Grades come from the corner's tightest radius. Hairpins (over 135° and very tight) are called as "hairpin".
How many seconds before a corner the note is read, at your current speed. Never less than 60 m.
The recorded Northern English co-driver is the default and works offline once loaded. The phone voices are a backup; iOS only shares its basic voices with web apps, so downloaded Premium voices won't appear here.
You only have standard voices right now. Download a Premium voice as described above.
Simulate drives the route on its own, slowing for corners, so you can hear the calls before a real drive.
Keep this screen open while driving: Safari stops location updates when the page is in the background. Add it to your Home Screen (Share → Add to Home Screen) for a full-screen app. Turn the ringer switch off silent mode if you hear nothing.