Traffic in a Directed Network: Removing Highways Eases Congestion

A highway is, in theory, designed to funnel traffic to and from destinations as efficiently as possible.  During the mid to late 1950’s construction on the Interstate Highway System in the United States began and the suburban population began to boom.  Highways sprung up all over the country allowing people to live outside cities and commute into the urban areas for work.  These highways were created with the intention of making people’s commute easier and quicker but as time has passed it has become apparent that highways actually increase congestion. Not every highway is inefficient or susceptible to major congestion because many simply connect different areas without the interruption of intersections or traffic lights.  Highways are an efficient way to travel long distances without knowing the area specifically.  The problem becomes more apparent when the highway continues closer to the more populated city because as population increases so does traffic volume.  When the highway goes directly through a major city the traffic congestion becomes an absolute nightmare during peak hours or in the event of a road accident.

Induced demand is the principle that explains how as the supply of a good increases the consumption of that good will also increase.  In this case, highway access is the good and as more people gain access to a highway they will opt to take it rather than side streets.  When a highway dissects a major city drivers are encouraged to make use of it which leads to gridlock traffic and increased pollution.  Congestion and pollution are an unfortunate by product of a highway system but it’s the loss of public space and physical separation of city neighborhoods that is leading many cities around the world to dismantle and repurpose their existing highways.  Some cities choose to reroute their highway underground in tunnels and others remove them entirely.  The results show that without the option to easily access a highway commuters drive on side streets, spreading the volume of traffic across many smaller streets.  Public transportation systems also become a more realistic option for some commuters which decreases the total volume of traffic as well.  When a highway is eliminated or rerouted the space it previously occupied becomes available and can be repurposed for public use or commercial and residential development.  Attached is an article posted on Gizmodo on the subject with six examples of cities that saw various positive benefits following the removal of outdated and inefficient highway systems.  Some of the projects highlighted in the article are recent, others are in the past and some are still being proposed but each example gives a visual representation of how much impact a highway system has on a city and how the removal can benefit a population.




2 thoughts on “Traffic in a Directed Network: Removing Highways Eases Congestion”

  1. Do you think that even with the congestion from the highway that travel times are still significantly shorter? I know you mentioned back roads, but I feel that in many instances, the congestion that occurs is more of an inconvenience rather than a problem. Even though using a highway may save thirty minutes from a trip, as opposed to using the back roads, some could argue that sitting in traffic makes it seem longer. relating this back to class with the example using the guaranteed 45 minute commute for each path compared to the one that depended on how many people use the road, I feel that highways have become closer more of the prior. Commuters take into account that the highway takes a certain max amount of time, regardless of the traffic, and anything quicker just adds value to their experience. Like you mentioned, spreading the traffic among the many roads may make travel times faster, but it would be interesting to see if commuters would chose the risk of not taking the highway over the guarantee of a certain travel time.

  2. I found this interesting, as well. But I feel that part of the reason taking back roads can shorten travel time is because people are using the highways. I agree with the necessity of expanding our travel options–the article mentions making way for bike paths; people could walk, run, or bike where they need to, but I think there is still a necessity for highways like I-95. Unless, the city campaigns for more non-motor vehicle travel to cut back on the highway traffic. For example, parking lots closer to the city, where people can part their cars and bike to where they need to go. The streets can be widened to include bike paths and this would definitely encourage that mode of transportation. It is a similar idea to what they had done when building the new 202 bypass, just (if done in the city) would allow commuters to get from point A to point B more easily.

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