Trail difficulty markings, country by country.

No single system

The research for this page found no international standard for trail difficulty. Each country's markings below come from its own law, national standard or practice, and this site does not treat a colour in one country as meaning the same as that colour in another. FIS's Rule 8 and the NSAA's Point 6 both ask skiers and snowboarders to respect signs and markings; see the codes of conduct.

United States: state laws

Colorado

Colorado's statute on the duties of ski area operators (C.R.S. 33-44-107, in the text its publisher describes as current through fall 2025) requires the least difficult terrain to be signed with a green circle and the word "easiest", intermediate terrain with a blue square and "more difficult", and the most difficult terrain with a black diamond and "most difficult". Extreme terrain must be signed at its usual access with two black diamonds containing the letters "E" and "X" and the words "extreme terrain", and designated freestyle terrain with an orange oval (33-44-107(2)(d)).

The closed-trail sign is an octagon with a red border and white interior, showing a black skier silhouette crossed by a diagonal band, with "Closed" beneath it (33-44-107(2)(e)). A difficulty sign is required at or near the start of each trail, except for easiest trails that can be seen in full before starting, and lifts that serve only harder terrain need a warning where people load (33-44-107(3) and (5)).

Arizona

Arizona's statute on posting ski information signs (A.R.S. 5-703) requires a sign at each base-area lift explaining the green circle ("easier"), the blue square ("more difficult"), the black diamond ("most difficult") and the closed symbol.

The two laws disagree on one word: Colorado's green-circle sign reads "easiest" and Arizona's reads "easier". Other states were not researched.

The NSAA and 1968: not settled

Wikipedia and a resort-industry blog say the green circle, blue square and black diamond were adopted by the National Ski Areas Association (NSAA) in 1968, and the blog and other secondary pages tie the symbols to research for a Disney ski resort that was never built. No NSAA page or document saying so was found, so the 1968 date and the Disney link are both unconfirmed.

Even the NSAA's own founding year differs between sources: the NSAA's About page says it was established in 1962, while the ISHA timeline lists 1963. This site uses the NSAA's 1962.

Gradients

Wikipedia gives gradient ranges often quoted for North America (green 6% to 25%, blue 25% to 40%, black 40% and up) and says a trail is rated by its hardest part. It calls these rules of thumb. No law or NSAA document setting gradients was found, so they are not an official standard.

France: a national standard and the mayor's powers

In a written answer published on 15 May 2012 to a parliamentary question of 14 August 2007, the French Ministry of Sports said the AFNOR standard NF S 52-102 sets the rules for marking, signage and information on ski runs, harmonising them nationally with pictograms, and that NF S 52-100 covers alpine ski runs, including opening, closing and securing them.

The same answer says these standards are voluntary but are often written into municipal orders (arretes), which then make them compulsory locally. It adds that the mayor holds police powers over safety in the commune, including its ski areas, that those powers cannot be delegated, and that breaching a mayor's police order is a criminal offence.

One such order, from the commune of L'Argentiere-La Bessee (A2022-12-07, sent to the prefecture on 9 December 2022), cites NF S 52-102 of July 2001. It classes alpine runs as easy (green), medium difficulty (blue), difficult (red) and very difficult (black), and says any route that is not marked is not a ski run but off-piste. The copy read is hosted on a ski area's website and is used here only for the text of the mayor's order.

Cross-country trails have their own standard, NF S 52-103, per AFNOR's shop listing. A Savoie department paper, seen only as a search summary, says it gives a green, blue, red and black scale without numeric criteria; that is unconfirmed.

Austria, Germany and Switzerland

Austrian Standards lists ONORM S 4611, current edition 1 August 2016, "Signs for use in organised skiing areas: requirements, design and classification", as the basis for classifying difficulty and for marking in organised ski areas. Earlier editions (1999 and 2003) were titled "Ski runs: classification and basic signs". The colour scheme itself was not shown in the listing.

Sources disagree on the standard's number: Wikipedia names the Austrian standard ONORM S 4610, while Austrian Standards lists the signage and classification standard as ONORM S 4611.

According to Wikipedia, European ski areas commonly use blue, red and black, with green for beginner runs in some countries; blue usually does not exceed 25% and red 40%; and the German Ski Association's colours were taken into the German standard DIN 32912 and an Austrian ONORM. The DIN text was not seen, so this is unconfirmed.

Switzerland's guidelines from SKUS, the Swiss commission for snow-sport runs, were not found. Gradient figures on Austrian question-and-answer sites are not official and are not used.

Elsewhere

Wikipedia says Scandinavian areas use a green circle, blue square, red rectangle and black diamond with stated angle limits, and that Japanese areas mostly use green, red and black. No national body's source was found for either. Canada, Italy, Australia and New Zealand were not researched.

The story of how trail signs developed is on safety history.