Reference marker (New York)

In New York, a reference marker is a small green sign mounted approximately every one-tenth mile on highways maintained by the New York State Department of Transportation. This was initiated in response to the Highway Safety Act of 1966 enacted by Congress, in an effort to monitor traffic and identify high-accident locations. New York's system inventories and indexes all touring and reference routes, in addition to service and rest areas, ramps, and reservation roads.

New York's system is similar to California's postmile system in maintaining the state's highways and route logs. The New York State Thruway Authority adopted its own reference system for the New York State Thruway system, including I-287 and I-84. There is a similar reference marker system in use in neighboring Vermont.

The reference markers (popularly referred to as "little green signs", or "tenth-mile markers") are green signs that measure 200 millimeters (8 in) wide by 252 millimeters (10 in) high and are placed every 528 feet (161 m) on state roads, freeways, and parkways. There are three rows of white numbers.

The top row indicates the route number. The letter "I" is used as a suffix for an Interstate highway, but may instead be a prefix on some markers. If a route is re-numbered, it will retain its old route marker (such as the Watervliet segment of NY 2, which was formerly NY 7 until the mid-1980s). If a route number does not use all four digit spaces, there will be blank areas.

When two or more routes run concurrent or overlap, typically only the lower number highway will be present, or in some cases, a higher level highway's number (such as "88I" appearing on markers where NY 28 overlaps Interstate 88 near Oneonta).

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