# TED Conversations

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## Driving a car is one of the safer things you can do.

The purpose is to challenge the perception that road accident risk is a high risk. It isn't. The talk "If cars could talk..." begins with the statement that driving is dangerous. The theme in this talk is common throughout popular media.

We are saturated with messages about how dangerous it is to drive. This is not true. The facts say otherwise. Hence my example that the fatality risk of using stairs is 100 times greater.

Rate of deaths from stairs = 56 fatalities per 100 million miles.
Rate of deaths driving a car = 0.56 fatalities per 100 million miles.

As the proposed title says "driving a car is of the safer things you can do" which runs totally counter to the common mis-perception.

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• #### Kai Demandante

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Jun 20 2013: To me, it seems there is some error in your statistics:
1. Cars will transport you much more distance in a time period then taking the stairs will. To clarify, if I drove for one hour in a car, I may travel 60 miles or more (maybe around 30 on streets I don't really know). But if I walked up and down stairs for an hour, I doubt I'd get anywhere close to even 10 miles. This point was just trying to show that you may reach 100 million miles in a car much faster than taking stairs and then it may be considered more dangerous.
2. People use cars much more than they use stairs, so it'd be hard to compare them with any statistic. For example, you may have to walk up stairs for work (like in The Office during Stairmageddon), but to get to work you'd have to travel several miles. This is again just showing you most likely will hit 100 million miles (or whatever distance or even period of time) in a car, before you hit that same distance or period of time taking the stairs.
• #### John Culvenor

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Jun 21 2013: Hi Karl,

Thank you for the contribution. Yes, the total distance is greater in cars but that is related to total risk not incremental individual risk.

For example in total playgrounds are involved in 320,000 times more injuries to 5-14 year olds than chainsaws. But that does not mean that a 10 year old is safer playing with a chainsaw than on a playground.

To know individual incremental risk - how dangerous is this for me given a set amount of use - we need to divide the total outcome by the total exposure. Hence the calculation that traveling on stairs - per unit of distance - for an individual is 100 times greater than driving a car.
• #### Entropy Driven30+

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Jun 23 2013: But dividing both cars and stairs by mile does not measure the risk by exposure, but by mile.
• #### John Culvenor

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Jun 23 2013: Distance is one form of exposure. It is the common exposure measure in transport and walking is a measure of transport.

Time would be an alternative.

For the time exposure comparison we need the ratio of the average speed of both methods. I think about 10:1 would be of the right order. Perhaps your trip computer measures average speed since new. Mine shows an average over 30,000 miles of about 25mph. Compared to say 2.5mph for walking - although probably a bit less on stairs - but close enough just for the sake of an order of magnitude estimation we have a ratio of something in the order of 10:1.

At that rate stairs are ten times more dangerous than driving a car per hour of use.

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