Given this disparity, and the fact people are dying, perhaps it really is time for a debate on the issue.

I'd agree with that. As a first step it would seem sensible to treat arable farm land in the same way as a road.

   - Andy.

indeed - but unless folk call in the dodgy sections, any rule change will only affect the new stuff - a very small fraction of the total.  I must say that the idea that 8 inches holds off the difference between 66kV to 33kV and 11kV down  to LV seems a bit silly - on that basis it could all be 'nominal 6 metres' and easier to remember and not make much difference at all.
Equally if the combine  harvester is really is 5m tall - are they really? then unless the uplift is dramatic - pylon sort of dramatic, rather than taller trees,  it  is not going to help a lot. Also I imagine a lot of farmers are pretty hazy on the actual line voltages of things crossing their land.

Mike

any rule change will only affect the new stuff

True, but that's true of most changes - from safety belts to RCDs - but nevertheless tempus does fugit.. While new lines might be relatively rare, wooden poles do seem to be replaced on a fairly regular basis (few decades)- so there could be a significant improvement in a sensible length of time.

I wonder if growing the trees higher to make the poles might be more of an issue (as well as taking longer, at some point they won't fit into the processing plants or transport vehicles).

   - Andy.

any rule change will only affect the new stuff

True, but that's true of most changes - from safety belts to RCDs - but nevertheless tempus does fugit.. While new lines might be relatively rare, wooden poles do seem to be replaced on a fairly regular basis (few decades)- so there could be a significant improvement in a sensible length of time.

I wonder if growing the trees higher to make the poles might be more of an issue (as well as taking longer, at some point they won't fit into the processing plants or transport vehicles).

   - Andy.

well round here on the LV network, some of the droopier poles now sport an extension that looks to be aluminium or maybe a bright galvanized washing line pole type thing , that bolts onto the holes where the ceramic insulators used to go, and adds a metre or so, and then carries the LV  aerial bundle cables 'ABC' on top of that.
We have a lot of house feeds that cross the road to go to the eaves on bungalows and these pole extensions seem to be to raise the tall end  triangle a bit, and it gets done when the 4 wire singles get replaced for ABC - which is slowly working out from the town centre up the hill. As far as I can see the houses remain 2 wire TT, but the street cable changes, so in principle could be PME in future. (I'm sure it was supposed to be PME ready years ago, but like fused neutrals, let's just not ask..  )

I suppose a similar top hat idea could be engineered to replace the 11kV cross-bars with slightly taller metalwork without pulling out the pole or growing taller trees... We also have some 11kV where the wires are one above the other rather than side by side, I presume it has better wind-sway clearnace as it is only on exposed bits of the new forest.

Mike.