallow.
Car accidents are happening everyday at an increasing rate therefore braking distance is a vital part of scientific research. This is because modern cars are becoming faster and there are too many vehicles on roads. As velocity decreases so does the distance it takes to stop the vehicle. Gravel, grit and oil spills on the road disrupt the braking distance.
The weight of the car is a large factor for the amount of distance covered until the vehicle comes to a stand still. The heavier the car the longer it will take to stop, but this is not always the case as many cars are fitted with the high tech equipment which helps the car stop quicker even though it is big and heavy. The heavier the car the harder to make it stop, when the car is heavier it has more momentum which keeps the car moving even though your foot is of the accelerator.
Aerodynamic cars travel through air faster because air goes around the car instead of colliding on the front of it. This is because they are a streamlined shape and can travel through the air and have less air resistance acting against them. The less aerodynamic the car the better it will be at slowing down because air resistance will be helping the car to slow down, but the down side is that more fuel will need to be used which is bad for the environment, it will use more fuel because the engine will have to work harder as there will be air resistance acting against the car. Sports cars are very aerodynamic so they can travel at high speeds and reduce the air resistance working against the car. This is why they have very powerful brakes because they need something equally as powerful to stop the car. This is why so many sports cars are fitted with flaps that pop up when the driver presses the brakes, the flaps are there to create air resistance to help the car slow down. The more dynamic the car the longer it is to stop.
When an object is moving it has more than just velocity, it also has lots of energy. The term momentum is used to fully explain the vehicles motion. The momentum of an object depends on its velocity and mass. Objects that have a larger mass and higher velocity will have more momentum. Small objects can have a large momentum but they must be travelling very fast. For example a mouse and a cat are travelling at the same speed the one with the larger mass has the greater momentum.
The momentum of an object is measured in kilogram meters per second (kg m/s). To calculate the momentum of an object the following formulae is used:
Momentum = Mass x Velocity
= 20 kg x 20 m/s
= 400 kg m/s
In order to stop an object you will need to remove its momentum. To calculate the force needed to stop it in a collision you can work out its momentum. Sometimes this force can be too large and will almost definitely damage the thing you are trying to stop. You can decrease the damage that will occur by trying to slow something down by applying a lower force for a longer period of time. This is used in a cars safety design; they make the car with a design that can take the force for longer so less damage occurs in a collision. This is called the crumple zone. By doing this it reduces the impact on the car and also reduces the impact on the car it crashes into. Many lives are saved by this safety feature.
Stopping distances depend on many factors, such as speed, thinking distance and braking distance. This is shown on the table which is on the Highway Code. This table shows the approximate stopping distances. The figures and data given are only on typical and average cars but in reality the stopping distances are affected by the different speeds and circumstances which give a different outcome. The thinking distances will depend on the person, their age and if they are under any drugs or alcohol. The stopping distances will be different for everyone; the factors that affect the overall stopping distance are the age of the person, young or old, careless or under the influence of alcohol or drugs and if they have any health problems.
The braking distance will also be affected and will depend on the following:
- The condition of the brakes
- How good the brakes are
- How well the tyres grip onto the road, this can depend on the weather
- The road surface
- The condition of the car
- The weight of the car and its contents
The distances given in the Highway Code may be wrong because they are only averages, what if someone’s car is old or the distances may be better than the ones displayed because the car may be very modern and brand new. One of the factors that affect stopping distances are road conditions which most likely depend on the time of year and weather or if the road has not been newly laid for a long period of time. The condition of the brakes on the vehicle are also a major factor for braking distances, because if the brakes are old and worn out they will not perform as good as the brakes on a brand new car. Brand new brakes will perform better than old ones because as technology has developed there are modern materials and equipment for these brakes to be made for top quality and high standard braking.
The braking distance also depends on the road surface and what condition the surface is in, the weight of the car and its contents also determine the braking distances. One of the main factors that determine the braking distances is the vehicles braking capacity. This depends on many things, for example:
- Tyre pressure
- Tread and Grip
- The vehicles suspension
- Weight of the vehicle
- Road surface
- Brakes
There is some logic to the idea that top-down policies like speed limits, fines and road signs can only go so far in improving safety on the UK’s roads. What is really needed to tackle the root of the problem is a change in driving culture, in which drivers are more aware of their responsibilities behind the wheel. That can only be done through education perhaps as part of the driving test, or even by talking to people who are going to become drivers in schools. This improvement is due to a number of factors, including seat belts, improved car design, the breathalyser and traffic-calming measures.
Speed limits in many towns and cities should be reduced to 20 mph, say the governments road safety advisors. Their report claims a default speed of 20 mph in built up areas will help halve the number of deaths on Britain’s roads within the next few years. The study also called for greater enforcement of 20 mph zones through a new generation of speed cameras. The devices measure a driver’s speed over a certain distance and should be a priority for the Home Office. The camera’s are undergoing trials and still awaiting government approval for use in 20 mph zones.
