Short distance roads that are an extension of a longer road

[Alps]

RI 15 has about a quarter of a mile in Massachusetts, as MA 15 (unsigned).

what was the number of this when MA-15 was an active route?  (now I-84)

I don't think Massachusetts signs 15, so it was probably just unnumbered.

I wouldn't be surprised if there's at least one street sign reading "Route 15," though I can't recall one.  It's still a commonly used name locally.

The signs there basically refer to RI 15.

[Roadsguy]

NJ 413 in Burlington is a short extension (from PA to US 130) of the longer PA 413 on the Bristol side of the Burlington-Bristol Bridge.

[31E]

TN 99 from I-65 to US 431 is a direct extension of US 412. Similarly, TN 69 from I-40 to US 412 is a direct extension of US 641. KY 79 is only 1-2 miles away from being a direct extension of US 79, and since it goes in the same direction I'd say it's an indirect extension. KY 79 is 104 miles long, so it's not short distance, but it is much shorter than US 79.

[hbelkins]

TN 99 from I-65 to US 431 is a direct extension of US 412.

Not really. TN 99 was there long before US 412 came along, and is actually the hidden state route number for 412 between Hohenwald and I-65.

[Jim]

Many of New York's 3DI's continue as state routes with the same number beyond the end of their Interstate designations.  For example, both Capital Region 3DI's do this: I-890/NY 890 and I-787/NY 787.

[amroad17]

^As well as Syracuse's I-690/NY 690, I-481/NY 481, and Rochester's I-390/NY 390, I-590/NY 590.