What is the statutory minimum tire tread depth (Profiltiefe) for passenger cars in Switzerland, and what tread depth is recommended for safety in wet/winter conditions?

1. Legal minimum is 0.5 mm; recommended is 1.0 mm
2. Legal minimum is 3.0 mm; recommended is 8.0 mm
3. Legal minimum is 1.6 mm across the entire tread surface; recommended is at least 3.0 mm for summer tires and 4.0 mm for winter tires
4. There is no legal minimum tread depth in summer