Self-driving car manufacturers, such as Tesla, Google, Volkswagen Group, Mercedes-Benz, Nissan, Delphi, and Bosch submitted their first disengagement reports to California's Department of Motor Vehicles, and the results are as expected from a complicated technology.

To test self-driving cars on the roads of California, ARS Technica wrote that companies should submit to the DMV a disengagement report, which records the incidents when a human driver has taken over for the autonomous car. Google's results show that out of the 424,000 miles its autonomous car has driven, it recorded 341 significant disengagement incidents. Meanwhile Nissan experienced 106 disengagements out of the 1,485 miles on the road, Delphi had 405 out of the 16,662 miles, and Tesla reported zero disengagements.

According to eWeek, Google classifies disengagements into two types. One if the immediate manual control, and the other is when the driver proactively takes over. The first category is when the self-driving car's software detects failure and automatically gives the control to the human driver. Meanwhile, the second type of disengagement is when the driver proactively decides to take the control due to safety doubts.

Google reported a drop in disengagement rates in the duration of the test. Its disengagement dropped to only one per 5,318 last November 2015, from one in every 785 miles in the same time period in 2014.

However, Fast Company points out that conclusions on reliability shouldn't be made out of the disengagement rates in these tests. The results are only limited to California public roads. There are still countless tests being done in other states.

Reports from the DMV don't emphasize the improvements in the disengagement rates. The reports are also a little misleading since it don't really put into account the two categories of disengagement that Google has established. California DMV only asked for the report on incidents when drivers were justified in taking over the self-driving cars.