As you said above, the majority will be HGVs, buses or other commercial vehicles as cars are, for the most part, too low to hit them.
It is worth remembering as well that if you passed a driving test for a car prior to 1996, you will have a category C1 licence as well. Allowing you to drive a 7.5 tonne truck. And anyone with a car licence can drive a 3.5 tonne Luton Van. These vehicles, whilst not quite in the same league as a 44 tonne Artic height wise, are still tall enough to be scalped by the lower end of the low bridge scale.
The point I am trying to make here, is that it may not necessarily be the case that all bridge strikes are cause by professional drivers.
Anyone with a car licence can go down to a hire place and pick up a fairly tall vehicle and drive away, having never driven such a vehicle before.
It would be interesting to see the a breakdown of how many strikes were caused by inexperienced drivers in hire vehicles.
it would be interesting to know how many bridge strikes are caused by British drivers, and by those from other countries, such as from the EU who may not be familiar with imperial measurments
Maybe something similar to the old style lading guages at railway freight yards? One still stands folornly at Totton, the yard having been cleared and developed. something set to the same height as the bridge to sound a warning in advance
The bridge at Ampress just outside Lymington is one that sees strikes on a regular basis
I would be interested to know that as well, as I would tend to agree that a foreign driver will probably have never heard of Feet and Inches, before coming to the UK, as we are I believe (but stand to be corrected), the last stronghold of the Imperial measurement in Europe.
As an aside it can be rather inconvenient to be behind a continental wagon, travelling at 30 or 40 kph, when the speed limit is 30 or 40 mph.
I think that maybe presenting a continental driver with a simple conversion chart, or something like that at Dover, or wherever they enter could help here.
There are some bridges (mostly ones that have had the s*** knocked out of them in the past), that have some form of prior warning before them.
There is the electronic warnings mentioned before, but as GJ alluded to, these aren't always entirely reliable.
I have seen some with bash bars set a few feet away from the bridge, and some with a string of bells suspended across the road (although this is more common in the case of low hanging electrical wires, they are sometimes used at bridges)
In the USA I have noted that some low bridges have a hinged sign a few hundred yards before proclaiming "IF YOU HIT THIS SIGN, YOU WILL HIT THAT BRIDGE".
The issue with loading gauges, a good idea though they may seem, is that in common with signage, they are vulnerable to being damaged, removed or set at the wrong height.
The simple fact is, these things happen, it's inconvenient I accept, however there will probably never be a solution to it as long as humans are able to make mistakes.