Browns are mad buggers, so give them an especially wide berth if you see one. Tigers have dreadful eyesight, so you're likely to be well past before they even see you to have a go, plus they're more likely to piss off into the grass. Both can be pretty bad news if you get chomped, because the venom is potent and fairly rapidly-acting, but can be slowed if you remain immobile. Brown bites can be difficult to treat even with the correct antivenene because there is some chemical trickery in the venom that resists treatment.
Blacks & Copperheads may also be found, but will pose less of a risk. They tend to be fairly placid, especially Copperheads, plus their venom is relatively low on the toxicity scale. Copperheads rarely bite, even if you stand on them and stay there; instead they will just headbutt you to try to make you get off them!
Of course, as others have said treat them all with respect, give them a wide berth if possible & try not to get between them & shelter.
