Self-driving cars explained: how autonomous is my car?

‘Autonomous’ and ‘self-driving’ are words you’ll see a lot of when reading about cars at the moment, but what do they mean? We explain how the government categorises the different levels of car control

Words By Jimi Beckwith

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Autonomous driving

The government’s driverless car consultation aims to smooth the road to autonomous cars by fine-tuning the Highway Code, insurance laws and other legislation.

During the consultation, the government sorted the progress of autonomous - or driverless - cars into six levels, from zero to five. Using our explanation of the government’s categories, you can place your current car or choose your next car by identifying where it sits among the six levels of autonomy.

These six levels are:

Level 0

In level zero driving, the driver is completely in control of the car, in both speed and steering, with only warnings and alerts assisting the driver in extreme circumstances. Today, such cars are rare, and are almost invariably extreme, low-volume performance cars – the lack of driver assistance is said to create a 'purer' performance car.

Example: Noble M600 - no assistance systems fitted – the driver is in full control of the car at all times.

Level 1

Level one is the first of the ‘assisted driving’ levels, where the car can ‘support’ driving functions, meaning that the car has a small level of control in the journey.

Most modern cars can be considered to be of this level, as systems such as adaptive speed steering, speed limiters, traction control and ABS have the car controlling certain elements of travel in spite of the driver’s command. Very little control is given to the car, and the control that is given is often unnoticed.

Example: Skoda Fabia - traction control: when the car loses traction under acceleration, the car cuts the amount of power delivered to the wheels to stop them from spinning.

Level 2

The second level of ‘assisted driving’ as set out by the government ‘can control lateral or longitudinal movement’. Examples of this are adaptive cruise control, which changes the speed of the car based upon the speed of the car in front, or lane keep assist, which may adjust the steering if the car senses danger caused by drifting out of its lane accidentally.

At no point is the driver not paying attention to the road, nor are they taking their hands off the wheel. In the example of adaptive cruise control, the driver needs to keep the pedals covered in case of an emergency.

Example: Lexus NX 300h - adaptive cruise control: the car controls the speed at which it is travelling, but the driver controls everything else and must maintain focus on the road.

Level 3

Level three driving involves near-equal input from driver and car. An example of this type of car is a traffic jam assist system which will operate the accelerator, brakes and steering in slow-moving traffic.

Despite the car’s control in these situations, the driver must focus on the road and take control when necessary, making it a temporary ‘hands-off’ system but not an ‘eyes-off’ one.

Example: Seat Ateca - traffic jam assist, which can control all of the driving functions of the car, but you must keep your eyes on the road.

Level 4

The first of the ‘automated driving’ categories is also the first ‘eyes-off’ and ‘hands-off’ category. We’ve not yet seen a car on the market that fits category four, but with the government’s intention to make the UK a leader in autonomous car development, it shouldn’t be long.

The government describes this style of driving as “driver is only responsible and exercises control when the system is not in use”, while the car can be in charge of all driving functions, without the driver’s intervention, attention or input. The systems can be turned off when the driver chooses, and this is when normal driving resumes.

Example: none available yet, but the first self-driving cars should appear in around 2018

Level 5

Put simply, level five, the highest level of automated driving, is where the car can control its speed and direction fully, without any need for driver intervention. Although the government guide did not specify it, this type of autonomous driving would allow the car to drive on its own without an occupant; similar to the ‘summon’ feature on Tesla cars, which allows the driver to summon the car to them remotely. Level five vehicles are often referred to as ‘fully autonomous’.

Example: none available yet, but the first fully autonomous cars are expected to appear in around 2025

Self-driving car glossary

Autonomous Cars on the upper three levels are often described as ‘autonomous’, as the term can be applied to any car which can drive itself. This is why the word is interchangeable with the terms ‘driverless’, ‘self-driving’, ‘piloted driving’ and others.

Connected car Connected car technology is another widely used term in modern motoring and applies to technologies that allow cars to communicate with other cars and, when the technology becomes available, to a central information database. The communication will allow cars to update each other with changes in road terrain, safety hazards and other information that will allow them to become fully autonomous safely.

Eyes-off When a car can drive itself proficiently enough that the driver no longer needs to pay attention to the road, the term ‘eyes-off’ is used.

Hands-off When a car can take over functions of driving proficiently enough that the driver doesn’t have to have their hands on the wheel or their feet on the pedals, the term ‘hands-off’ is used.

Internet of Things The ‘Internet of Things’ is a term that applies to the use of the internet to connect more everyday objects – including cars, mobile phones and even household appliances – to the internet, allowing them to communicate with one another. In the context of cars, it will eventually allow the remote summoning of cars, as well as access to different functions of the car – such as the climate control and security features - from afar.

Semi-autonomous A car with autonomous systems such as lane keep assist, which are not active when the driver chooses them not to be, are widely regarded and often referred to as ‘semi-autonomous’.

Want to learn more about self-driving cars? Our full guide is right here

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