It's a good milestone day for Android's side-projects and apps. Earlier we reported that the Android Wear app had reached 10 million downloads on the Play Store and now we're seeing the same number for the Android Auto app.
10 million downloads since March of 2015 is a nice number, especially considering that the app is geo-restricted and you either have to be aware that it works on phones without needing a compatible car or have to have purchased a new compatible car or heads-up unit in the past 2 years or so to know about it. By comparison, the Android Wear app has been available for about 3 and half years, is available worldwide, and the cost of entry is much lower (if you don't take into account those who use the Auto app as standalone).
Auto has been ramping up pretty quickly too. According to AppBrain, it had 5 million downloads in June of 2017 so it only took 6 months to double that number. Hopefully that rise in adoption translates into more interest in the platform by Google (updates, new features, etc) and more third-party apps adding support for it. For now, all we can say is congrats to the Auto app team and you can check it out at the widget below or grab the latest version from APK Mirror.