The USA EPA requirements do go a bit overboard but at least they are trying to make this a cleaner Planet!
Nice detailed diagram of how the complex system works.
Here in South Africa there are no Roadworthy checks required at all until a new Buyer needs to put the vehicle in his own name!
My 2002 2.5 Export Diesel I bought new in May 2002....I do look after it and would take action if it started to below smoke or if the brakes or tires were in bad shape but some of the vehicles on the road here belch out smoke, have worn out tires and are held together with fencing wire....no problem until someone wants to buy it!
So I personally would like to see more stringent Roadworthy and Emissions controls to be applied but this is Africa and things work differently here!