Road Engineer's Confession Reminiscent Of SE Freeway Expansion Rationale
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Posted by James Rowen at 6:24 PM
In that post, Charles Marohn links to (but does not name) an influential article by Eric Dunbaugh that blew the lid of classic road engineering. Dunbaugh's research shows that designing for speed through 'geometric engineering' in order to support vehicle speed alone, while accounting for safety only by establishing an enormous 'clear zone' on the side of the road, has instead lead to more accidents, rather than fewer. That default design also damages other street functions, such as retail activity, social cohesion and levels of use by residents and pedestrians.
Turns out drivers respond to objects near the road by slowing down; in the absence of activity or objects in the streetscape area and roadsides, drivers ignore posted speed limits and drive as fast as they (incorrectly) perceive to be possible on the too-wide roads.
The result is more accidents and less safe traffic, a phenomenon running counter to conventional road engineering practice. In many cities folks are regularly killed because the design flaws don't take into account multiple goals or multiple modal users.
Madison, for example, uses main streets in retail districts as regional arterials, undermining the economic vitality of the central city and undercutting the their responsiblity to residents to invest in safe road designs with traffic-calming or basic streetscape enhancements.
The refusal to get up to date has badly damaged the city, hampering Madison's ability to retain creative talent, attract investment and precluding in the process its attempts to earn Platinum status as a bike-friendly city.
This is pretty basic stuff at this point, and Madison's fallen way behind the best thinking in the field. Staff and political leadership resist state-of-the-art techniques and are virtually intransigent when it comes to adopting best practices.
It's disappointing. And the attitude stands as a self-imposed ostacle to creating a 'green capital city' -- or an economically vital city presumes to take its cue from New York (which has adopted these techniques). Uncomfortable, maybe; but accurate.
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