Double diamond interchange lauded
Popular Science magazine named Missouri’s first diverging diamond interchange in Springfield one of the 100 top innovations of the year.
The interchange is the model for one, above, that is planned at Interstate 270 and Dorsett Road in Maryland Heights.
The Springfield, Mo., interchange opened in June at Route 13 and Interstate 44. By forcing traffic to crisscross to the left side of the road before the interchange, the configuration allows cars to make left turns onto highway onramps without crossing oncoming traffic lanes.
The Federal Highway Administration said the diverging diamond configuration permits 600 left turns onto the highway per hour per lane. That’s twice the rate of a traditional interchange. Motorists are guided through the interchange by a series of signs, pavement markings and concrete islands.
To see the Popular Science article, go to: http://www.popsci.com/bown/2009/product/diverging-diamond-interchange
To learn more about MoDOT’s Springfield interchange, go to: http://www.modot.mo.gov/springfield/major_projects/Greene/I-44andRoute13.htm
Wow!
At first I thought the map made it look like folks were driving on the wrong side of the road. I would like a wider view map that lables some of the other streets on the map (on the outer edges of the project) so I could picture how large this is going to be.
This really is a cool intersection design. I wish I were a transportation engineer in another life. One of the great benefits is because of the free left turns, the stoplights are only in a two-phase operation instead of the usual three or four phases.
I would appreciate seeing a slightly more detailed diagram showing which movements are signalized and how the phases work. From what I understand, the movements onto the major highway are never signalized (that being the whole point of this type of intersection). The left turns exiting the highway are usually (but not always) signalized, while the right turns off the highway are occasionally (but less frequently) signalized as well.
I hope signs will be included to tell people which lane to be in to go northbound or southbound on 270. If you’re used to the idea that you always stay in the right-hand lane to go north *or* south, this will be confusing.
The design has drivers criss-crossing at traffic signals, giving left-turning vehicles a free left turn onto the intersecting roadway while other drivers can continue more easily through the interchange.