Comment by wongarsu

Like this: https://c8.alamy.com/compde/t0580m/der-verkehr-kurve-spiegel...

Or this: https://cdn-01-artemis.media-brady.com/Assets/ImageRoot/DMEU...

Reasonably common in difficult corners in Germany and Austria. Probably elsewhere too.

The downside is that it's road infrastructure that has to be installed. The upside is that it works for everyone, including people in 20 year old cars or on bicycles.