When the whole country rush to something and this country is the only country rush this thing in the world, bad things happen. High speed rail is a good example:
It's not a mature, settled technology;
other countries are still cautions: there are some commercial operations, but not in a scale close to China;
You can buy good trains/cars, you can even build good rails, but the whole system is way more than just trains and rails.
动车追尾事故真相:铁道部再次慌了神