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Why Expanding Roads Fails to Reduce Traffic Congestion

10 points by NomNew

by dpark

3 subcomments

I have a lot of trouble believing the premise that road capacity is unrelated to congestion. Practically we know that road capacity is only increased when congestion reaches critical levels. We also know that there are some massive empty roads that no one magically came to fill (as shown on Top Gear). Anyone who has lived in an urban area knows that congestion increases over time, whether they add new roads or not.
> Overall, VKT in the US doubled from 1983 to 2003, from 7,700 VKT to 15,900 VKT for interstate highways. For major urban roads, a similar pattern occurred – VKT went up from 15,000 to 30,000. In the same time span, the number of lane kilometers of interstate highways remained basically constant, while on major urban roads, it went up from 3,800km to 6,500km.
I don’t know how someone can trot out this stat and then claim with a straight face that new lanes cause congestion. What this states is that car traffic doubled over a 20 year period, and it doubled whether lane capacity increased (cities) or not (interstates).

by PeterStuer

0 subcomment

One of the reasons why this keeps getting executed is that there is a latency between added capacity and induced demand. So you can 'solve' traffic temporary just around the next election.

by Supermancho

0 subcomment

Therefore, removing lanes does not make it worse? The title doesn't pass a simple smell test. This analysis looks to try to describe no reduction in overall transit time, not what the title says.
The demand fills capacity is not a good rule of thumb either, from an economist's perspective. Shame on you. Many multi-lane highways are rather empty, why? Many roads are basically never used, why?
Lanes (transit corridors) are a river of money (funnels). When you have populations that are exchanging goods, jevon's paradox fills lanes to increase capital velocity that scales beyond the average value of infrastructure. Infrastructure cost is balanced against a perceived value, which is always skewed toward the larger (poorer) part of the population.
In this case, it's not a paradox at all that capital self-generates demand for this space. This also explains why some corridors are emptied as capital flees a locale.

by paulnpace

1 subcomments

All of the major freeway expansions I have experienced required at least two years to complete. During these periods, lanes in the construction zone were heavily constricted, resulting in all of the roads surrounding the expansion project being completely filled with stop-and-go traffic during peak hours until the projects were completed, which seems to suggest the number of lanes makes some kind of a difference in something, somehow.
The authors seem to suggest that demand for roads is infinite, as expanding roads merely increases the number of trips people choose to make, thus infinite expansion will result in infinite trips.
These analyses always appear to me as if they are without any understanding of how humans actually behave, resulting in nonsensical nonsense "laws".