From the article above:
Hilden in Germany brought in a 30 km/h (19 mph) in 1991. They found that:
‘the roads were safer, more people cycled and walked and, as the proportion of motor vehicles reduced, air quality improved.’
Spain has had the same limit on single-lane streets in all cities since 2021. The head of Spain’s National Road Safety Observatory said:
‘There are no big delays, there is no congestion. There is no increase of pollution. Everything becomes normal, and everything gets better.’
‘Last year the number of pedestrians killed in Spanish cities was 14 per cent less than in pre-pandemic levels, with even fewer deaths among the elderly’, says The Times.
The risk of a pedestrian being killed when hit by a car is five times lower at 20 mph than at 30 mph.