Speed Kills......

Clearly not or there would be F1 drivers with their heads exploding when they reached the magic speed at which it killed you. So as we all know it is the abrupt stop at the end that does the damage, however this safety message has and continues to be drummed into us and frankly I am sick of it. In my view it is a simplistic and boneheaded answer to a far more complex problem.

So lets examine the question does the average driving speed increase the rate of driving deaths.

Of course running experiments to prove or disprove this point is problematic however there are some natural experiments that we can look at. One of which is the experience of the United States. During the oil shocks of the 70’s the US Federal government took over the setting of speed limits to aid in lowering fuel consumption. The older members of the audience will recall that the government here also lowered the speed limit at that time for the same reason. After the oil price settled down the Federal government passed this function back to the individual state governments who then set a range of speed limits. So how do the states compare to each other?

Well here is the table of results and asking Excel to Correlate the Deaths per 100,000 with the speed limits it calculates a correlation of 0.21 or in other words no correlation of any statistical significance. Also if you look at Hawaii at 6th lowest with a low speed limit and death rate but then Utah with the highest speed limit is only 8 places higher. And there are 5 other states with higher speed limits lower than Hawaii. So clearly there is other stuff going on here, some of which might be obvious such as New York which encompasses New York City where there are a lot of people but no one drives anywhere much . But we know that California is the driving capital and with a speed limit of 70 and 9th on the table it is doing well. New Zealand also included is very mid table and 2008 was the best road toll NZ had had for 30 years.

Double click to enlarge

So let’s look at a New Zealand experiment in 1985 the government raised the speed limit from 80kph to 100kph. At this point let me remind you of the world’s most famous physics equation E=MC^2 with the important bit for us being the C squared bit C equals velocity or speed in our case so the impact of an accident with the 20 extra ks is exponentially worse because of the squaring. Eg 1000kg vehicle hits at 80 kph equals 6,400,000 energy units where as at 100kph it is 10,000,000 so a 50% increase in the severity of the crash. So there should be a massive increase in deaths as a whole bunch of survivable crashes suddenly become 50% worse. So what happened well 1986 did show a spike in deaths (nowhere near a 50% increase) but in 1987 and subsequent years it showed a decline which is now an established trend, so despite a 50% increase in potential road deaths are falling. So much for Speed Kills.

In doing some research for this I came across this page http://www.socialreport.msd.govt.nz/safety/road-casualities.html
It shows an increased mortality for Maori in road deaths of twice the rest of the population, why this should be so is of interest as it may reveal something the rest of us could learn from. I doubt that Maori as a population drive on average any faster than the rest of us so I bet it isn’t speed that is killing them (my pick is because Maori, as a group, are worse off economically it is because they drive worse cars) so rather than handing out more and more speeding fines how about we look for the real causes.