The interstate indicates your ability to go from one phase of your life to another. It could also indicate the different steps you are taking and how you are managing to make it go smoothly. The dream could either indicate the situations that already happened, the current situation or unknowingness in the future. If you are stuck in the interstate, it means that you are trying to figure out which way to go. If accidently you went of the interstate, you have to become more cautious if you wish to achieve your target. If someone went on your way, you should reconsider the people you are communicating with or the situations youve got yourself into, otherwise you wont be able to get what you want.
Dream dictionary: Interstate dream meanings
To better understand this dream, read also the interpretations of highway.