Part of the filming used extras in their own vehicles to, I assume, fill out the look of a highway chase sequence that closed down the freeway for driving stunt sequences. Filming at the location was cancelled (or at least the use of extras) for Thursday but I am not sure if that is due to the injury or because of the filming in Chicago. Further details have not been released but hopefully the extra will make a full recovery.
Relating to the Indiana filming, below are two videos posted today that show a little bit of the action. Optimus Prime has taken on a blue color for I assume special effects reasons as that shape will be replaced by CGI in post-production. It must be a complicated sequence as that hasn't been necessary in the past. Thanks to DJ Bigtyme Beats for the videos.