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The terms ‘self-driving cars’ and ‘driverless’ cars aren’t actually as interchangeable as people might think. The Society of Automotive Engineers (SAE) has ranked vehicle autonomy in 6 levels starting with no automation at 0 at which human drivers are in total control with no automation input, and full automation at 5 at which the vehicle is in total control with no human input. With an abundance of acronyms signifying various autonomous actions, drivers could be forgiven for wondering exactly where manufacturers have got to in terms of self-driving and autonomous vehicles.

  • Self-driving cars and driverless cars are not the same.
  • Vehicle autonomy can be ranked by 6 levels.
  • Drivers can understandably be confused by the differences.

SAE level 0 is a car that has no automation at all and is entirely within the manual control of the human driver.

SAE level 1 known as driver assistance means that a human driver can always take over, for example when using cruise control or lane assist, but some systems such as braking or steering can be automated.

SAE level 2 represents partial automation. At level 2, drivers are still required to take control, for example if there is an obstacle in the road, but otherwise the vehicle can control the majority of the actual driving with a combination of, say, adaptive cruise control and lane assist.

SAE level 3 is known as conditional automation. Although the human driver is available to take control, in most situations the vehicle can actually drive itself independently in particular conditions such as severe congestion or traffic jams.

SAE level 4 is called high automation. Human intervention will be necessary (indicated by the car) in very occasional circumstances but mainly the vehicle can drive itself. It’s at level 4 where the line between driverless and self-driving become less clear as a driverless taxi without pedals or wheel may be deemed level 4, yet some vehicles could still have the usual pedals and steering wheel.

SAE level 5 reaches full automation in all locations and all driving conditions without any human input whatsoever, but it is still a long way off as the predictability of the car’s driving environment can’t be guaranteed, for example, if a person decided to cross the road at a random point rather than a designated crossing.

Currently, only one manufacturer has received level 3 certification after meeting the international standard UN-R157, but these vehicles are not as yet available in every marketplace. However, there are ongoing pilot schemes for self-driving cars for taxis and buses in various locations worldwide.

In the UK, certain parts of self-driving tech – the use of traffic jam assist – has been legal since 2022 but there are no eligible cars as yet on the government’s designated list.

A cautious approach is understandably being taken to the development and roll out of self-driving cars, despite suggestions that 2025 is the year that they will be seen on the roads. Nevertheless, progress continues, and it’s been estimated that the developments made in advanced driver systems technology could ease the impact of accidents or lessen the number of collisions by up to a quarter.