There aren’t many Nordic ski routes where you can gauge your progress by mileage markers. The exception, I learned last weekend, is the Whiteface Veterans Memorial Highway.

When the state repaved the highway recently, it installed highway reference markers along the shoulder. These are the small rectangular signs on metal posts that you see along state-maintained roads every tenth or two-tenths of a mile. Usually they’re green, but those on the Whiteface highway are brown.

As I skied up the toll road (which is closed to vehicles in winter), I tried to make sense of the three rows of numbers. The top two rows did not change from sign to sign, but the last two digits in the bottom row did. As I got higher, the numbers got lower.

You can refer to these two digits to measure your distance traveled – useful to know if you ever ski or bike the highway.

On the first reference marker, next to the toll house, the bottom line reads 1153. This signifies that you are 5.3 miles from the start of the highway just below Whiteface’s summit (this is the start of the highway in officialdom, though people tend to think it ends there).

As you climb the highway, you’ll pass a marker every two-tenths of a mile on the right. On Sunday, I went only as far as the Lake Placid Turn. Just before this hairpin, I passed a marker whose bottom line reads 1115 – indicating that I was 1.5 miles from the start of the highway. In other words, I went about 3.8 miles to reach the turn.

These figures more or less comport with the mileage in Tony Goodwin’s Ski and Snowshoe Trails in the Adirondacks. Goodwin says the hairpin turn is reached at 3.5 miles and the end of the highway is reached at 5.3 miles.

You might be wondering what the other numbers stand for (or you might think what follows is too much information).

The first row (431) is easy: it’s the route number. State Route 431 extends from the top of Whiteface to the four corners in Wilmington. The toll road comprises only the first 5.3 miles.

The middle row (1201) requires a bit more explanation. The first number refers to the state Department of Transportation region. Whiteface Mountain is in Region 1. The second number refers to the county—in this case, Essex County. Within each region, the counties are numbered alphabetically. In Region 1, Essex County is second in alphabetical order, after Albany County. Hence, this row begins with 12.

The third and fourth digits in the middle row indicate how many times a highway has crossed a county line. Markers start at 01 and increase by one each time a county line is crossed (even if the road leaves and later re-enters a given county). In this case, the entire road is within Essex County, so these digits stay at 01.

In the bottom row, the first digit is a “control segment number,” which indicates the division of a route within a county. The divisions are usually demarcated by city boundaries. The first digit starts at 1 and increases with each division crossing. In the case of the toll road, there are no such divisions, so the number stays at 1.

The last three digits in the bottom line of a reference marker refer to mileage from the start of the segment. But there is a problem. The last three digits on the marker near the toll house are 153. This would seem to indicate that the distance is 15.3 miles, but we know the actual distance is only 5.3 miles. So why aren’t the digits 053?

We turned to Bryan Viggiani, a DOT spokesman, for an answer. Skiers and bikers, as it turns out, can ignore the 1 before the 53. In all the toll-road markers, this 1 was inserted merely to distinguish them from the reference markers on Route 431 below the toll house. Without the 1, the toll-road markers would duplicate markers below the toll house, which were erected long ago. The bottom picture shows the first marker below the toll house, with a distance of 000.

This brings us to the purpose of these markers. Federal law requires them so that officials can keep track of how often accidents occur in a given location. The goal is to make the roads safer. Once a marker is established, it is rarely changed, even if the route number is changed. Rather than update all the markers on Route 431, DOT improvised by adding an extraneous digit to the markers on the toll road.

“It’s easier to match up the historical data if they keep the numbers the same,” Viggiani said.

He said DOT also uses the reference markers to catalog the locations of culverts, guide rails, and other highway infrastructure.

A few last points: the reference markers on the right side of the toll road as you climb indicate the mileage in odd tenths of a mile: 5.3, 5.1, 4.9, and so forth. These face downhill. On the opposite side of the road there are markers indicating the mileage in even tenths of a mile. These face uphill. Thus, there are markers every tenth of a mile, but they alternate from one side of the road to the other. Finally, DOT notes that markers may not be spaced exactly a tenth (or two tenths) of a mile apart, due to a variety of considerations. However, they come very close. The next time you ski the highway – assuming we get snow again – you can count on them.

If you haven’t got your fill of reference markers, check out the Empire State Roads website.