They will have open pits so that anyone who wants to go to the pits can go down. (usually before the opening ceremonies) The pits are normally open for 45 minutes to an hour depending on their schedule. So, you do not need to get a pit pass.
The tunnel that goes under the track from the grandstands to the pits is not convenient. I'm 6' 1" tall and I have to duck down in quite a few places. My wife is 5" 8" tall and she has no problems with the low ceiling height of the tunnel. The floor drops down and raises in a number of places, so you need to watch your step. Plus the tunnel is only about 6' wide with a cabling trough along one wall, so there's only about 5' of usable space in there for two way traffic There is also a tunnel under turn one. It's easier to get through but it's a longer walk. It probably takes about the same amount of time either way. It probably takes 3 to 5 minutes to get through the tunnel. So, If you have open pits for 45 minutes, you lose about 6 to 10 minutes of that going back and forth through the tunnel.
Make sure to bring a camera down to the pits. I like to take pictures of the riders and the mechanics in action plus all of the different bikes.
