Hm. Possibly an error with handling oneway=no on the parent way. I’m away from the code at the moment but will check once I’m back. 

I'm interested in this as I'm trying to improve my knowledge of openstreetmap. Irrespective of what your checks show Richard, on the ground, there is a chained gate that is not meant for cyclists and a non-gated bypass that is. As far as I can tell, the Barrier=gate tag is meant for gates the cyclist has to open to achieve access. I've checked some similar features local to me that are the same in principle on the ground, and they are not mapped as gates. If I'd be better off on an OSM forum, please point me in the right direction. I've tried to find standards on mapping this type of complex entity but failed. Thanks, Graham

Usually in such circumstances, the trick is to draw two parallel ways. One would have a gate on it with access=private (to represent that it’s chained shut), the other no gate. The ways would connect either side of the gate. But to be honest, if you can always get round the gate then I wouldn’t worry too much about mapping it!

Thanks, that's logical and what I'd have expected best practice to be.

On the original issue: I haven’t figured this one out yet. It’s not the gate, it’s the junction of Castle Road, Heol y Fforest and the access road. For some reason it won’t route north across this junction. It might be that something’s skewy with the turn analysis; this is harder to debug than the road weighting but I’m looking into it.