Crit'Air: France's clean-air sticker

Its official name is «certificat qualité de l'air», an air-quality certificate. It places a vehicle in one of six classes, from 0 to 5, each with its own colour. The lower the number, the cleaner the vehicle is considered to be. Very old vehicles drop out altogether: they get no sticker and count as unclassified, which in practice means they are the first to be kept out wherever restrictions apply.

Besides the class, the sticker carries the vehicle's registration number. That ties it to exactly this car with exactly this plate. Stuck on a different car, or on a car that has since been given a different plate, it proves nothing. It goes on the front windscreen where it can be read from outside; a sticker in the glovebox does not count.

The sticker is neither a toll nor a tax. It is a label on the basis of which cities and authorities decide which vehicles may enter an area and when. How it is checked — by police and municipal officers when you stop or park, or automatically — varies from place to place and keeps changing. Assume you will be checked, not that it will happen to someone else.

Three details decide the class: the type of vehicle — passenger car, van, motorcycle or heavy vehicle — the type of drive, and the Euro emissions standard the vehicle was approved to. If the standard is missing from the papers, the date of first registration takes its place, because it shows which standard was at least required at that point.

For passenger cars this produces a ladder that is easy to remember:

At the same standard, a diesel lands one class lower than a petrol car; a Euro 6 diesel shares class 2 with a Euro 4 petrol car. And a hybrid without a plug is classified by fuel and standard like any other combustion car; only the plug-in hybrid gets class 1 on account of its drive alone.

The official source offers a calculator that works out the class from vehicle type, drive and standard or first registration. If you are about to buy a car and plan to take it to France later, you can check before buying where it will land — a difference you notice more in daily use than in the price.

France attaches two kinds of restriction to the sticker. The first are the permanent low-emission zones, the «zones à faibles émissions» or ZFE for short, set up by urban areas; the best known are in Greater Paris and Lyon. Inside such a zone, vehicles of certain classes may not drive at certain times. Which classes are excluded, how far the zone reaches and whether the ban applies round the clock or only on weekdays is set by each zone for itself.

The second kind are restrictions during high air pollution. When a pollution episode is declared in an area, the prefecture can order «circulation différenciée» for its duration: only vehicles of certain classes may then drive, even where there is no permanent zone. Such orders are announced at short notice, often the day before, and catch out travellers who know nothing about them.

The zones are politically contested in France. Parliament voted to abolish them, the Constitutional Council struck that part of the law down on procedural grounds, and the zones remain in place. Hardly anyone believes the argument is over. For you that leads to one simple rule: rely neither on a newspaper article nor on what applied a year ago, but check the website of the city or metropolitan authority whose area you will cross before you set off.

A zone is signposted at its entrance, with additional panels showing the classes and times concerned. Satnavs do not know the zones reliably, and by the time you see the sign it is usually too late to turn round.

The sticker is issued by one place only: the French government's website for the «certificat qualité de l'air», run on behalf of the environment ministry. Its address ends in «.gouv.fr». You order there online, from abroad too, and the sticker arrives by post. The price is low.

Search for “buy Crit'Air” and other sites often come up first. They look official, charge many times the price and at best simply pass your application on; at worst nothing ever arrives and your vehicle papers sit with a stranger. There is no reason to pay an intermediary: the official form is short.

To order you need the registration number, the country of registration and a file of the registration document that shows the vehicle's details. Make sure it is legible and includes the page with the technical data. An unreadable copy holds up processing, and that is exactly the time you will be short of before you leave.

Because the sticker comes by post, planning is the real issue. Delivery abroad takes longer than within France, and if you order in the week before you leave you may set off without it. Do not count on an order confirmation standing in for the sticker on the windscreen; order early enough for it to be in place before you go.

The restrictions apply to all vehicles, wherever they are registered. Foreign plates do not exempt you from the sticker, and another country's environmental sticker is not recognised: the German green sticker means nothing to a French officer, and Crit'Air in turn is not valid in German low-emission zones.

The most common trap is in the papers. Many foreign registration documents do not state the Euro standard in plain words, but as a code or not at all. The harmonised EU registration certificate has field V.9 for it, but whether it is filled in depends on the country and on the age of the document. Without the standard, the class is set from the date of first registration — which can give a worse class than the car deserves, for example with vehicles that met a standard before it became mandatory.

The certificate of conformity, the COC, states the standard reliably. Keep it to hand and check while filling in the form whether it accepts additional evidence of this kind. If the class on the sticker you receive does not match what the papers show, contact the issuing body before you drive into a zone with the wrong class.

This is not only about cars. Motorcycles, motorhomes and vans need the sticker too and are classified according to tables of their own.

In France the registration number stays with the vehicle, even when it changes hands. A sticker on a used car's windscreen therefore matches it as long as it runs on that plate. If the car makes the journey home on different plates, such as temporary transfer or export plates, the sticker proves nothing any more: it shows a number that is no longer on the car.

Ordering a new sticker for a plate that only exists on collection day practically never works in time, because of the post. The clean solution is therefore not the sticker but the route: if the pick-up address lies inside a zone, agree with the seller to hand over outside it, and plan the drive home on roads that do not touch a zone. The day before, check whether a pollution episode has been announced for the region.

It pays to know the class before you buy, even if the car will not stay in France. Ask for a photo of the registration certificate and look for field V.9 — on French papers it is usually filled in. That way you know what you are buying and have the detail to hand when you later order a sticker for your own plate.

Once the car is registered at home, every later trip into a French zone works as it does for any foreign vehicle. The sticker is issued for the new plate, and the old one comes off the windscreen — at a check it only causes confusion.