Did Hitler plan and built the Autobahn? Not entirely, the first section of what would later become the autobahn was constructed and built before Hitler came to power. Construction on the Köln-Bonn Autobahn a 20 km (12 mi) section of autobahn running between Cologne and Bonn. The autobahn project was a way to create jobs during hard economic times.
After seeing a Tatra 570 at an auto exhibit Adolf Hitler said the V570 "this is the car for my roads". It is believed that Porsche used Tatra's designs because Hitler liked it so much.
The Tatra V570 was a prototype early 1930s car developed by a team led by Hans Ledwinka and Paul Jaray. The aim of the construction team was to develop a cheap "people's car" with an aerodynamic body. However the company's management decided that the revolutionary ideas introduced in the prototype should be introduced in large luxurious cars, and therefore the team abandoned the project of small cars. Both the streamlined design and the technical specifications, especially the air-cooled flat-four engine mounted in the back, give the T97 a striking resemblance to the KdF-Wagen of Volkswagen, which later became the Beetle.
So, in conclusion Hilter designed neither the Beetle nor the Autobaun.