Assuming an average combined speed of 65 km/hour (about 40 mph) gives us annually about 80 billion driving hours in the US, and with 40,000 fatalities this translates exactly to 5 × 10-7 (0.0000005) fatalities per hour of exposure. Neither the fact that traffic fatalities also include pedestrians and bystanders killed by vehicles nor the deployment of other plausible average speeds (say, 50 or 70 km/hour) would change the order of magnitude. Driving is an order of magnitude more dangerous than flying, and during the time a person is driving the average chance of dying goes up by about 50
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