Friday, October 26, 2007

National Safety Stats on Light Rail

Often, when NIMBY forces are pushing against a proposed transit project, there is usually one argument that the rail opponents rally around. Many times these arguments are red herrings, but every now and then the opposition is on to something.


In the case of the Expo Line, the local opposition has rallied around the idea that light rail is a dangerous form of transportation, especially for local students around schools other intersections. Opponents to the Expo Line argue they have the stats to back up the idea that light rail would be a literal killer in the community. Supporters of the argue that the stats say the opposite.


So what do the stats say?


At first glance, it appears the opposition has a point. The USDOT’s Bureau of statistics shows that in 2004 (the most recent reporting year) light rail related fatalities occur at double the rate as commuter rail and almost 10 times as much as bus related deaths. In 2004, there were 22.4 fatalities caused by accidents related to light rail for every 100 million vehicle miles traveled in America. There were only 14 recorded light rail related fatalities, but there were less than 100 million VMT’s, which is a federal standard for measuring VMT, for light rail! There were 2.6 deaths per 100 million miles for bus and 10.1 deaths per 100 million miles for commuter rail.
But, as Mark Twain had long ago noted, statistics can lie.


First off, suicide by light rail seems a popular way for someone to end their lives. If there are federal statistics that remove suicides from the total number of fatalities "caused" by light rail I haven’t seen them for recent years.


A quick google search shows that of the fourteen light rail related fatalities several were suicides.


(July 23rd article, one light rail related death a suicide)


(one suicide in San Francisco area)

As a matter of fact, the Federal Transit Agency didn’t count suicides in death counts until 2002. Not surprisingly, fatality rates jumped from 2002-2004 from 8 fatalities to 14. From 2000 to 2002 light rail related fatalities had dropped from 22 to 8.


Secondly, the popular usage of fatalities divided by vehicle miles traveled is a poor equation to compare the safety of various transit modes. Light rail, unlike other forms of rail and bus service, runs near exclusively in urban areas. These areas have the densest populations and are most likely to have accidents occur. To do a better comparison, one would have to look at only the fatalities caused in bus or heavy and commuting rail in urban areas with only the urban VMT’s.

While VMT is a popular way to measure safety, we can get a different picture by looking at fatalities per passenger mile traveled. See the following chart by the National Transit Database.


The chart doesn't only show that light rail isn't always the "most fatal" form of transit, but also that the fatality per PMT rate was plummeting before the FTA decided to count suicides the same as other accidents.

A last problem is small sample size. Because we’re dealing with such a small number of fatalities (14 people died in light rail related incidents in 2004 versus a population of over 300 million people), the data isn’t reliable because of a small sample size.


Because the data isn’t as reliable as we would like, I suggest that instead of focusing on light rail as a mode in and of itself, that the safety debate be put on hold until after we have a final design to analyze.

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