Northside Strangler Interchange

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The US-31 Freeway project was largely complete within the metro a few years ago but since you may have noticed there has been some major growing pains. The "Northside Strangler" interchange as we are calling it is showing evidence of some poor design decisions made by engineers that designed the interchange.

INDOT Cost Cutting

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In a cost savings measure a decision was made to reduce the number of lanes on the connecting ramps from US-31 south to I-465 west to just one lane. This has had the effect of leaving a nasty merge situation which causes a terrible traffic snarl that has lead to fits of rage and people pounding steering wheels. At the same time The East to North transition has us scratching our heads as well as to why that connector bridge was not double laned as well. Why were the approach lanes not lengthened and the exit separated from the rest of the interstate better in order to avoid all the last minute cutting in and sudden lane changes. In both situations it is apparent that 3 lanes of traffic are trying to have to squeeze down into one and negotiate with one another to do this. In some cases this can be a recipe for disaster. It leads to dangerous merging situations, unsafe lane changes, speeding, tailgating, cutting in, tempers flaring and discourteous drivers.

3 Lane Weave

Looking at the southbound ramps to I-465 there are several factors as to why this design is so bad. First US-31 traffic (mainline traffic) has to EXIT from the freeway. Mainline traffic should never have to exit from the freeway. A freeway should not exit from itself that just doesn't make sense. Secondly Too much traffic has to cross over other traffic. There is a large amount of traffic entering from the onramp coming from 103rd street. This traffic is trying to merge across 3 lanes to the right while other traffic is trying to merge to the left. Gore Areas are too large. This encourages people to cross over the gore areas to get to where they want to go rather than waiting until the line is broken where they should ACTUALLY attempt to make their lane changes. These gore crossings only exacerbate the problem further adding to the gridlock. Driver behavior is also a factor. At a proper merge etiquette should dictate that you take turns and merge, one left..., one right..., and so on..., so that everyone gets to go and the vehicles behind don't suffer from gridlock. Unfortunately due to poor road design and selfish drivers there is gridlock at times here. The key is that better road design can alleviate what human behavior experts and attempts at social engineering cannot.

Conclusions

This leads to a couple of conclusions. A retrofit of I-465 to the west of US-31 to I-865 is long overdue. The road is substandard and deteriorating. Has a dangerous left exit, and not enough through lanes to handle the traffic volume that it is currently expected to carry. Before that can be done however, something needs to be done to address the design shortfalls of the Northside 31 Spaghetti Junction. The easiest fix is to extend the second lane down to I-465 and look at employing ramp meters to mitigate merging at this point. This is not a perfect solution but at least it will get traffic moving.