Quite by coincidence (no really) we are on holiday in SW France as the Tour is going through the Pyrenees. I’m keen to go and watch a stage and have the beginnings of a plan in my head.

Stage 17, Weds 23rd July, St Gaudens to Saint Lary Soulan Pla d’Adet.
Drive to Loudenvielle (the route goes through here).
Leave the car and family there. I know the place as it was the finish of the 2007 etape du tour, it has a pretty lake with water sports etc to keep all amused.
Ride, almost certainly just me, up Col de Val Louron-Azet (penultimate col of the day), find a spot and wait for the pros to come past.
Ride down, pick up family, drive home.

Does this sound like a reasonable plan?
Will I be able to leave the car in or near Loudenvielle?
How early do I need to get to Loudenvielle, in order to park, have time to ride up and find a spot?
How long after the back marker comes through can I ride down again?
I assume the traffic will be pretty horrendous, but how horrendous?

Any other advice, like take lots of sunscreen, water, changes of clothes…

The road will likely be shut from early in the morning. Parking will most probably be an absolute nightmare.
You will be able to walk up after the road is closed, but the Gendamerie don’t like people riding up. So take some trainers in a back-pack along with some food and water.

Stand by a bunch of kids if you want to collect more stuff from the carnival 😉

You can leave as soon as the broom wagon goes through.

It is a mixed bag with gendamerie some will allow you to ride up some will insist you walk (but once around the corner just get back on and ride, possibly depending on how close the tour is to that spot).

They allowed us to ride up the Peyresourde a couple of years ago. No Problem.

It maybe a easier to park if you drop the wife and kids in town. Then park further out of town and ride back in and up the hill. You can meet them afterwards and go back to the car and then drive to pick them up again.

We drove in to the Col de Manse stage last year, it wasn’t stupid early but we got within a couple of minutes walk of the hairpin on the descent to Gap (for those that know it) then walked up the road until we found a nice spot.

I guess it depends on location, but have a plan B in place in case you cannot get as far in as you’d like by car?

Roads were open straight after the wagon, the anticipation of the race arriving (and the caravan) makes for a great atmosphere, then it’s all over pretty quick.

Don’t know the geography as such but your plan sounds similar to what we did last year in the Col de Croix Fry, left the car in Thones and then cycled up to Manigod had some (11am)cake then lunch and then further up to the summit, Gendarmerie were not really interested. The descent off the mountain in the pissing rain past all the stationary traffic was good though!

There were plenty of people riding, we did the AdH stage by bike and not a bit of hassle.

The expected arrival times at various locations along the route will be published on the Tour site, if you’re riding up then aim to get there an hour or so before.