To give travelers in Europe a better overview of coronavirus infections and restrictions, the European Union has introduced a traffic light system with color-coded zones based on risk levels: Green, yellow and red.

There is also a gray zone for regions where there is insufficient data.

How is each region assigned a traffic light?

The rate of new infections, or incidence, per 100,000 inhabitants in the previous 14 days and the rate of positive COVID-19 tests decide which color is attributed to a given region.

• Green is for regions reporting less than 25 new infections per 100,000 inhabitants, and test positivity is below 4%
• Orange is for regions reporting less than 50 new infections, and test positivity is over 4% —  or the incidence is between 25 and 150 and test positivity is below 4%
• Red is for regions with more than 50 new infections per 100,000 incidents, and test positivity is over 4% — or the incidence is over 150 per 100,000 in the past 14 days

Where is the information updated?

The European Center for Disease Prevention and Control (ECDC) in Stockholm on Friday will publish a map of the EU on its website that highlights which color is designated to a given region.

The site already offers an overview of the travel regulations for each of the EU's 27 member states.

So far, each EU member state has determined risk zones according to its own discretion.  European Commission President Ursula von der Leyen said this approach created a patchwork that was difficult to decipher.

"It's hard to know where you can travel, what rules you need to follow when you get there, and what rules apply when you get home," she said.

"We have to coordinate these measures to make life easier for Europeans."

Germany's top institute for infectious diseases, the Robert Koch Institute, which has been instrumental in determining the German government's coronavirus policy, will adjust its measures for declaring regions as risk zones.

So far, the agency has been using 50 new infections per 100,000 inhabitants in the past seven days as its benchmark so far — and not the now-prescribed 14 days.

Lithuania, for its part, would need to change its benchmark from 25 new infections per 100,000 inhabitants to 50 new infections.

Criticism over new traffic light system

Luxembourg's Minister of Foreign and European Affairs Jean Asselborn criticized the figure of 50 per 100,000 inhabitants, saying this was a German invention and that it was simply what Germany's health authorities could deal with when tracing the chains of infection within the country.

Luxembourg's top envoy said his country had introduced comprehensive testing from the very beginning and was investigating all cases and, due to the rise in confirmed cases, had therefore been declared a risk zone. The diplomat, who also heads Luxembourg's European affairs, abstained from voting on the new system after saying his country was being "punished" for large-scale testing.

Luxembourg is indeed leading Europe in testing, with over 6,000 tests per 100,000 inhabitants. Germany is well behind — with 1,300 tests. Bulgaria, where Germany has categorized only two districts as a risk area, is trailing at 380.

Germany has labeled all of Luxembourg a risk area since 25 September, the second time the country has been categorized as such since July. 

Read more: Germany extends list of cities under coronavirus clampdown

Austria's EU minister, Karoline Edtstadler, criticized the new criteria as inaccurate, noting that "most regions in Europe are red."

"We have to be able to assess the risk better and also maintain freedom of movement and goods at the same time," she added.

Austria is particularly worried that winter tourism in the Alps will suffer if new risk zones are constantly being declared.

Right now, 19 of the 27 EU states have an incidence of over 50 per 100,000 inhabitants during the past 14 days. Twelve countries have a test positivity rate of over 4%.

Germany, for its part, has an incidence of 34 and 1.4% test positivity rate — so at the time of writing it would be labeled an orange zone. But the situation is starkly different when one looks at the rates in major cities and regions in Germany, including Berlin.

The only EU state what would be categorized as "green" is Finland.

The EU's coronavirus traffic light system is, in the end, only a recommendation — meaning EU countries are not legally required to implement or enforce the system. Member states will still be able to decide whether to implement recommended measures. So, they will be able to introduce quarantine and tests for travelers if they like, but they will not be compelled to. Nor will the EU guidelines override national regulations. Therefore, in Germany, it could be that the existing regulations in various federal states are maintained as such.

Read more: Lancet coronavirus study explores risk of reinfection

Each EU state decides its own regulations

For the moment, it is also not clear whether the EU will introduce uniform rules on the length of quarantine, on whether people should wear masks, on requirements regarding distancing, on alcohol bans, on restrictions of sporting activities, school closures, and further measures. Germany's Minister of State for Europe Michael Roth, however, said this was "a first step, which of course must be followed by others."

Regardless of the traffic light system debate, EU states continued to impose their own new restrictions this week. Schools were closed down in the Czech Republic, for instance, and the Netherlands announced a ban on the sale of alcohol in the evening and closed down bars and restaurants across the country.

German Chancellor Angela Merkel, addressing the Council of Regions in Brussels via video link, cautioned against another lockdown. "We have to show that we have learned our lesson."

"We have to ask the people of Europe to be careful, to follow the rules, to keep their distance, to cover their mouths and noses and to do what they can to contain the virus while still maintaining economic activity."