I was looking at Knoten Kaisermühlen (as you do), and spotted that there appears to be a second route through it, from the A23 NE to the A22 NW. The official route is 270° clockwise round the tight inner slip road, third exit, but instead it seems to be possible to leave at the second exit, go 180° anti-clockwise round the big loop under the A23, then cross over and turn 90° round onto the A22, which happens to be under the new U2 bridge, and where OpenStreetMap currently has the caption 'Donaustadtbrüke'.
However, if one zooms in on the cross over point, it seems that there's a solid white line marked all the way along, to prevent you doing that. Spoilsports
Incidental question - OpenStreetMap shows that the S1 is now open all the way round to Brünner Bundestraße, whereas Google Maps thinks that only the first bit (the S2) is open. Which is right? Given that Google gave driving directions along the A6 before it was open, my money would be on OpenStreetMap.