This morning I rode through the Dalmeny estate on my commute loop, so for reference:
It's 2.59 miles between the junction with the bizarre "bike gutter" (near Dalmeny village) to rejoin the slip road onto the A90 at Crammond (the road carrying traffic from Kirkliston).
Took me just under 10 minutes, including stopping for a tractor - and I wasn't racing. There were no potholes, just flawless road surface and the couple of estate cars I passed were very happy to see me.
In contrast, from a GPS trace when I used to commute to Fife, the A90's 24"-from-oncoming-70mph-HGVs option is 1.55 miles and took 7 minutes.
There is more climbing on the estate route because you drop almost to sea level, but clearly the time cost is small - just three minutes.
I strongly encourage people going out this way to have a crack at it, it's *way* better than the official path in every imaginable way.
Turn off just before the bridge at the top of the slip road (the streetcar doesn't go to the second road, but either of them will do as they both join up 10m in).
There are a couple of turn-offs to ignore, but follow your nose on the "main" road and you'll eventually get to a junction beside a stream where (bizarrely) there's an NCN sign pointing right. Ignore it and turn left, and you will arrive at Dalmeny house. Bear left to start climbing steadily back up to the junction near Dalmeny, job's a good one.