I drive on average 25K miles (40K km) per year, mostly intercity and done so for the last 12 years, 10 of them in UK and the last two in the West of Germany.

I used to think autobahn and specifically the lack of speed limits was a great design and that British top speed of 70mph (110km/h) was somewhat dated. Now, having driven about 50K miles (80K km) in Germany, mostly on autobahns, I prefer the design of British motorways.

First the signage. On German autobahns it is extremely easy to miss a speed limit sign. The signs are the same size as regular "slow" road signs and often displayed only on the left side of the autobahn, they are very difficult to spot from afar, can be blocked from view by other vehicles and easy to miss when momentarily concentrating on the situation developing on the road. The speed signs are almost never repeated. On the contrary in UK the signage is done with much better understanding of how humans operate: motorway signs are bigger than their regular road counterparts, easy to spot from afar, installed in clear view on the both sides of the motorway, often repeated a few hundred meters later.

Then the speed limits themselves. They are far from thought through. For example a no speed limit stretch can suddenly, without any apparent reason, have a 80km/h (50mph) limit sign, then 300 or 400 meters later (quarter mile) another sign removing any speed limit. This leads to quite a lot of sudden breaking and many drivers ignore the limit slowing down only to 120km/h or so. Another example would be a "end of all limits" sign after a long 130km/h stretch in the beginning of an steep ascending stretch, followed with the 100km/h limit a mile or later on the top of the hill. Literally encouraging unaware drivers to pointlessly burn fuel accelerating up the hill.

The top speeds can rarely be attained in Germany unless at night. Traffic and roadworks leave a few short stretches where one can go faster than 130km/h. But this leads to constant acceleration and breaking and many many emergency breaking. Chain accidents are very common.

Cruise control is pointless due to constant speed adjustments. Adaptive cruise control doesn't work well either as it requires a certain distance to the car in front to operate safely, but overtaking from the right is very common and most German drivers hence leave a very short distance, essentially tailgating.

I find that the UK system, there traffic progresses steadily at a constant pace of around 70..80mph to be safer and less tiring.

German roadworks, including non-essential, are scheduled with little or no regard to the expected amount of traffic (e.g. public holidays, peak traffic hours etc). In UK system this type of planning gets a lot of consideration.

Diversions on Ferman autobahns are cryptic, signage is very scarce and they are practically impossible to follow without supplemental info (i.e. satnav). Diversions in UK are clearly marked and much easier to follow.

UK rest areas (services) are head and shoulders above their German counterparts and include free toilets.

All in all, I believe, German autobahn network is great, but UK motorway network had much more consideration for how humans work put into its design.