Note that the number of parking spots near the institute is very limited.
... from Frankfurt airport:
From Frankfurt airport take the AirLiner bus (AIR) (Schedule) to "Darmstadt Kongresszentrum" (convention center). From there it is a 5-10 minute walk to the institute, see map below. The bus leaves every 30-60 min, takes approximately 40 min and costs 8,45€.
... from Darmstadt Hauptbahnhof (central station):
At Darmstadt Hauptbahnhof, take the tram number 5 to "Kranichstein", or the bus number K to "TU-Lichtwiese/Mensa". Exit the tram/bus at the fourth stop: "Willy-Brandt-Platz". From there you can reach us within five minutes by foot: Follow the Bismarckstrasse in East direction and walk straight through the large park (Herrngarten). After leaving the park you are in the Hochschulstrasse and you can see both to your left and to your right old red-brick university buildings. Follow this street for about 100m until you reach a small square (Kantplatz). Turn to the left and follow the Schlossgartenstrasse for another 100m. The theory center is the second building on the left-hand side (building number S2|11).