Rt 15 from Williamsport,PA to Corning, Ny

Rt 15 from I-80 to Corning is practically an interstate. Most of it is 4 lane divided highway with speed limits as high as 65 mph. I would recommend that you take I-180 from I-80 up to Williamport instead of Rte 15 form I-80. By the title of your post you probably already figured that out.
The piece of 15 that crosses the state line wasn't finished the last time I was thru there in January. It's just two lanes for a few miles and then widens back out.

We haven't been in NY for several years but at that time fuel prices at the Indian Reservation stations were very favorable since they were not charging the state fuel taxes to any customers.

Thanks Tom for your prompt reply! We are heading to the finger lakes and didnt want to ruin a good trip with unexpected issues. We traveled rt 86 across newt irk last year and the road was very very rough. We decided to try a new route but were unfamiliar with rt 15.

I used this route 2 or 3 times. It's a surprisingly very good route. Most is a new 4 lane with limited access. Not many grades. No tunnels or low clearances. Buy gas before entering NY. I fueled up in Lawrenceville, PA.

-Tom