I-99/US 15 is a short route in the Southern Tier running from the Pennsylvania border to I-86 in Painted Post. US 15 was truncated to its present end in 1974; previously, it ran along NY 415 and NY 15 to end in Downtown Rochester. The process of upgrading US 15 to I-99 in New York consisted of a project reconstructing the interchange with NY 17/I-86 (including relocating the NY 417 interhcnage south and converting the former NY 417 interchange into an exit for Robert Dann Drive), filling in the freeway gap between PA 287 and Presho over two projects (with an intermediate end at Watson Creek Road), and converting to mile-based exit numbers. The NY portion of I-99 was designated in 2014. and NYSDOT internally considered the road to be solely I-99. It is unknown when or if PA will designate I-99 on its portion of the freeway to Williamsport.

Mile Northbound Southbound Notes
0.0 New York
Steuben County
Tioga County
Speed Limit 65 Speed Limit 70
I-99 north US 15 north US 15 south
6.4 Exit 6
CR 5
Formerly exit 1
8.2 Exit 8
NY 417
Formerly exit 2
9.6 Parking Area
11.1 Exit 11
NY 417
Gang Mills
Painted Post
Exit 11
NY 417
Gang Mills
Formerly exit 3
12.1 Exit 12
Robert Dann Drive
Formerly exit 3 for NY 417 and Gang Mills (both directions).
Exit formerly not numbered after construction of current interchange with I-86.
12.6 Exit 12
I-86 West NY 17 West
Exit formerly not numbered.
13.3 Exit 13A
I-86 East NY 17 East
Formerly exit 4A
Diverges at the same point as exit 13B
13.3 Exit 13B
NY 352
Downtown Corning
I-99 south US 15 south Formerly exit 4B
Diverges at the same point as exit 13A
Speed Limit 65
Steuben County