Best route from Hertz Sansovino in Florence

Couple of questions that will help us give you better advice:
1) How are you arriving into Florence?
2) Are you renting the car because you want to go places other than Siena?

Kent, I will have spent 3 days in Florence before I rent this car for a week in Tuscany. I used Siena as a general direction for my question. It is not our only destination. Hope this answered your questions.

gw,
Click on this link:
https://community.ricksteves.com/travel-forum/italy/is-piazza-venezia-in-roma-now-a-no-go-zone
And look for the post from Roberto, the 2nd answer on that topic.
If you click on Roberto's name, it's the link in blue, you will have the option of sending Roberto a Private Message, which you should do and include your question.
Roberto used to live in Florence and still visits there frequently. He has in prior posts given complicated driving directions similar to yours.
Apparently he has not seen your question yet. He probably will, or you can send him a Private Message now.

You do not risk entering ZTL, but whatever route you choose you will find several speed radars so be sure not to drive faster than 50 km/h in all urban areas.

IMHO the easier route is via del Sansovino - turn left to via Francavilla (this is obligatory) - via del Pollaiolo - via Foggini - big roundabout - viale Etruria (here there is a speed radar issuing a good percentage of fines issued in Florence) - enter A1 direction Roma - get out of A1 at the next exit and enter directly into the Siena highway. Yes, you have to pay a little toll, but it is not rocket science. You take a ticket (biglietto) as you enter, you pay at a manned booth as you exit. Toll lanes marked only "Telepass" need an electronic device and a subscription so avoid them. (But if the lane is marked both biglietto and telepass you can use it.)

A similar route is the easier one for getting back. Enter A1 at Impruneta (end of Siena highway), exit at Scandicci and follow direction for the centre of Florence. You will find on viale Etruria and you drive always straight to via del Sansovino. Also in this direction there is a speed radar just as you enter the Florence urban area; it is quite easy to pass it at speed and get a fine. It is well marked but it makes many victims.

Also your second choice is good but no so easy. Here the speed traps are in the stretch along the city wall, climbing the hill on via Senese, and a three of them between Florence and the highway. At Galluzzo follow direction as there is a detour along the village.

If going back through this route, there is a big trap: via Senese, in the direction from the highway to the center, is reserved to bus and you should drive through via del Gelsomino. If you enter via Senese you enter a bus line and you get automatically a fine. Again, everything is marked but it is easy to go straight instead of keeping right to via del Gelsomino.

Well, you can also drive through via della Bagnese (but there should be some works now along the route). Be sure not to get lost....

Do as asps2 says. Follow the green signs toward "Autostrade" (freeways). Follow directions to Roma, exit at the next exit (Firenze IMPRUNETA).

The toll system in the Italian Autostrade works exactly like a paid parking lot at the airport. When you enter (on the ramp) you pick up the ticket at the dispensing machine (just like when you enter a parking lot). Keep the ticket with you. When you exit, at the exit ramp, there are toll booths. Choose one with the white sign with the cash logo and a black hand holding the cash. That means it accepts cash and the black hand indicates there is an attendant. Give the attendant the ticket. He'll insert the ticket in a computer and the display will show how much you owe. Give the money to the guy, get your change from him (if any) and you are ready to go. Follow directions to Siena at the big roundabout after you pay toll.

When you go back, do the same. This time follow directions to Bologna and exit at the next exit (Firenze SCANDICCI) after you pay go toward the city center. Hertz will be on your right after a short while.

Thank you very much, asps2 and Roberto, for the information and direction. I'll take the A1.