Apax, together with its local partners the German insurance group Allianz and the airline Lufthansa, was selected as preferred bidder after Guy Hands, the financier who runs Nomura's City-based buyout team, dropped his original Dm2.2bn (pounds 800m) bid by nearly 20 per cent in the wake of the stock market crash.
The deal, which was held up by the recent German parliamentary elections, is expected to be signed next week. The new "Red-Green" government is insisting that the buyers guarantee not to float or sell the business for at least three years.
The Germans want to avoid the kind of rows that have followed similar privatisation sales in the UK. The measures are designed to stop the buyers making a quick turn at the taxpayers' expense.
The Germans are believed to have been put out by the behaviour of Guy Hands, who heads Nomura's Principal Finance Group. Mr Hands said earlier this week that he sees big opportunities in Germany but believes that prices are going to have to come down.
Tank und Rast ("Fill-up and Rest") owns and runs 700 motorway outlets, including petrol stations, kiosks, restaurants, and motels in Germany. It accounts for about 90 per cent of the market, giving the group a virtual monopoly of motorway sales.