Most of the highways are 70. The main freeway of Indy the 465 is 55 and in some areas of downtown Indy it's 50. Be very careful they are stepping up enforcement of the speed limit here, they have a budget shortfall and figure it's a good way to get more money coming in.
I am an hour south from the Indiana/Michigan line ... Indy is right below us. Matt had his bone marrow transplant at Indy, so we drove it about every day. Takes us 2 hours and 15 minutes to get to downtown Indy.
Speed limits ... they are different depending on if you are "in a city limit". On an interstate they can vary from 70 to 55. You just have to watch the signs!!
Interstate highways are typically 70. State highways 55. The unofficial speed limit of465, the interstate loop around Indy mentioned above, is 75/80. You just try driving the posted speed limit of 55 and you'll get creamed. Cops will just drive right by you typically, even if you're doing 65.
On the way back from my parents last month we got popped doing 74 in a 55. Cops here are tricky, Laura - they now have unmarked brand new Mustangs. That's what got us, AND the guy behind us. Pulled us both over at the same time.
Oh, and they're all different colors, so I can't even tell you which ones to watch out for. At one point, I thought they were all blue with white rally stripes. But then the one that got us was burgundy. And I've also seen a gold'ish one.