i came across this thread when I was researching what to do, yesterday. I agree with the assessment that the last 2.5 km to Sarrance and large sections from Sarrance to Borce were extremely nerve racking if you have a fear of heights. So, here’s what I ended up doing.
I walked from Urdos to Confranc Estación this morning, leaving the gite at 7:05. According to the sign near the end of the town, where trails goes off N134, it should take just under 5 hours. I stayed on the highway. The first km out of Urdos, there is a limited shoulder. The next 4 to 4.5 Kim’s the asphalt shoulder varies from 3 to 5 yds. Most of it is 3 to 4 yds. There is a concrete gutter along the asphalt for most of the way and then also a weed/dirt shoulder. You can really walk in that even if mowed. There were 40 vehicles in the lane of hat I was walking along, half of which were trucks. And by trucks I mean semis. There are a lot of blind curves and anytime I heard a truck I stopped and moved as far from the asphalt as I could. I ended up doing this for all vehicles. Most vehicles moved over, if they could, and/or slowed down. It took 1 hr and 40 minutes to get to the turnoff before the Somport Tunnel. I use GAIAGPS to track my walks and it said that I had gone up 275 meters and walked just over 7 km. I think the distance is inflated and was probably more like 5 to 5.5 km. For 3 of those km the hey was 3 lanes with Spain bound having two lanes. This is good as less to worry about vehicles passing each other behind you. I was very careful and alert but thought this was very manageable.
The next 8 or so km were on the old N134. There is a limited shoulder but you can’t really walk on it. Too much of a slope. Very limited traffic. 15 cars heading toward me and 12 going towards Somport. However, there were 55 bicyclists going down the hill, towards me. I think they took this opportunity of limited cars to fly down. Most were going faster than the cars. Many did not look pleased to see a walker on the road. It took me 2 hrs and 20 minutes to get to the Spanish border at Col du Somport, which included a 15 min break.
40 minutes from the top it got very windy.
On the Spanish side I stayed on the trail. In some places it is really steep. And there are a few short sections that will be challenging for anyone afraid of heights. But they are very short, over in terms of alcouple if minutes per section. Also, if you pull back and look at the overall view it will look scarier than if you focus on where your heading in the next 2/3 steps.
A little long winded but hope this helps anyone planning this route in the future.