To use the Swiss motorway, you need to buy a “vignette” sticker every year which is actually valid for 14 months (for example, the 2020 vignette can be used from December 1st 2019 until end of January 2021).
It costs approximately 40CHF, and it is much better to take it even just for one day, they are specially checking foreigners cars (the fine is 200CHF).
You can buy it at the Bardonnex toll but it can be hectic. Or at the Automobile Club du Mont Blanc (between Bonlieu and Préfecture in Annecy) for 40€, they can also mail to you.
AUTOMOBILE CLUB DU MONT-BLANC – 15 rue de la Préfecture – 74000 ANNECY
Tel : 04 50 45 09 1204 50 45 09 12 – firstname.lastname@example.org
You can also buy it at some places on the French motorway, it is convenient and available all year on the motorway shop “La Ripaille” (Aix les Bains/Annecy).
Be careful, in Switzerland, the motorway signs are green and the road one is blue (opposite than French).
The average speed limit is 120km/h (from Bardonnex toll to the airport it is 100km/h). Be aware that they do have a lot of speed cameras.
Just before reaching Bardonnex toll (the most important one coming from French motorway) and leaving France, you will have a speed camera (50km/h), I call it the “slot machine”, it is one of the most “successful” speed camera in France. But not a good way to remember leaving our country! Swiss police are also very strict so be careful during your stay there!
If you are only driving to Geneva airport from Annecy, you do not have to use the Swiss motorway, just much faster and easier, or else you can use Perly toll for example and stay on the city roads but you will need a good navigation system.