Modern cars are much more efficient than their predecessors particularly in braking with better and wider tyres and anti-lock brake systems. Some high end cars now have automatic pre-braking type systems which sense the approach of an obstruction and begin to apply the brakes before the driver can react. Their fuel economy is also far greater than the earlier vehicles usually double if not triple in some cases.
As for the speed limits, I have been down roads where the limits change every 10-20 yds from 20mph to 50mph and ones in between. There are times when it is almost impossible to keep track of the current limit with so much other “street furniture” to watch out for. Sometimes there may be as many as 6 or 7 signs to read at once and some will get missed, the brain can only assimilate so much information at once and the driver has to drive the vehicle at the same time safely.
By standardising and simplifying the speed limits should make the roads safer by allowing the driver more time to concentrate on the road. Greater efforts should be made, concurrently, to inform and educate the pedestrians on their personal responsibilities on using and crossing roads. Where a particular problem becomes evident, measures to separate road users from pedestrians (e.g. a fence) should be considered, rather than just blaming the motorist and reducing the speed limit every time someone gets killed. It is unfair to always blame the motorist when the pedestrian is probably at fault in some way.