2006/11/14

Unsafe statistics

First, I am wholeheartedly in favor of "an ambitious campaign designed to place Dubai among the top 10 international cities with safest roads within the next five years". But it isn't going to happen with analysis like this: "Taxi drivers are most likely to cause a fatal accident".

The proof that taxi drivers are the most dangerous? "Taxis represent [slightly] less than one per cent of all vehicles in Dubai...However, during the first nine months of this year, taxi drivers caused the deaths of seven people. The total number of deaths for this same period is 215 people, which means taxis were responsible 3.26 per cent of the road deaths."

But you can't just take the number of taxis and the number of registered vehicles and compare them to the number of fatalities. Let's look a little deeper.

The story also says that taxi drivers are on the road up to 16 hours a day, 7 days a week and drive 400 to 500 km per day. Let's use 12 hours a day/84 hours a week as an average for the taxi drivers of Dubai, as the story suggests. So for taxis to make up less than 3.26% of the cars on the road, the other 600,000 - 700,000 cars of Dubai would have to be on the road an average of 22 to 26 hours a week on the road. Now, I know that traffic in Dubai is bad, but does it seem likely that there are 600,000 non-taxis on the roads of Dubai 26 hours a week?

Or let's look at kilometers driven. The story suggests 2800 kms per week as a low figure. Unless the average kilometers driven per week of the other 600,000 cars is about 944, then taxis drive more than 3.26% of the kilometers driven.

Moreover, even if the government had just banned taxis starting January 1, there would still be at least 208 deaths on the road. If the authorities and Emirates Today are serious about making the roads safe, then reducing the number of hours taxi drivers work, as good an idea as that is, is not going to make dent in the fatalities.

2 comments:

Seabee said...

Exactly right. It's another one of the simplistic misunderstandings of statistics that we get all too often.

The real danger is that policies and laws will be based on these misreadings of the real situation - which I suspect happens very often, given the appallingly bad planning that's all around us.

oink oink said...

Exactly right? Exactly. But taxis aren't about to be banned just yet.

These aren't just statistics. These are the children born when Statistics married Damn Lies.

Another something to get used to in the Emirates.