The Show Me state likes what it sees in the new freeway interchange design known as a Diverging Diamond Interchange. A congested intersection in Springfield, Missouri is vying to make history as the nation's first diverging diamond interchange (DDI). The $12.5 million project, which will convert the National Avenue-James River Freeway interchange to a diverging diamond design, is slated to begin this fall. Missouri is so bullish on the benefits of the DDI design that it has plans for three more.
Interest in the DDI is also growing in the Midwest. OHM, a Livonia, Michigan-based engineering advisory firm (owners of this blog!), has evaluated DDIs at two locations for the Michigan Department of Transportation.
One of the most compelling benefits of the DDI design is that it increases safety. It does so by eliminating left turns crossing opposing traffic. This can equate to as much as a 50% reduction in crashes. Here's how it works:
Drivers travel for a limited distance, then cross back to the traditional or right side of the road. This unconventional aspect promotes left turn movements and allows traffic to move from the freeway ramp to the intersecting roadway without ever turning across the path of opposing traffic. Traffic signals are installed at the crossovers.
Stephen Dearing, a professional traffic operations engineer with OHM, lists more benefits of the DDI:
▪ Moves traffic more quickly, because the number of places where traffic must stop is reduced.
▪ Increases capacity at an intersection, because the left turn lane/signal phase is eliminated.
Best of all in these financially challenging times, a DDI is typically cheaper than a conventional diamond interchange because it requires fewer lanes to provide the same capacity.
More about DDIs and how they work: http://www.ohm-advisors.com/ddi/index.cfm
0 comments:
Post a Comment