There are vans that are required to take you across if the gates are
closed. Last year while out on a ride they closed the walkway due to
falling ice. I asked a cop what to do and he directed me to the
vans. On the NJ side you will need to navigate to the toll area, and
you will see a buss shelter. They come pretty frequently, and you
will have to stand in the aisle with your bike. If the walkway is
closed they cannot refuse you.