For every 1 minute of travel time saved by speeding, roughly 2.5 minutes of human life are lost in speeding-related accidents
This stat is from a prior post, the cost-benefit trade-off of speeding. Here is an explanation of how I reached those figures, along with some more thoughts / facts about the science of speeding.
These numbers are based on two separate calculations.
- How many years of human life have been lost in speeding-related accidents?
- What is the total amount of time Americans have saved by speeding?
1. Estimating the loss of life in years
To estimate the amount of life lost due to speeding-related accidents, I looked to the Dept. of Transportation’s FARS (Fatality Analysis Reporting System) database, which records every fatal traffic accident going back to the 70’s, including detailed information about every vehicle and each individual involved.
Looking at the last 10 years of available data (2004-2013), I identified all the individuals who died in accidents where speeding was flagged as a contributing factor. There were about 115,000 of them, roughly one-third of all traffic fatalities. For comparison, alcohol was a contributing factor in about 124,000 traffic fatalities.
116k individuals have lost their lives in speeding related accidents, 2004-2013
To estimate the years of life lost by each of these 116,000 people, I used life expectancies published by the SOA.
The FARS dataset includes gender and the exact age of each individual at the time of death, so each one can be matched up with a fairly precise life expectancy. Summing the life expectancies of all 116,000 individuals over the 10 year period, the total comes out to about 5.2 million.
From 2004 to 2013, 5.2 million years of life were lost due to speeding-related accidents
2. Estimating the amount of time saved by speeding
To estimate the other side of the equation, the total amount of time saved by speeding, I started with the Dept. of Transportation’s HPMS (Highway Performance Monitoring System) data, which includes an estimate the number of annual vehicle miles traveled in the U.S., broken down by type of road (e.g. freeway, state highway, local road, etc). For each type of road, I assumed an average speed limit, which is somewhat arbitrary. But in the end it doesn’t make much difference for the final calculation.
Based on total number of miles driven and the assumed speed limit for each of those miles, I calculated the total driving time if everyone drove exactly at the speed limit. That number comes out to 84,120,493 years.
To see how that number changes when people speed, I used the data from this report by the Insurance Institute for Highway Safety. Here are the figures from their report in terms of variation from the average speed.
In rough terms:
- 10% of vehicles drive at least 5 mph faster than the average traffic speed.
- 5% of vehicles drive at least 10 mph faster than the average.
- 1% of vehicles drive at least 20 mph faster than the average.
These figures are consistent with other reports that have estimated speeding behavior. Assuming these rates of speeding, the total time that Americans spent driving drops to 82,545,028 years. (vs. 84,120,493 years if everyone drove at the speed limit). The difference is 1,575,465 years. Then to account for the presence of passengers, I multiplied this number by 1.38 (0.38 is the average number passengers per vehicle).
From 2004 to 2013, 2.17 million years of travel time was saved by speeding
5.2 million years in life lost vs 2.17 million years of travel time saved is a ratio of about 2.5 to 1, the stat quoted at the top.
Here is the original post about these figures: The Science of Speeding
If you feel like digging into numbers yourself, the data is posted on the get the data page.
Primary data sources:
- Dept of Transportation FARS database
- Society of Actuaries life expectancy tables
- Highway Performance Monitoring System
- Insurance Institute for Highway Safety
More about my background
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