Salzburg- Grossglockner round trip.

The driving time (without stops) would be at least 5:30 hours, assuming you go from Salzburg (via Kaprun) to the Grossglockner alpine road, heading south over the pass, go to Spittal/Drau, and from there straight back to Salzburg via the A10 highway.

That is the route:
https://www.google.com/maps/dir/Salzburg,+%C3%96sterreich/Heiligenblut,+%C3%96sterreich/Spittal+an+der+Drau,+%C3%96sterreich/Salzburg,+%C3%96sterreich/@47.3160181,13.2156172,9z/data=!4m14!4m13!1m2!1m1!1s0x47769adda908d4b1:0xc1e183a1412af73d!1m2!1m1!1s0x47776acfa2ce7fd7:0x8d3186646f07359e!1m2!1m1!1s0x4770a2e1fd11a72d:0x8de1512ccc09a8ee!1m2!1m1!1s0x47769adda908d4b1:0xc1e183a1412af73d!3e0

There is a big multi-story garage at the top of the cable car (the cable car is unusual there in that it takes people from a high point down to the old (1950s) glacier base, which is now several hundred meters removed from the glacier itself due to glacier retreat/rising temperatures. There are restaurants and other facilities up there. Make sure to stop at the different vantage points along the route.

You don't need to backtrack, there is a faster route with a tunnel taking you through.

Hello, Small world. I was plotting a similar road trip yesterday. In several weeks we plan to approach the GrossglocknerStrasse from the NW, coming down from Chiemsee -- so the routing will be a bit different. Like you, we will then head back north, by Salzburg, to Mondsee. Disclaimer: this is all based on websites and maps; I expect more reliable advice will follow from the Austria Forum regulars.

I would suggest using GoogleMap or ViaMichelin to investigate something like the following:
1. Route from Salzburg to Zell Am See, then the short drive down to the northern end of the GS at Ferleiten. Rts 21 to 78 to 311 looks promising. Others with real experience will hopefully give you better suggestions.
2. Travel the GS to southern end at Heiligenblut.
3. (The following is our scheme) from there: Rts 107 and 106 east to Seeboden; get on A10 for a relatively straight shot back to Salzburg.

You should have plenty of time with a moderately early start. Looks like the drive to the start will be about 2 hours. Others on the Forum have suggested 2 hours+ for the GS drive, but dining and admiring the views probably make this highly variable. The return to Salzburg will be 2.5 hrs or so, depending on route. (One is a partial backtrack on the GS.) More info on the Grossglocknerstrasser website: https://www.grossglockner.at/gg/en/index

A fantastic day out - if the weather is better than today.

First, you do know the road has it's very own multilingual website? https://www.grossglockner.at/gg/en/index

Departure time: Give the city workers time to get in, set off 08:30-09:00. Depends where you are staying, Salzburg city traffic can get itself into horrendous gridlock at times. For most districts I'd get the B150 south to the A10 autobahn south of the zoo then on that until the B311 near Bischofshofen, west to Bruck and then the fun really starts. Don't forget Austrian autobahns are toll roads, the car needs a sticker, rentals should have one.

The Grossglockner road also has a hefty toll, this is paid before the serious climbing begins, you ought to be at the start within 100 minutes of leaving Salzburg. The main site on the road is Franz-Josefs-Höhe which is actually at the end of a side road. It has a large underground parking lot (free) and other facilities.

There is a choice of cable cars http://www.gross-glockner.at/en/summer/tickets-passes/grossglockner-panoramabahn parking areas tend to be rough flat sites, I'm not sure about costs, they may be free in summer (they are really for the ski season).

Both the websites have webcams, this is important because the weather can be very different to what it is in the city, low cloud may cover Salzburg but the road and summit could be above it in sunshine. Check them out at breakfast time.

Alternative return route is simple, if not faster. Carry on a little further south to Lienz (which is definaetly not the same place as Linz). From here head north west on the B108 Felbertauern road http://www.felbertauernstrasse.at/en/ (with another webcam). If you plan on using this route you can save money by buying a Rundfahrt ticket at the Grossglockner toll booth, this gives you one trip on each road at a slight discount to the total of the 2 prices. At Mittersill head east on B168. This takes you almost back to Bruck. You can return to Salzburg on the A10 or turn north on B311 via Zell and Saalfelden to Lofer then B178 which should be signposted for Salzburg. But before you get there you pass through a corner of Germany (normally no border controls and most of the cars on the road will have Austrian plates). This road is the B21 in Germany and re-enters Austria near Salzburg airport. The trick here is not to arrive too early, traffic is once again chaos in the evening rush hour. Allow 3 hours Lienz-Lofer-Salzburg.

Wow... Thanks for all the great responses... Sounds like I have many options... My hotel is Der Salzburger Hof-- Address is Kaiserschützenstraße 1, 5020 Salzburg which is east of the River near the train station. So I'm assuming that that means getting in/out will involve rush hour traffic...

it is well inside the city but a fairly straightforward route out south with only a couple of places with delays. Coming back via Lofer it might be easier to get on the A1 autobahn near the airport and go around the northern edge of the city until you've crossed the river.