How much gas evaporates in hot sun in unshaded parking?
The newer vehicles of today have evaporative recovery systems installed in them. If they malfunction, the check engine light comes on to warn the owner. The manufacturer has even put a test port into the system to be used to trouble shoot malfunctions. If you think of it that way, I think the EPA is serious about emission control. If you want to challenge this, just leave your gas cap off when you fill up and you will see that check engine light in no time. Once you start driving the system checks it’s self and if it sees a problem, you get a light.