Germany's Federal Environment Agency has urged the government to introduce speed restrictions on the country's famously limit-free highways.
The idea is included in a package of measures put forward to reduce carbon emissions from private vehicles on German roads.
Germany's Süddeutsche Zeitung on Thursday cited an internal document from the agency that urges drastic action to meet the country's climate targets.
Among the proposals is the introduction of a maximum speed limit of 120 kilometers per hour (75 miles per hour) for vehicles on all German highways.
Such restrictions would likely spark huge controversy. At present, there are no official speed limits on certain stretches of road and drivers regularly hurtle along at speeds of more than 200 kph.
'Ambitious but feasible'
The unpublished policy paper also envisages a steep rise in tax on diesel — currently taxed at a lower rate than ordinary gasoline — of €0.70 ($0.78) per liter by the year 2030. Such a rise would represent an increase of almost 60%. Petrol would rise by €0.47.
Proposals also include a sharp increase in road tolls for heavy goods trucks, and an abolition of the country's "commuting allowance," which allows people traveling longer distances to work by car to claim tax rebates.
Germany could face EU penalties if it fails to reduce greenhouse gas and poisonous nitrogen oxides emissions. Observers consider the transport sector as a key to meeting emissions reduction targets.
The country aims — by the year 2030 — to reduce its carbon emissions to 55% of the level they were in 1990.
According to the document seen by the newspaper, those goals were "ambitious but feasible."
No desire for limits
In November, the Netherlands cut the daytime speed limit for traffic in the daytime to 100 kph, in an effort to tackle an emissions pollution crisis and improve air quality.
The German government has already said it has no plans to introduce a speed limit on Germany's autobahn network. That came after a government-appointed commission on the future of mobility suggested an upper speed limit of 130 kph.
And in October, German lawmakers overwhelmingly voted against a Greens proposal to impose speed limits.