A national speed limit is imposed on the <a href="https://en.wikipedia.org/wiki/Autobahn" id="mw9w" rel="mw:WikiLink" title="Autobahn">Autobahn</a> in Germany because of the <a href="https://en.wikipedia.org/wiki/1973_oil_crisis" id="mw-A" rel="mw:WikiLink" title="1973 oil crisis">1973 oil crisis</a>. The speed limit lasts only four months.