- Adding a new traffic land via the Salt Lake Tribune

    Does Adding an Extra Driving Lane Make Traffic Worse?

    Counterintuitively, adding extra driving lanes can actually lead to an increase in traffic congestion!

    2y ago

    37.1K

    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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    Comments (12)

    • Here in the US, the biggest issue is people who just hang out in the left lane. I can't count the number of times I've been stuck in congestion, just to find out that there are 4 cars driving 45mph NEXT TO EACH OTHER. They need to have their license revoked. If it truly is a privilege and not a right, then these people do not deserve that privilege.

        2 years ago
    • Here in the UK they are adding extra capacity by turning the hard shoulder into an extra lane which is fine until there is a breakdown, then chaos or worse ensues, there are accidents daily on a recently opened stretch near me in Derbyshire.

        2 years ago
    • The amount of drivers who hang in the fast lane (UK- the rightlane), (Canada the leftlane) is annoying when the other lanes are empty. Then they get close to their chosen exit and cut straight across all three lanes chopping up everybody because they think they have the right to do it. When I took my test in 1980 my instructor taught me to position the car to the nearside way ahead of the planned exit . Its just bad driving in both instances and its even worst when you see them on the phone !

        2 years ago
    • My consistant question in seeing additional lanes addednis how far up the motorway that new lane extends. A roadworks adding three new lanes to what was once a two lane road has homes and businesses on either side. Monetary issues only allow for so much new asphault. So the choked lane problem is just being moved deeper into the community.

      Another issue is driver training. Why is it neccessary for the far left lane (fast lane) to be choked up to a standstill while it is the far right lane afflicted with off ramps stopped cold with stop lights and community confestion. Shouldnt the left labe be free of congestion? I chock it up to poor driving skill.

      There are facinating new designs that apparently could alleviate these problems. But what district has the funds to create them?

      The hammer in the ape's hand is the autonomous cars. While they are the future, I find it discouraging that sites like this and enthusiasts magazines tout the tech as *cool*

      Indeed it is, but as a purist, Id rather be in control. Google wont know how to get the most enjoyment out of an apex. Ya know?

        2 years ago
      • However, with traffic congestion, there is no enjoyment in an apex....not on your average road these days, so that point is moot. Let the autonomous cars handle the heavy duty traffic and save your driving for the track or those twisty...

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          2 years ago
      • Ron, you make a valid point. However, here in the Golden West where the Toyota Prious is *hot* -Paris Hilton quote- the wages of progress is to legislate old ways out of existance. Once autonomous autos are deemed reliable, personally...

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          2 years ago
    • The logic in the article suggests that adding lanes increases traffic. That of course is irrefutable. More capacity invites more use in particular when there is a higher demand. The solution for congestion within this logic is to remove all roads. This will not only instantly solve the issue but also annihilate the economy bringing demand to zero also.

      That just show that the wrong root cause is being adressed. Encourage long distance traffic over water and railways and guide the knowledge economy to run via internet and demand also takes a dive without having to touch the roads.

      It's not the roads. It's not the cars. It's the peak demand.

        2 years ago

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