The “National Cycling Plan 2020 – Joining forces to evolve cycling” guides and informs the development of cycling across Germany:

http://edoc.difu.de/edoc.php?id=1U032RD6

However, most initiatives are drawn up at a regional and local level. The cities of Münster, Kiel and Freiburg have become trendsetters, while large cities like Munich or Berlin are quickly catching up in terms of quality of infrastructure and share of cyclists:

http://www.stadtentwicklung.berlin.de/verkehr/politik_planung/rad/strategie/download/radverkehrsstrategie_senatsbeschluss_en.pdf

Cycling is a focus area of the transport development strategy in Leipzig: Cycling development strategy 2010 – 2020 for the City of Leipzig (German language only).

https://static.leipzig.de/fileadmin/mediendatenbank/leipzig-de/Stadt/02.6_Dez6_Stadtentwicklung_Bau/66_Verkehrs_und_Tiefbauamt/radverkehrsentwicklungsplan_2010_2020_text.pdf

“Recommendations for Cycling Infrastructure” provide the legal and technical basis for construction of cycling infrastructure. An overview on relevant design guidelines and practices can be found here:

http://www.nationaler-radverkehrsplan.de/en/transferstelle/#infrastructure