I have tried to go back over the video of the race to identify some real time gaps. Here is what I found:
1. At about 4.3 km to go, the camera cuts away from Alaphilippe and Fuglsang just before they reach a sign reading "Gasthuis" at the side of the road. Assuming that it would take them about 2 seconds to reach the sign, the gap at that point was 1:07 back to Clarke/Mollema and 1:16 back to the VDP group.
2. At about 4.1 km to go, Alaphilippe and Fuglsang pass a man standing by the side of the road. Kwia and Trentin pass the same man about 45 seconds later.
3. At about 3.2 km, Ala and Fuglsang turn a corner. Kwia and Trentin pass that corner about 39 seconds later. Clarke and Mollema turn the corner about 57 seconds after the leaders. (Schachmann was somewhere in between these groups.) We don't see the VDP group turn the corner, but about 10 seconds later the coverage cuts to a helicopter view that reveals the VDP group is catching Clarke and Mollema. I would therefore estimate that VDP was about 1:00 behind Alaphilippe and Fuglsang with 3 km to go.
4. At about 2 km to go, Ala and Fuglsang pass a man at the side of the road wearing a black t-shirt and gray shorts. Kwia passes the same man 28 seconds later. At this point, Schachmann has almost caught Kwia and Trentin.
5. At about 1.6 km to go, Ala and Fuglsang pass a man on the side of the road wearing a QuickStep jersey. It is hard to tell exactly when Kwia passes him, because you only see it in the distance, but I estimate the gap to be 17 seconds. VDP passes that man about 26 seconds after Ala and Fuglsang.
6. At the flamme rouge, I time the gap between Ala/Fuglsang and Kwia to be about 4 or 5 seconds.
7. At about 900m, there is a left turn. Kwia takes the turn less than 4 seconds later. VDP takes that turn about 7 or 8 seconds after Ala and Fuglsang.
To summarize--just considering Ala/Fuglsang and the VDP group:
- the gap was about 1:16 with 4.3 km to go.
- At 3 km, the gap was about 1:00, meaning they cut 16 seconds off the gap in 1.3 km.
- At 1.6 km, the gap was down to 26 seconds, meaning they gained 34 seconds in 1.4 km.
- By the turn at about 900m to go, the gap was down to about 8 seconds, meaning they gained 18 seconds in 500m.