This picture shows the Hallerbach Valley Bridge and its 4% grade. The curve in background has a radius of 2.17 miles.
In order to reduce tunnel and bridge mileage, the 186 mph line from Köln to Frankfurt has been built steep and curvy: Up to 4% of grade, down to 2.08 miles of curve radius, up to 6.7 inches of superelevation. By German regulations, the unbalanced superelevation limit for normal, non-tilting trains is 5.9 inches.
© DB ProjektBau GmbH / Lothar Mantel, used with permission.