Legal distance between street & helipad

There's a facility locally where all employees enter the rear parking
lot via a private drive. The drive is located 25 yards from the
helipad, and it goes BY the helipad, but does not connect to it.

When a helicopter is landing, parked, or taking off, the drive is
closed off to thru traffic.

I was just wondering whether there are laws regarding how closer or
far active traffic must be from an in-use helipad, and if not, how
close a vehicle would have to be to a moving helicopter to either a)
be affected, or b) affect the helicopter.