1.0Sightline Institutehttps://www.sightline.orgClark Williams-Derryhttps://www.sightline.org/profile/clark-williams-derry/Study: More Roads = More Traffic - Sightline Instituterich600338<blockquote class="wp-embedded-content" data-secret="nf6Ub5PYUF"><a href="https://www.sightline.org/2011/12/14/study-more-roads-more-traffic/">Study: More Roads = More Traffic</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="https://www.sightline.org/2011/12/14/study-more-roads-more-traffic/embed/#?secret=nf6Ub5PYUF" width="600" height="338" title="“Study: More Roads = More Traffic” — Sightline Institute" data-secret="nf6Ub5PYUF" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script type="text/javascript">
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https://www.sightline.org/wp-content/uploads/2011/12/road-flickr-user-Cyril-Plapied.jpg500333Today's news carries a story that I've been expecting for a while: "Connecting Washington," a task force convened by Washington's governor, has called for $21 billion in new transportation investments over the next 10 years. I haven't seen the recommendations, only the news reports. But it looks like the money would get spread around a bit---with some for ferries and some for transit---but most of it is for roads. In the upcoming months, I expect we'll be hearing a lot about how road investments will help clear up traffic problems, particularly in greater Seattle and the Washington side of the Portland metro area. But this study---which I count as single most interesting transportation paper I ran across all year---suggests otherwise. It's a careful and remarkably thorough analysis of the relationship between urban highway space and traffic volumes, and its key finding is straightforward: For interstate highways in the densest parts of metropolitan areas we find that vkt [Vehicle Kilometers Traveled] increases in exact proportion to highways In short, the authors find that building new urban highways simply increases traffic volumes---not in some general, intuitive sense, but in the sense that a one percent increase in urban highway space increases urban road travel by precisely one percent.