If/when he arrives or If/when he will arrive

If they are correct, do the following pairs of sentences mean the same thing?

PAIR 1:

1) With the icy roads and traffic, I don't know when he arrives.

2) With the icy roads and traffic, I don't know when he will arrive.


PAIR 2:

1) I don't know if he arrives before dark.

2) I don't know if he will arrive before dark.

Thank you