looking for information on vehicle safety inspections

I am looking for information on vehicle safety inspections I'm looking
for information about:

1. Effectiveness of automobile safety inspections as performed by some
states.

2. Information on states that have dropped their safety inspections,
and why... (Such as Florida did in the 1970s)

3. Studies that show the effectiveness of safety inspections conducted
by:

a. State run facilities (such as was done in Florida)
b. Private facilities (such as done in many states such as Mass.)

4. Any other non-anecdotal information about automobile safety
inspections,

5. Instances (first hand, if possible) of safety stations (typically
private) cheating customers, Usually done to older, women, and
non-sophisticated customers, where unnecessary repairs are performed.

6. Allowing 'unsafe' vehicles to pass (usually for a friend, or for
'under the counter' payment to the inspector.) and any other
irregularity in safety inspections.