If you can't legally cross a double yellow line why is it ok when entering or exiting a business?

Again, corporate america rules.

You can cross it but not drive on the other side parallel to it. In my state you can make a "U" or "K" turn over it or cross it to enter a lot.

However a pair of double yellow lines with a certain minimum space between is a symbolic barrier that can never be legally crossed.

You're allowed to cross the double-yellow line to enter or exit the roadway.

The double-yellow line indicates a NO PASSING zone. You are not allowed to cross it in order to pass someone.

States do have it listed as an exemption for turning in to a driveway, I probably should have said that in the original answer. The only other choice would be to put broken lines up for every driveway in a residential zone as well as business district. Since the original question was about a carpool lane I couldn't see this exemption coming up and so didn't mention it.

what else would you need to cross it for? On the other side of that double line is on coming traffic? You only would need to cross it to enter the drive way of a business.

or side road.

Anyway, there are rules to how they determine how often and how much is considered swerving. This can get cops in trouble as they sometimes are very strict, when that is not the intent of the law, or they lie, especially because they want to pull young drivers over, or people over at night.

Cause people fudge the rules all the time, and I doubt a cop would care about that.