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A promise to ease traffic, and why it won’t work

NPR has an article with a nice flash based widget detailing a new traffic pattern in Missouri where Missouri 13 meets Interstate 44.  The new pattern is called a ‘Diverging Diamond‘, and the goal of the whole deal is to make it easier for cars to transfer from one road to the other, without causing a traffic stirr. At first, I thought it was great.  It’s different!  And, you don’t have to wait for the turning traffic to finish at the light before it turns and lets you go straight (or vise-versa).

Now, let me tell you why this won’t work, at least in most cases.  It may very well work for this particular interchange, but if your state highway commission decides to do the same at the interchange you dread the most, I wager there’s at least an 85% chance that it could make things worse.  The reason why, is because of the traffic merging into the same lane as other traffic is exiting from, and there not being a merge area here.  Furthermore, because this is the ‘fast’ lane, you clog up the pipe more easily; more traffic flows in the left lane than the right.  Lastly, the area which can be used to merge (even if there was a merge lane), is just too small.  If there is a traffic situation in the first place to warrant such a measure, there should be a large merge area.

Here’s an example scenario, assuming a moderate traffic situation.  If a big-rig, an 18 wheeler if you prefer, comes off of I-44, cars in the left lane will have to slow to allow it access, or the 18-wheeler will cause traffic to build up on the ramp, cascading back on to I-44.  If the big-rig makes it on to MO-13, the traffic in the left lane would have slowed, which over a rather short period of time, could cause a backup at the light after similar occurrences.  This backup at the light will then cause backups for both east and west bound traffic.  What may also happen, is traffic slows in both lanes, as some other vehicle merges over to the right lane, attempting to avoid the situation caused by the tractor trailer.  This could easily cause backups at both lights, as the expected volume of traffic does not make it between lights, and causes a cascading back-up from one light back to the other.

In short, traffic will always be bad, unless roads are designed to ferry twice the load they ever will.

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Posted in Cars.

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