Travel restrictions put in place by countries amid the ongoing COVID-19 pandemic are making new track preparations "quite difficult" for Formula 1 teams, according to Mercedes' Andrew Shovlin.
The next four F1 races are all set to take place on circuits that were not originally due to feature on the 2020 calendar, and none of which have hosted a grand prix in the last seven years.
Next weekend's Eifel Grand Prix will be held at the Nurburgring, which last staged an F1 race in 2013.
This will be followed by back-to-back races at Algarve, hosting its first grand prix, and Imola, which has been absent from the calendar since 2006.
F1 will then return to Istanbul Park in Turkey in mid-November, marking the track's first race since 2011.
Having already agreed to not hold private testing running at any of these tracks in a bid to cut costs, teams are relying on simulator work to get up to speed with the circuits.
But with the UK imposing quarantine requirements for an increasing number of countries in a bid to curb the spread of the virus, teams are finding it more and more difficult to get drivers in to complete the simulator days as normal.
"We've got a bit of a backlog of new circuits this year," said Mercedes track engineering director Shovlin.
"You normally you deal with one or two. There's an awful lot of additional work that you do with those new tracks. And ideally, you'll get the drivers there to drive the simulator.
"But that's getting increasingly hard with all the restrictions on COVID, because the exemptions only apply to a race weekend. You're not exempt just because you're in F1 - it's only specifically for the race events.
"It's proving quite difficult to keep on top of all these new tracks coming."
All F1 team personnel have exemption from quarantine guidelines following races, but this does not apply outside of grand prix weekends.
Mercedes typically works with reserves Stoffel Vandoorne and Esteban Gutierrez to complete its simulator work in tandem with race drivers Lewis Hamilton and Valtteri Bottas.
But Shovlin said the same approach remained in place when tackling the race weekend from a set-up point of view.
"The actual normal work of selecting how you run the car and everything well, that's the same wherever you go," Shovlin said.
"Whether it's a well known circuit or not, it's more elements, understanding where we think the tyres are going to be.
"So the pre-event work is a bit harder from that point of view. Ordinarily, we would have had the drivers in for the simulator to practice."
Shovlin also acknowledged that the weather at the Nurburgring could be a "big unknown", with the race taking place in mid-October and single-digit temperatures forecast.
"The other big unknown is just what the weather is going to be doing," Shovlin said.
"It could obviously be quite a wide window. And that might make it interesting.
"It's a good circuit, it'll be nice to go back there."