Ras,
There are no "certified" markings but all JUTA, JCal and Maxi drivers are certified. Do not take public transportation (route taxis) as they are all NOT certified.
It is enforced mainly at roadblocks and speed traps, but we have seen the occasional vehicle get pulled over.
Sheffield is in the Corridor, but you can't visit private homes, only businesses in the area.
See you soon!