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).
The study looked at what is the source of extra traffic. In most cases it was individuals living in the area doing more car trips.
Basically, an extra lane temporarily reduces congestion. The main cost of congestion to road users is time. Since now it's faster to travel, you're more likely to do an extra car trip. You continue taking extra car trips, until the cost in time is the same as pre-road expansion.
The question then is are the extra car-trips valuable.
My issue isn’t that they claim the increased congestion comes from additional personal trips. My issue is that they claim this is due to increased capacity which fundamentally seems untrue, as evidenced by the fact that traffic doubled both with and without increased road capacity.
In fairness, I have not read the 37 page paper yet. Maybe the paper makes a more compelling case than the summary article.
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.
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.
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".
> 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.
Agree. They literally claim this with “increasing lane kilometers by 1% will increase VKT by 1.03%” but subtly acknowledge that this fundamentally doesn’t make sense with the hand-wavey “any feasible increase in roadways will have no impact on congestion”. Keyword feasible.
The real law doesn’t seem to be that congestion rises to meet capacity but that no one will ever fund enough road expansion to make peak congestion low.
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).
It's actually a pretty complicated topic. CityNerd did a pretty good video on the topic here:
https://www.youtube.com/watch?v=za56H2BGamQ
The study looked at what is the source of extra traffic. In most cases it was individuals living in the area doing more car trips.
Basically, an extra lane temporarily reduces congestion. The main cost of congestion to road users is time. Since now it's faster to travel, you're more likely to do an extra car trip. You continue taking extra car trips, until the cost in time is the same as pre-road expansion.
The question then is are the extra car-trips valuable.
My issue isn’t that they claim the increased congestion comes from additional personal trips. My issue is that they claim this is due to increased capacity which fundamentally seems untrue, as evidenced by the fact that traffic doubled both with and without increased road capacity.
In fairness, I have not read the 37 page paper yet. Maybe the paper makes a more compelling case than the summary article.
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.
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.
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".
> 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.
Agree. They literally claim this with “increasing lane kilometers by 1% will increase VKT by 1.03%” but subtly acknowledge that this fundamentally doesn’t make sense with the hand-wavey “any feasible increase in roadways will have no impact on congestion”. Keyword feasible.
The real law doesn’t seem to be that congestion rises to meet capacity but that no one will ever fund enough road expansion to make peak congestion low.