The Wall Street Journal has a report on all the states, including Indiana, that have raised speed limits recently. Officials are finally starting to realize that there is a "flow of traffic" speed that the law has to acknowledge:
But lawmakers in Texas, Michigan and other states say that raising speed limits will make roads safer by restoring credibility to speed-limit signs and making driving speeds more uniform. While transportation engineers acknowledge that raising speed limits hurts fuel efficiency, they contend that careful studies of traffic flow and driver behavior show that many speed limits are actually too low. Most drivers who exceed these low speed limits are doing it safely. "In Texas, they are already going [80 mph] anyway," says Carlos Lopez, director of traffic operations at the Texas Department of Transportation. "People are driving where they feel comfortable."
Naturally, Texas has to top everybody. It's 80-mph limit is the highest in the nation.