In PA, PennDOT has a website; however, you must be a member to access.
In lieu of that, PAPA-Pennsylvania Asphalt and Pavement Association also lists the Asphalt Index. Maryland has the Maryland Asphalt Association.
I would suspect that googling "your state" Asphalt Association would work. Also, your favorite paving contractor or site contracotr would know. Call them. With the volatility of asphalt, they are keenly aware of the index and its trends----none!