First, we need to understand what OBD is, or on-board diagnostics. This is the ability of a vehicle to self-diagnose and report automotive data. As quite a lot of other nice things, OBD systems started to be widely adopted thanks to California. Initially, it was planned to use them for controlling annual emissions, but lack of standardisation hindered the first attempts. Thankfully, this didn't put an end to OBD systems development as manufacturers and repair technicians use them to check vehicle systems. Also, later attempts to control emissions with the help of OBD systems were successful.