Lowering the speed limit in towns from 30 mph to 20 mph will lower the number of deaths on Britain’s roads by 40%. The chances of a pedestrian being seriously injured or killed if struck by a car is 45% if the car is travelling at 30 mph whereas if the car is travelling at 20 mph the chance is only 5%. This will reduce so many deaths that happen in town at slow speeds.
The benefits of lowering the speed limit from 30 mph to 20 mph are: It will lower the number of accidents and deaths because at lower speeds cars can stop quickly and pedestrians will be easier to spot. At lower speeds crashes are far less likely to be fatal. At 20 mph only 10% of crashes are fatal compared to 50% at 30 mph. 20 mph zones have reduced collisions of all severities by 60%, those involving child deaths and serious injuries by 70%. This is proven as 20 mph zones in London have reduced all casualties by 42 %, deaths and serious injuries by 53%.
In hulls 20 mph zones serious and fatal casualties have fallen by 90 %. Lower traffic speeds will encourage people to cycle and walk, it also makes manoeuvres easier. Manoeuvres can be difficult to perform as there is high speed traffic on either side of you. The first is road safety. Hull city council has reduced overall injuries by 60% in its 20 mph zones. Child pedestrian injuries have been reduced by 75%. That’s a massive saving of human health and happiness. If speed is reduced it will become much easier. It will save the NHS a lot of money. Road accidents cost the NHS £470 million and the UK economy £18 million every year.
In short, making 20 mph the default speed limit on community streets would rapidly pay for itself through the money saved on health care and emergency services. 20 mph is the speed at which drivers can have eye contact with other users of the street. It is the speed at which pedestrians feel more confident about crossing the road, children play outside their homes and it is quiet enough to hold a conversation.
That might be a popular slogan for the pro-driving lobby, nut its difficult to argue with the statistics involved in the results of speed reduction. A comprehensive study into the effects a speed limit to 20 mph found that accidents of all types fell by 60%, with accidents involving children down by two thirds.
And the supporters of a wider use of a 20 mph limit also have some science on their side. A driver travelling at 20 mph is able to come to a sudden stop in almost half the time of someone driving at 30 mph. The total stopping distance for a 20 mph driver is 12 meters, compared with 23 meters at 20 mph.
The commission for Integrated Transport also found that area wide 20 mph limits are the one critical success factor underpinning best practise in promoting walking, cycling and public transport as alternatives to the private car.
Growing car use is one of the biggest reasons for climate change, not to mention deaths and injuries, obesity, decline in community life and one or two other problems of modern living. A 20 mph speed limit on most streets in built up areas is one thing that would do most to encourage people to walk and cycle – and leave the car at home.
Research has shown that areas with a 20 mph limit have a reduced rate of accidents involving children fall by two thirds in areas with the reduced speed limit.
The reduction in the speed limit is the answer to making urban roads safer. Simple physics shows that drivers can react and stop much faster when driving at 20 mph.
However the downsides are, all you achieve by making people drive down the road looking at their speedometer is 10 times as many deaths and that’s before you cause more accidents because people aren’t looking where they’re going.
The cost of deaths and injuries is massive. A review of 20 mph zones in London boroughs found that 20 mph would be suitable for implementation over the majority of the boroughs road network and if installed would have the potential to make large casualty savings. For example if 60% of the borough road network were treated and the results of this study was replicated, the killed and seriously injured number for the treated network could be expected to fall from 2,410 to around 1,040, This would equate to an annual saving of around £248 million. An additional reduction in the slight casualties may deliver savings of around £65 million. The cost of installing 20 mph on 60% or around 8000 km of borough road network has been roughly estimated at £230 million.
Opponents of tighter speed limits say that the measures can be counterproductive, forcing drivers to spend more time concentrating on surrounding the horizon for speed cameras and keeping an eye on their speedometers, rather than concentrating on the road in front of them.
A further danger of applying such strict limits in residential areas is that British drivers simply may not accept them or take them seriously, which could damage the credibility of speed limits more generally.
I t is just another way for the government and local authorities to collect fines from motorists.
By introducing unrealistic speed limits, drivers may be less inclines to obey limits as a whole.
A change in culture is needed to stop UK drivers from speeding. Simply lowering the limit will not tackle the problem, because many drivers love driving fast as they find it fun, there will need to be change in society about over speeding.
I think that the government should lower the speed limit because it will dramatically lower the amount of deaths and people who are seriously injured and it will also reduce congestion. There are more benefits of reducing the speed limit in towns than disadvantages and downsides so it easily out ways all the downsides of reducing the speed limit in a residential areas. By reducing the speed limit it will be saving many lives and will make the road a safer environment. They should reduce the speed limit as it will save the NHS a lot of money in the long run.