Following an investigation into the death of a cyclist, a New Zealand coroner has publicly called for high-visibility clothing to be compulsory for all cyclists. Wellington regional coroner Ian Smith reckons it’s a “no brainer”.

Coroners undertake expert investigations into the circumstances surrounding deaths. They provide an invaluable service to the community in ensuring information about risks to life is drawn to the attention of governments and the wider public.

Yet they sometimes — and seemingly increasingly — tend to make sweeping public policy recommendations based on the circumstances of one particular case. Moreover, they tend to give insufficient weight to, or ignore entirely, basic concerns of policymakers like costs versus benefits, practicality, equity implications and community acceptability.

On Friday, NZ blogger Eric Crampton listed 22 cases where coroners had made recommendations on matters of general public policy ranging from improved privacy controls to age restrictions on access to butane and other inhalants. Here are the recommendations that seem to relate to development:

I don’t doubt there’s a good chance many of the deaths investigated would’ve been avoided if these coronial recommendations had been implemented at the time.

But in too many cases there’s little sense the coroners think about the public policy implications. This tendency to make policy in a vacuum — to extrapolate to the wider world from one highly specific case — happens in Australia too, and of course the media love it.

Last week The Age ran an editorial — “Why don’t our children have seatbelts in buses?” — arguing seatbelts in school buses should be mandatory. The writer drew authority from a March 2011 recommendation by the state coroner, Heather Spooner. She investigated the deaths of three people in a bus accident in 2009 and “called for several changes to this state’s policies on seatbelts in buses”. Mandatory seatbelts in school buses would seem to be another “no-brainer”, surely?

Perhaps, but there’s more to it. We need to think about how effective they’d be and what they’d cost.

study in the 1990s by Austroads found 24 children aged five to 17 years were killed while travelling to and from school during the three years studied. However, only two of those children were killed while riding in a bus. The most dangerous part of bus travel for children is getting to and from the door to the bus, especially in the afternoon. That’s when they’re most likely to be hit by another vehicle, or by the bus.

Yet the main travel risk for children isn’t buses at all. A study by Professor David Hensher found it’s more dangerous for children to be driven, or walk or cycle, than travel by bus or train.

When exposure is accounted for (that is, kilometres of travel), taking the bus is 1.4 times safer in terms of the risk of death or serious injury than being driven; 4.4 times safer than walking; and 55 times safer than cycling. Travelling by train is safest of all.

Fitting buses with seatbelts is costly. In Western Australia, where seatbelts are being phased in over a 10-year period, it costs $26,000 to install seatbelts on a bus. However, if structural changes are required in older buses, such as strengthening mounting points, it can cost up to $71,000.