The boss of Toyota’s Research Institute believes the classification system for autonomous driving levels is causing confusion over the progress being made in the development of self-driving vehicle systems.

The current framework was introduced by automotive body SAE International in 2014 and features six levels of autonomy. These range from zero (in which a system can only issue warnings to drivers) to Level 5 (for ‘steering wheel optional’ driving in which cars drive themselves).

Most manufacturers are currently working on Level 2 (defined as ‘hands-off’), Level 3 (‘eyes off’) or Level 4 (‘mind off’). However, Toyota Research Institute boss Gill Pratt said the nuanced differences between the three levels is clouding the development race.

“It’s extremely important not to confuse the driving of levels with a gauge of where different companies are,” he said. “Level 4 autonomy depends on where you’re doing it [due to the need for cars to communicate with sensors], so you have to go a stage deeper.

“If you have a Level 4 car that has to be tested with safety personnel monitoring it constantly, then it’s not really Level 4, that’s Level 2. The hyper-focus on levels is not helpful in terms of what’s going on. The key is how many situations autonomous technology can handle.”

Pratt’s comments reflect confusion among drivers over the various levels. Tesla has introduced Level 2 features to its Model S car, but there have been a series of crashes caused by drivers not focusing on the road in readiness to regain control of their vehicle.