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Adding Roads Causes More Traffic

https://www.citylab.com/transportation/2018/09/citylab-university-induced-demand/569455/

This article talks about how the idea of constructing new freeways and adding lanes to existing highways for the purpose of reducing congestion and travel times actually backfires and increases congestion and travel times. This phenomena was briefly discussed in class with Braess’s Paradox, which states that’s adding one or more roads to the road network can end up making the over all traffic flow worse. It logically makes sense that adding more area for traffic to pass through would alleviate congestion however, it creates induced demand: the larger the supply of something is or the cheaper it is, the more likely people are to use it. Applying this to road networks, the more lanes that are available, the more people will use them which creates more traffic than there originally was. The article provides an interesting comparison of traffic. Instead of thinking of traffic as a liquid which requires a certain amount of space to pass through at different rates, think of traffic as a gas which will expand to fill any space that it is given.

The article also discusses different payoffs that travelers have to assess before they decide which mode of transportation to use. These payoffs encompass travel time, price, and convenience. When new lanes are added or new freeways are created, people assume that travel times will be faster, so they may now decide to drive instead of use public transportation like a bus or train because when weighing travel times they now believe that driving a car will have a better payoff. Furthermore, roads with tolls on them may discourage people from driving on them because now the payoff is worse than toll free roads or public transportation because now driving has added expenses. Similarly, having to pay large amounts for parking also discourages people from driving because of another added expense making the payoff worse.

One specific example that is used is the 405 in Los Angeles. $1.6 billion was spent to add a northbound carpool lane and new on and off-ramps. Construction lasted five years and once it was completed, it was determined that the average travel time going north, the direction with the new lane, was actually a little longer than it had been before the costly renovations. Ultimately not only did the new lane fail to alleviate the traffic, it actually caused more just like Braess’s Paradox states.

Some novel ideas have been presented in order to truly reduce traffic congestion. One idea is freeway removal, which would encourage more people to use alternative methods of transportation like they were before new freeways had been constructed. Supporters of this idea see a payoff in freeway removal being cheaper than fixing existing roads and increased use of other modes of transportation as better for the environment.

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