How do states use OBD II for emission inspections?

Many states connect a computer directly to a vehicle's OBD II system. The inspector can then read "faults." In some states, this type of inspection has replaced the tailpipe emission test.
See also:
Introduction
City Safety™1 is a support system designed to help the driver avoid low speed
collisions when driving in slow-moving, stop-and-go traffic.
City Safety™ is not active if your vehicle’s speed is belo ...
Channel lock
Access to specific channels can be restricted (locked). A locked channel will
not provide audio, song titles, or artist information.
NOTE
All channels are initially unlocked.
Locking a chann ...
Active Bending Lights (ABL)*
Headlight pattern with the Active Bending Light function deactivated
(left) and activated (right)
When this function is activated, the headlight beams adjust laterally to help
light up a curve ...
