January 27, 2013
Traffic Engineers Getting Wild
This Atlantic Cities article covers some innovative intersection designs that are intended to reduce theoretical conflict points - at least for cars. These don't really seem to be intended for use in urban environments.
Nonetheless, at least one "diverging diamond" example has been built with at least nominal accommodation for pedestrians and cyclists. Chuck Marone (of "Strong Towns" fame) dissects it somewhat mercilessly in this YouTube video:
January 28, 2013 12:35 PM
Aaron Hall Says:
Setting aside the absurdity of calling this "pedestrian-friendly", I see nothing about the diverging diamond design that is in any way better or easier to navigate than a standard diamond interchange. It's adding a layer of complexity where none is needed, but still has as many signals as a regular diamond. Looks like too many engineers trying to be clever for clever's sake.
January 28, 2013 1:48 PM
The idea behind the "diverging diamond" is that it is decomposed into a set of intersections for which two traffic phases will suffice. Whether that makes it better (for motorists) is another matter. Clearly, the diverging diamond is a nightmare for pedestrians to navigate.
January 28, 2013 5:45 PM
Chris Smith Says:
It also seems to require a lot of real estate!
January 28, 2013 8:38 PM
The diverging diamond is a great solution to the problem the engineers were presented with, and from a pedestrian point of view presents no more or fewer conflict points than a regular dual signal diamond interchange. All of the points you made in the video can be made about any diamond interchange. The issue here isn't the engineers. They simply solved the problem they were given: Make the traffic flow smoother and safer, and ensure pedestrians and other users were given an equivalent or better environment then before. The issue lies with the planners and politicians who promoted development that leads to this kind of design. The Diverging Diamond isn't the problem, the surrounding area is.
January 29, 2013 4:40 PM
Ron Swaren Says:
And I heard today that a group of engineers now wants the Oregon state capitol building to have $75 million of upgrades.
-David Evans and Assoc.---big CRC beneficiaries. now they are getting behind the high speed rail boondoggle, thanks to Eugene lib. mayor Piercy. ( I saw one of their vehicles at an ODOT open house.)
-Engineers at the state capitol looking for $75 mil. project
-ODOT engineers whining for statewide seismic upgrades
Is this government for the people---or the engineers?
January 30, 2013 10:31 PM
Peter Koonce (@pkoonce) Says:
The diverging diamond is a terrible concept from a pedestrian point of view. Let's just start with someone from the blind community trying to navigate this. Could you imagine trying to navigate such an intersection? I could just imagine my 9 year old walking on the street knowing exactly what to do.
The crossing also requires crossing at angles to traffic that are much different than typical.
Urban diamond interchanges can be designed poorly too, but the diverging diamond almost requires a free right turn and forces so many crossings.
Cycling through a diverging diamond at night would be fairly confusing as well. There are no cycling specific facilities. I am surprised the commenter on the video actually gave the engineers a pass on the "facilities".