English Idiom: Open a can of worms
The idiom open a can of worms is used to describe a situation that has become more complicated once you start to deal with it.
It is similar to the domino effect. Once you start to deal with one problem, you discover another issue that you have to deal with, and then there is another and another and yet another.
For this reason, many politicians refuse to address a situation because they know they will be opening a can of worms.
In Japan, we could say that attempting to solve the issue of elderly drivers is opening a can of worms.
Making the decision to test elderly drivers every year will create a conundrum and require a lot of time and money.
As more and more elderly drivers are forced or asked to give up their licenses, governments and family members will have to provide transportation for shopping and hospital visits.
This will increase the need for family members to take days off work to help their elders.
Companies will have to be compensated for time lost and so on.
Seriously trying to deal with the issue of elderly drivers in Japan would be like opening a can of worms.