The first time I saw the plan, I remember thinking, “this is really slick.” The plan was for a diverging diamond interchange, the kind of interchange that is about to be completed on Route 59, where it crosses I-88. The “complete streets” crowd hates it, but I think the motorists are going to love it.
The primary goal of the interchange is to eliminate those left turns that cross oncoming traffic. Essentially, the right and left lanes cross over and exchange places. Those cars wishing to turn left can then peel off down a ramp without stopping. Then the lanes cross over again, so that the right is once more on the right and the left is on the left.
Drivers who want to turn right can peel off before the lanes cross over the first time. Cars merging from the right can do that after the lanes have gone back to their original positions. The lanes remain crossed just long enough to allow the cars exiting left to do so.
Obviously, because the lanes cross each other twice at the same grade, traffic can’t flow on both at the same time. Banks of traffic lights stop one lane while the other uses the crossovers, then lets the other lane go.
There are other configurations, sometimes called braided versions, that allow the lanes to cross over and under each other, but these of course are very expensive, and it is not clear that they save any more time in the long run.
This weekend, the interchanges with I-88 at Route 59 are closed so the project can be largely completed. They will remain closed until 5 a.m. Sept. 21, if everything goes as planned.. So what can we expect when this remarkable interchange is finally completed?
Some predicted complete chaos, with confused drivers smashing into each other in all possible ways, but that doesn’t appear to be the case. The most feared accident was one in which a befuddled driver failed to cross over, and drove into incoming traffic.
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In computer simulations using drivers of all ages and skill levels, however, that never happened. Never. Cars still rear-ended each other, and did a number of silly things, but with longer yellows at the two banks of signals, and an essential all red interval, accidents should be at least 20 percent fewer, and perhaps many fewer than that.
The first of these kinds of interchanges in the U.S. was apparently in Springfield Mo. in 2009, and those folks are absolutely giddy with delight about its success. Traffic along the Kansas Expressway, where it crosses I-44, used to back up for miles. Now, at worst, it’s a “little congested sometimes.”
So the big advantages are apparently an increase in capacity and a big decrease in delays, both welcome improvements along Route 59, which many people don’t use unless they absolutely have to.
It could take a while to get the signals timed right, and I’m sure many drivers are going to be confused and upset about the new interchange. There should probably be an extensive public education program, but I don’t see that happening. Follow the signs and good luck.
However, the largest groups to object to this type of interchange are sure to be pedestrians and bicyclists. I don’t know how many of them use Route 59, because I sure don’t, but no matter how the interchange is configured it’s going to appear formidable, threatening, and basically unusable to them.
I’ve been told they can be accommodated. I kind of doubt that. On the other hand, I am much more concerned about achieving “complete streets,” streets everybody can use equally, downtown. That should be our priority. On Route 59, our priority should be to get out and patronize the poor businesses that have been all but shut down during this construction. They’ve suffered enough.
Bill Mego is a freelance columnist for the Naperville Sun.