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 |
Pennsylvania Tioga County |
|
| Speed Limit 65 | Speed Limit 70 | ||
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 |
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| 6.4 | Exit 6 Presho |
Formerly exit 1 | |
| 8.2 | Exit 8 Erwin Addison |
Formerly exit 2 | |
| 9.6 | Parking Area | ||
| 11.1 | Exit 11 Gang Mills Painted Post |
Exit 11 Gang Mills |
Formerly exit 3 |
| 12.1 | Exit 12 Robert Dann Drive |
Exit formerly not numbered. Accessible only from I-86 westbound. Formerly exit 3 for NY 417 and Gang Mills (both directions), prior to the reconstruction of the I-86 interchange. |
|
| 12.6 | Exits 13A-B East To  Corning Binghamton |
Formerly exits 4A-B Riverside Downtown Corning |
|
| 12.6 | Exit 12 West Jamestown Rochester |
 |
Exit formerly not numbered. |
| Speed Limit 65 | |||
| Steuben County | |||