Thank you for your post. I have to correct myself regarding the timing of the introduction of the national speed limit and the fall in road deaths. I now find the statistics for road death numbers were only looking at a sub-set of the total. I have found a clear graph on Wikipedia (usual conditions apply!) covering all deaths which can be found at <
https://en.wikipedia.org/wiki/Reported_Road_Casualties_Great_Britain>. The first national figures were reported in 1926 when 4,866 people were killed at a time when there was a total of some 1.5 million vehicles of all types on the roads. The peak was reached in 1941 with 9,169 killed although essentially only official and military vehicles were on the road. This must have been connected with risks people were prepared to take in wartime, the blackout with no street lighting and vehicles driving on, effectively, side lights and one masked headlight. The rate fell to 5,000 in 1950, by which time the number of registered vehicles reached 3,970,000. With not only the number of vehicles increasing but also their power the post-war peak of 7,985 was reached in 1965.
The 70mph limit became nationwide in 1967 so I retract my suggestion that speed had nothing to do with the ensuing reduction. I would however add that the reduction in speed was only one of the contributory factors - seat belts, laminated windscreens, elimination of the steering column solidly connected to the front wheels and pointing right at the driver's heart, crumple zones, side impact protection and, very importantly, the change from tubed cross-ply to tubeless radial tyres all played important roles and were progressively introduced from the late 60s/early 70s.
Air traffic safety has been benefited by more reliable and more powerful engines and more robust airframes. But the biggest change is improved flight control and navigation systems so that planes don't fly into hills so often. Planes now have the ability to know exactly where they are at all times - not only jet airliners but the smallest Cessna can now have the same facilities as big jets. Aircraft safety has not been improved by reducing speeds - although improved aerodynamics in modern planes has shaved a few knots off landing and take-off speeds (depending on weight) compared to roughly equivalent older machines.
Which brings us back to railways...! The number of train accidents due to excessive speeds on open track has been very small. There have been some, Morpeth, Paddington(1983) for example. But the recent limitations in speeds are mostly concerned with avoiding SPADs by restricting the speeds when approaching signals. These restrictions are more severe than are needed by a skilled driver and are determined by the technology of the time when TPWS and the two trial forms of ATP were introduced on the Chiltern and GW routes and current standard operating instructions. Little or no effort seems to be made in aligning the restrictions caused by these factors to the speed which could be achieved considering that braking control is more consistent these days. The unique selling point of the railway is speed - it's certainly not cost or comfort these days - so why are these limitations simply accepted?
