From westerly direction to Stuttgart via AB A8/A81 and B14:
Trains S1, S2, S3 use underground parking "Unterer Grund"
Closed between 01:00 and 04:30 o'clock no exit possible!
Use 2-Zone ticket travel to center (Stadtmitte) in 9 minutes continue on to stop 'Bad Cannstatt'
From south to Stuttgart via B27:
Parking lot Degerloch,
24 h exit possible
Directly adjecent to stop 'Degerloch Albstraße' - next to Bundesstraße B27 - the SSB has constructed a Park & Ride facility. Special offer: The parking fee ticket is also a day ticket train rides into the city center.
Link - more Information at SSB