Walking in Waterloo Region

[tomh009]

This guide to guardrailing suggests that the use of guardrails should be considered a last resort.

Not quite as a last resort, but they suggest selective use and careful consideration rather than putting railings everywhere.  For example:

The safety benefit of preventing a sudden or unexpected influx of pedestrians entering the carriageway is not in doubt. Traditionally, at locations with high volumes of pedestrians, especially those frequented by children, such as school entrances/exits, playground areas, leisure centres, transport interchanges and exits from alleyways or stairways that lead directly to the road edge, it is unlikely that existing guardrailing should be removed. Thus, the assessment procedure described in this LTN is designed primarily for pedestrian crossing and road junction sites.

and

For roundabout sites, an average of 90 per cent of pedestrians were found to cross within the designated crossing area at sites with guardrailing, compared with 32 per cent at sites without guardrailing.

The study also mostly deals with UK urban environments, rather than the car-centric suburban arterial roads where we currently have roundabouts; the environments really aren't the same.