December 9, 2012 10:00am by David Farrar

HoS on drink driving limits

New figures released by the Ministry of Transport are effectively that New Zealand research and confirm beyond doubt that the Government must act now to lower the blood-alcohol limit.

The data, released under the Official Information Act, reveals at least 20 people have been killed over the past four years in road accidents in which the driver had an alcohol reading of between 50mg and 80mg.

I don’t have the data they have under the OIA. But I suspect that the stat they quote includes drivers who are aged under 20 who already have a legal limit of 30 (now 0). The relevant stat is how many drivers who can legally drive at 50 to 80 mg blood alcohol have fatal crashes. Hence if you change the law (and assume that those drivers will obey the new law) how many fewer fatal crashes might there be.

Now again I don’t have the OIA data (but happy to be sent it), but we do have 2008 to 2010 data on the Transport website. The data for the number of drivers killed who were over 20 and had a blood alcohol level of 50 to 80 is three per year over those four years.

Now there is definitely a case to say three fewer fatal crashes per year is worthwhile – it is. But what we don’t know (and what the data is being collected for) is how many people drive at 50 to 80 blood alcohol and would be affected by a lower limit. Without solid data, how do we know whether the limit should be 50, 80, 30, 65? It is easy for media to portray an issue as simple and not complex – but I think it is the duty of Government to understand the impact of a proposed law change -how many drivers will be impacted by it, and what is the accident rate for driving at that level. If you don’t have data on the prevalence of driving at that BAC, you can not calculate the accident rate.