Both traditional car makers and leading tech companies are developing cutting edge technology for one of the most revolutionary markets of the next decade.

Billions of pounds have been invested in research and development. ABI Research has forecast that the year 2025 will see eight million autonomous or semi-autonomous vehicles.

SAE (Society of Automotive Engineers) levels rank the intelligence level and automation capabilities of vehicles from 0 to 5. From fully manual to fully autonomous capabilities, here is a guide to what each level means.

Level 0: Fully manual vehicle

The majority of vehicles on the road today are level 0, i.e. all aspects of driving are fully human and manually controlled.

Level 1: One single automated aspect

This is the lowest level of automation. A level 1 vehicle has a single aspect of automation that assists the driver with ADAS e.g. steering, speed or braking.

Level 2: Automated steering and acceleration

The vehicle is able to control both the steering and acceleration/ deceleration ADAS capabilities, although the driver remains in complete control of the vehicle at all times. Examples of level 2 include helping vehicles to stay in lanes and self-parking features.

Level 3: Environment detection

Able to detect the environment around them, level 3 vehicles contain the lowest tier system classified as an automated driving system. This more advanced technology allows level 3 vehicles to make informed decisions such as overtaking slower moving vehicles. However, unlike the higher rated autonomous vehicles, human override is required when the machine is unable to execute the task at hand or the system fails.

Level 4: No human interaction required

The key difference between level 3 and level 4 automation is that level 4 vehicles are able to intervene themselves if things go wrong. These cars can cope without any human intervention in the vast majority of situations.

Level 5: Human driving is completely eliminated

The top level of autonomy with an advanced environment detection system, this is where the car makers want to be – the future is driverless.