View Single Post
  #2 (permalink)  
Sat, May 16th, 2009, 08:22 am
bwilson4web bwilson4web is offline  
 
Looking at the 2007 accident data, the NHTSA report DOT HS 810 993 covering 2007 fatal accidents, and the Prius sales history, I did a 'back of the envelope' analysis to compare "miles per pedestrian deaths" for all vehicles and the Prius:
  • 554,000,000 miles per pedestrian death, all vehicles (~4,700 NHTSA)
  • 1,023,000,000 miles per pedestrian death, Prius (~7 deaths)
Now there are a lot of variables that are not accounted for such as vehicle weight (lighter ones are less deadly,) speed (urban vs rural), and other factors. Also, we are looking at very small numbers of deaths, 7 associated with the 6 Prius pedestrian accidents. But I wanted to look at a worst case scenario. What is the worst case rate of Prius-pedestrian accidents.

The model I used started with the Prius sales per year minus 5% loss per year and 15,000 miles per vehicle per year:

YearSalesRunning in 2007miles/year
20005,5623,88458,260,000
200115,55611,435171,525,000
200220,11915,567233,505,000
200324,62720,058300,870,000
200453,99146,290694,350,000
2005107,89797,3771,460,655,000
2006106,971101,6221,524,330,000
2007181,221181,2212,718,315,000
477,000 Prius on USA roads in 2007
7,162,000,000 Prius vehicle miles in 2007
6 pedestrian-Prius accidents in 2007
7 pedestrians in the accidents (actual pedestrian fatalities may be less)

1,023,116,000 miles per Prius vehicle per pedestrian deaths in 2007 (approximate)

1.64 fatalities per 100 million vehicle miles in 2007 (NHTSA report DOT HS 810 993)
60,975,610 miles per all vehicles per fatality in 2007
11% the number of pedestrian deaths of all fatalities

554,324,000 miles per all vehicle miles in 2007
This 'back of the envelope' data can not be used as an exact metric of relative risk. Variables such as vehicle weight, urban vs. rural, and other aspects have not been factored. A proper multi-variable analysis is what the National Highway Traffic Safety Administration should do. But based upon these and Dr. Christopher Hogan's 2008 report, the Prius appears to have no detectable, higher risk to pedestrians.

Bob Wilson

Last edited by bwilson4web; Sat, May 16th, 2009 at 12:53 pm.
Reply With Quote