he was a major reason why they were able to be built at all

Dead wrong. Hitler campaigned against the Autobahn before coming to power. Once he did, he refused to divert skilled workers from military construction. The roads were built with shoddy steel unsuitable for military use, by conscripted students, political prisoners, and other unskilled labor.

Because the Autobahn was a rush job by the hapless and the hopeless, very little of it was actually completed. When the Autobahn was grandly inaugurated, only 200 kilometers was complete. 30 percent of the system was still unpaved in 1939, much of the rest was constantly under repair, and the majority of the Autobahn was one-lane traffic because Hitler revised its width to support military vehicles and they had to rip the whole damn thing up and start over.

Surprise, surprise: beneath the smug surface of Nazi propaganda, inept execution at gunpoint and any true success prevented by corruption and out-of-touch military dictates. Just like the war itself.

Who knows what state their economy would have been in if not for him

The German economy was recovering when Hitler took power; the Weimar government had already done the hard and thankless task of renegotiating reparations and was rapidly improving relations with the United States, in hopes of building a new free trade bloc that would circumvent the colonial powers. Hitler's insane racial vision, which foresaw a clash of civilizations with America, prevented that rational strategy from bearing fruit.

Instead, Hitler embarked on rearmament that alienated Germany's trade partners and bloated the government debt - to the point that the central bank had to issue secret IOUs. The deficit was running at 50 percent. It was completely unpayable unless the Germans won the war.

The reason the war came in 1939 instead of 1940 or 1941? Hitler's mismanagement had brought the economy back to the edge of hyperinflation, even after looting the gold reserves of Austria and Czechoslovakia to prop up the tottering Reichsmark. The government was paying arms companies with vouchers for tax refunds. Had Hitler not gone to war, within six months the German economy would have collapsed.

If not? Germany was poised to become a successful middle-income exporter which would have emerged as the fulcrum of a European trade bloc, which in turn would have allied with the United States to press Britain and France to lower their tariffs. Which, I'm betting, is an option most Germans at the war's end would have loved to have in retrospect.