Where can I find out the functional classification of a particular highway?

The functional class of a highway is used in planning, design, and management. Only certain highways are eligible for Federal Aid. In the MUTCD, there are some requirements (such as the need for chevron or arrow signs on sharp corners) that are different for arterials and collectors. These highway designations are approved by the New York State Department of Transportation (NYSDOT) and Federal Highway Administration.

The three broad classifications of highways include:

Arterials
Major roads and streets linking between or within cities
Collectors
Roads and streets that typically serve regional travel and link smaller population centers with the rural areas
Local
Roads and streets connecting businesses and farms to the smaller communities and individual homes

To find out which roads and streets are designated as arterials and collectors, there is a webpage on the NYSDOT site

Some areas are not posted yet, but a draft map can be obtained by contacting the NYSDOT.