30km/h makes sense on urban roads. If you need to go 15-30km to get to your grocery store you probably live a lifestyle where you plan that trip, use a freezer and so on. Unless that trip happens to be a motorway/freeway.

Fast motorways are incredibly safe because no pedestrians and energy absorbing crash barriers and traffic control/monitoring. There are exceptions e.g. where there is fog for example.

Fast roads in cities should ideally be designed so it is really hard for pedestrians to get on them except at the intersections.