Venice is on the east-west A4 autostrada, which connects with Padua, Verona, Brescia, Milan, and Turin. If you bring a car to Venice, you will have to pay for a garage or parking space.
A warning about parking: don't be waylaid by illegal touts, often wearing fake uniforms, who may try to flag you down and offer to arrange parking and hotels; drive on to one of the parking garages. Parking at Autorimessa Comunale (041/2727211. www.asmvenezia.it) costs EUR 21 for 24 hours. The private Garage San Marco (041/5232213. www.garagesanmarco.it) costs EUR 20 for up to 12 hours and EUR 26 for 12-24 hours. You can reserve a space in advance at either of these garages; you'll come upon both immediately after crossing the bridge from the mainland. Another alternative is Tronchetto (041/5207555) parking (EUR 20 for 1-24 hours); watch for signs for it coming over the bridge—you'll have to turn right before you get to Piazzale Roma. Many hotels have negotiated guest discounts with San Marco or Tronchetto garages; get a voucher when you check in at your hotel and present it when you pay the garage.