June 3


The Federal Highway Administration (aka FHWA) has a report out on driving trends in the United States.  For the first time in 25 years, traffic is decreasing instead of increasing.  Americans drove 688.7 billion miles during the first quarter of 2008 compared with 704.9 billion miles during the first quarter of 2007.  This is a 2.3% decrease in traffic.  The chart below is from the last page of the report.  It shows monthly traffic trends over the last few years. 
Traffic chart_Page_10
This is an important trend for traffic engineers to study.  In small scale traffic studies, we typically use a growth rate to project current traffic volumes to future traffic volumes.  The growth rate can be based on population growth, traffic growth on specific roads, or traffic growth within the city or county.  This background growth is usually significant if the engineer is projecting traffic out 10 to 20 years.  If you are a developer financially responsible for improvements based on these projections, I recommend you look closely at the assumed growth rates and discuss our current trends with the traffic engineer.  As the financial industry constantly points out – past performance is no guarantee of future results.  This is especially true in traffic studies making projections based on traffic growth from the housing boom of the last decade.

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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