- Adding a new traffic land via the Salt Lake Tribune

Does Adding an Extra Driving Lane Make Traffic Worse?

2y ago

27.5K

I’m sure that everyone has had that thought while stuck in traffic, “Why can’t they just add another lane?” It seems perfectly reasonable to expect that by adding another driving lane, the ability to move traffic through the road would increase. Yes?

However, that is not what engineers and scientists have discovered. Counterintuitively, adding extra driving lanes can actually lead to an increase in traffic congestion that is greater than the relief the new lane provides!

Traffic in Los Angeles via Vox

Traffic in Los Angeles via Vox

Here is a great link to an article that was published in Wired back in 2014 titled, “What’s Up With That: Building Bigger Roads Actually Makes Traffic Worse”:

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For those of you that would like to see the raw data, here is an actual scientific paper titled, “The Fundamental Law of Road Congestion: Evidence from US Cities”: pubs.aeaweb.org/doi/pdfplus/10.1257/aer.101.6.2616

The phenomenon where increased road sizes actually increases traffic congestion is called Induced Travel Demand (ITD). What all this means is that simply adding additional lanes may not get you the decrease in traffic congestion you have been hoping for. In reality, the additional lanes will only pull more vehicular traffic to the roadway, thereby increasing traffic congestion in the long run.

Traffic via CAP

Traffic via CAP

In case you still don’t believe me, here is another document titled, “Demystifying Induced Travel Demand”:

sutp.org/files/contents/documents/resources/B_Technical-Documents/GIZ_SUTP_TD1_Demystifying-Induced-Travel-Demand_EN.pdf

Now, that’s not to say that a massive roadway upgrade across an entire city whereby all of the roads are increased in size simultaneously wouldn’t help. Such a program probably would decrease traffic congestion across the city for a time. However, in the long run the improved roads would boost population growth in the city and eventually you would be back where you started. What is really needed is a way to increase the ability of our existing roadways to handle more vehicle traffic per hour.

Roadway construction via CR Jackson

Roadway construction via CR Jackson

So what can we do to help decrease traffic congestion? Obviously, increasing the speed limit on certain roads will increase the flow of traffic (for roads that are already congested, this would have no effect). And since we all know that the increase of speed does not increase traffic accidents, identifying those roads that will benefit from increase speed limits is a good place to start. However, the root of most traffic congestion is another phenomenon called the “Traffic Accordion Effect” or “Traffic Wave Effect”. This is where every time traffic hits a stop light, the field of vehicles compresses into a tight group, only to expand again when the light turns green as drivers increases the space in front of them for proper stopping distance as speed increases.

Traffic Accordion via World News

Traffic Accordion via World News

The removal of 4-way traffic stops in lieu of free-flowing Double Crossover Merging Interchange (DCMI) systems and common traffic circles (roundabouts) will certainly help to reduce the number of stops a vehicle has to take in order to travel from point A to point B, thereby increasing throughput of the roadways. Spending money on these systems is a much wiser use of funds than simply adding additional lanes.

DCMI via YouTube

DCMI via YouTube

But the real solution, dare I say it, will be self-driving cars that do not need to “accordion” in and out every time they come to a stop, because they can link together via a wireless network so that vehicles in a given row can start and stop together without needing the additional space.

Self driving cars via Quartz

Self driving cars via Quartz

What do you think Nation? Should cities stop putting money into additional traffic lanes in favor of removing 4-way stops and adding free-flowing traffic systems instead? Or are we all doomed until self-driving cars finally become main-stream? And won’t that be like jumping out of the frying pan and into the fire? Perhaps we are just doomed, period.

Keep driving sober my friends!

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