I rcvd a speeding ticket for 70 in a 45 construction zone. Can I introduce evidence from I-Pass showing my avg speed was 48?

To be admissible in Illinois, evidence must be relevant. You can certainly try to introduce the evidence, but the prosecution will likely object (or the court will object for them in the interests of expediency) based on the fact your evidence doesn't prove or disprove anything specifically. The evidence simply shows that your average speed between two points was 48 mph.... it does not go to the "heart" of the matter, which is whether you were exceeding the speed limit at the time the officer clocked your speed.

Even if you did get the evidence admitted, it likely would not be considered very probative by the judge for the same reasons. When defending yourself, remember to focus on the specific issue at hand: "were you exceeding the speed limit in the manner described and in the location described by the officer as written on your traffic ticket?"

Good luck!

NOTE: This answer is not intended to be legal advice and should not be construed in that way. This answer does not create an attorney-client relationship and no such relationship may be created absent a signed retainer agreement. The author is licensed in Illinois only, and his answer is for educational purposes alone.