Driving from San Gim to Venice

First approx 10 km. from San Gimignano to Poggibonsi: two lane highway. At Poggibonsi (North) enter Freeway (RACCORDO FI-SI).
Then it's freeway all the way (4 to 6 lane). Not sure why you would park in Mestre. You should exit at Mestre and take the Via della Liberta' through the Ponte della Liberta' all the way to Venice. There are lots of parking structures across the bridge on Piazzale Roma and the Tronchetto island.

Thank you, Roberto. The reason for parking in Mestre is that I read that the causeway into Venice has delays due to construction. Didn't want to end up a major traffic jam.

But the time it will take you to park in Mestre, schlep your bags to the train station, wait for a train and then go into Venice will surely take longer than a traffic jam...

Thank you again. You certainly spelled it out for me. Was a little anxious about the tolls having already gotten a ticket on a previous trip.

Its probably 6 of one and half a dozen of the other. I've always parked over the road from the Mestre station in the high rise car park. Its cheaper (at least it was always €10 a day cheaper) and yes you do have to cross the street and catch one of the trains which come every 5 minutes or so. You then pop out at Ferrovia above the Grand Canal and you are golden. If you drive over the causeway you have the traffic, the speed cameras, getting into the Tronchetto building or P.Roma garages, and then use the peoplemover or dodge the buses.... so its pay your money and make your choice...

I made the same drive last April. Other than the short ride to Poggibonsi, the roads are controlled access virtually all the way (about 175 miles.) Traffic is pretty busy and roads a little crooked from Florence up to Bologna. Terrain is flat the rest of the way, and traffic moves briskly. My only warning is on the causeway going over to Venice. There are radar cameras looking for speeders. I later got a bill from Hertz for their paying a fine for me.
There is a vaporetto stop at the end of the parking garages which will take you right to St. Marks Square.

Thank you all for your input. I forgot to ask about tolls. Since I don't have a chip and pin card, I am assuming I can use cash for the tools. Will I need exact change?

Tolls instructions
The freeway from Poggibonsi to Florence (Raccordo SI-FI) is indeed free. No tolls required. When that freeway ends it will put you on a roundabout with a diagonal statue in the middle. Take the roundabout exit that puts you on the A1 freeway (see the green signs). That freeway entrance is called FIRENZE IMPRUNETA. The A1 freeway is not free, it's a tollway. As you enter there are toll booths. Get your ticket from the machine (it works similar to a parking garage where you pick up the ticket when you enter). Choose the right booth, because some are for Telepass users (people who have transponders and pay electronically). Keep that ticket with you for the entire trip. After getting your ticket follow the directions to Bologna (A1 North). When approaching Bologna keep an eye for the freeway that takes you to PADOVA (A13). Before Padova then you will look for the A4 freeway (the MILANO-VENEZIA). Follow directions to VENEZIA. When you exit the freeway in Venice Mestre, there will be another similar toll booth. Choose the cash payment booths, not the Telepass or ViaCard. Hand your freeway ticket to the toll booth guy exactly as you do when you exit a parking garage in America. The display will show the amount you owe. You don't need to give exact change, the guy will give you change back. I don't know if there is construction going on the Liberty Bridge at the moment. If you park in Mestre and take the train in, the last train coming back to Mestre leaves Venice SL at 12:36am, after that you'd need a taxi until early morning.

Parking in Mestre is a little cheaper than Piazzale Roma. Generally Euro 10/day on weekdays (Euro 15/day weekends). At piazzale Roma is about Euro 20/day. If parking at the airport is only Euro 5/day, that would be cheaper than Mestre only if you stay more than 2 days.

Another option you may want to consider, drive a little longer to the airport and park there. 5 euro a day parking (at least as of last Feb and much cheaper than a garage in Piazzale Roma or in Mestre)and take the 20 min. bus ride into Piazale Roma which was, I think, 10 euro.

Thank you, Ron. Hadn't thought of that. Will research that option, too. Sounds easier than parking in Mestre.

When we were in Venice in 2011, we stayed in Mestre and drove to the parking ramp at Piazzale Roma. At the parking ramp, the attendent wanted us to leave the keys in the car so he could move the car into a good parking place. After walking away for a few minutes, my husband decided that wasn't such a good idea so he went back to the car, moved the car to a different place, took the keys and locked the door. Perhaps everything was legitimate but... We felt better about having the keys in our possession. Also, since that was two years ago, maybe the "policies" have changed.

Thanks for the head's up about leaving the keys. Obviously, would not want to take that chance. Am leaning towards Mestre or the airport.

If I was back in Venice, I wouldn't have a car and would just pay the money to stay in a hotel in the city. If I had a car, I would still park at the Piazzale Roma but take the keys. We needed to drive to the Piazale Roma so we could we could see the cruise ship arrival area where we were picking up friends the next day. It really depends how much time you are willing to take to commute to get to Venice. I wouldn't be concerned about parking at the Piazzale Roma.