January 6, 2015

Foreign drivers, again

The Herald has a poll saying 61% of New Zealanders want to make large subsets of foreign drivers sit written and practical tests before they can drive here (33.9%: people from right-hand drive countries; 27.4% everyone but Australians). It’s hard to tell how much of this is just the push effect of being asked the questions and how much is real opinion.

The rationale is that foreign drivers are dangerous:

Overseas drivers were found at fault in 75 per cent of 538 injury crashes in which they were involved. But although failure to adjust to local conditions was blamed for seven fatal crashes, that was the suspected cause of just 26 per cent of the injury crashes.

This could do with some comparisons.  75% of 538 is 403, which is about 4.5% of all injury crashes that year.  We get about 2.7 million visitors per year, with a mean stay of 20 days (PDF), so on average the population is about 3.3% short-term visitors.

Or, we can look at the ‘factors involved’ for all the injury crashes. I get 15367  drivers of motorised vehicles involved in injury crashes, and 9192 of them have a contributing factor that is driver fault (causes 1xx to 4xx in the Crash Analysis System). This doesn’t include things like brake failures.  So, drivers on average are at fault in about 60% of the injury crashes they are involved in.

Based on this, it looks as though foreign drivers are somewhat more dangerous, but that restricting them is very unlikely to prevent more than, say, 1-2% of crashes. If you consider all the ways we might reduce injury crashes by 1-2%, and think about the side-effects of each one, I don’t think this is going to be near the top of the list.

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Comments

  • avatar
    Dale Smith

    shouldn’t we be comparing visitors that drive rather than visitors per se?

    3 years ago

    • avatar
      Thomas Lumley

      Ideally we’d compare visitors that drive to locals that drive, but the data aren’t available easily. In fact, ideally we’d look at km driven, but that really isn’t available easily.

      I’d be surprised if just using population wasn’t within a factor of two or three, and it would need to be off my a lot more to change the conclusions.

      3 years ago

      • avatar
        Dale Smith

        As you point out the numbers aren’t readily available, yet they are collected re ownership and yearly registration forms (along with the fees).

        You would think that collecting info to help with accident prevention would be one of the reasons this info. was collected.

        One of the reasons I am interested in this is that I travel by car a lot and have seen numerous instances with tourist drivers where their actions could have and have had disastrous consequences.

        These tourist actions are far more numerous than any behaviour I have seen by non tourists. Yes my assessment of who is a tourist and who is not is subjective but based on some rational, more it would seem that what the present data collection allows to say otherwise.

        and it is not always about numbers but individuals. Last week my wife and I were one of the first on the scene of a head on collision. We attended a badly injured young women for over two hours before she was taken to hospital. She later died.

        If you asked the driver of the offending car if he could have (maybe) lessened his risk by taking a test at point of hire, I think I know what the answer would be.

        I agree that on the big picture list that it is not top priority but these foreign drivers are easy to access at point of hire origin and they could be charged for the test, as they are for the cost of hire, so no cost to NZ. It’s a small fee in the scheme of their total holiday budget so would not prevent tourists coming to NZ based on cost. It would prevent and stop tourists who had no knowledge, in spite of a foreign drivers licence, from driving.

        3 years ago

        • avatar
          Thomas Lumley

          Yes, collecting this information might be worthwhile.

          It’s not true that there is no cost to New Zealand though: changing the law to impose tests would require withdrawing from the UN Convention on Road Traffic, which is what gives New Zealanders the right to drive in many other countries. Also, it if becomes more difficult and expensive for tourists to visit New Zealand, they are likely to visit less.

          3 years ago

  • avatar
    Dale Smith

    I wouldn’t call them tests, more like education inspections, which you cannot fail them on but show them what they have to do to pass and would get the hire car companies to do it from their side so it is an internal procedure just like checking out their ability to pay etc.

    and as far as difficulty and expense and being bad for NZ tourism, Yes the dead Chinese tourist will never visit NZ again, the at fault and charged German driver will also be put of travelling here again, and the publicity that this will have received in both China and Germany can go in the same column as the odd robbery, rape and murder of tourists and NZ not being a safe place to travel.

    If the powers that be don’t want to do this, and that includes not gathering the right data, then you can always come up with excuses.

    3 years ago

    • avatar
      Thomas Lumley

      Yes, it’s easy to come up with excuses, isn’t it.

      3 years ago

  • avatar
    James Sukias

    I wouldn’t be surprised if tourists are over-represented in crash data in many countries. From your analysis tourists are over-represented by 4.5/3.3=1.36 (36%). Is this high compared with other countries? Aside from the long distance tourists travel to get here, our roads are distinctly different, adding to risks to tourists (e.g. residential driveways on 100 km/h roads, highway overtaking on opposite side of road, and many roads with much higher speed limits than would be common at least compared with Europe). They also have double white lines to increase the distance between oncoming traffic, although I note the increased use of wide flush medium between oncoming traffic in NZ. As pointed out by my Dutch colleague, tourists tend to travel much longer distances per day than would be average for residents (your point about road miles), but conversely, drivers who are uncertain where they are going often are a cause of road hazards either by traveling slowly, or by poorly signalled turns when they suddenly realise a need to turn.

    3 years ago

    • avatar
      Thomas Lumley

      You’d certainly expect tourists to be over-represented, and that’s what the data suggest.

      My point is that even an intervention that managed to completely remove this over-representation of tourists would have a very small effect on the road death toll — they aren’t hugely overrepresented, and they are a small fraction of the population.

      3 years ago

  • avatar
    James Sukias

    True. Also the “over-representation” may be lower than in my simplistic ratios, due to the higher distances tourists tend to travel.

    My point about comparing tourist in NZ v. Overseas was to see whether NZ roads are truly a factor (as suggested by some), for our road toll.

    3 years ago

  • avatar

    Lianne and I are both of the opinion (based on anecdotal evidence only) that NZ drivers are far more aggressive than California or NSW drivers. We looked up some accident statistics and things seemed roughly comparable, but maybe we missed something. Do you know (or know where to find out) where NZ’s road injury rate per km sits with respect to other western countries?

    3 years ago

    • avatar
      Thomas Lumley

      There’s a list of death rateson Wikipedia, including rates per billion vehicle-km. It’s mostly OECD or WHO data.

      New Zealand is high: about 10% higher than USA, and nearly 60% higher than Australia.

      3 years ago