4 ms·

If you have more cars traversing the same road with the same commute time, you have increased throughput. While it might not mean much to the individual driver,

by jjk166 2y ago

If you have more cars traversing the same road with the same commute time, you have increased throughput. While it might not mean much to the individual driver, it's beneficial for the community the road serves to be able to move more people and goods around. There are also potential benefits to the individual besides reduced commute time. For many people the real pain point of congestion is travel time variability. If you expect a drive to take 30 minutes, that's not particularly onerous. But if a drive you expected to take 10 minutes winds up taking 30, that is terrible. When there is variability, either you are late to arrive or you need to add buffer to your travel time, both of which are highly undesirable. Even holding average travel time constant, if you can reduce the standard deviation through optimization, that is a huge quality of life improvement. There is also a safety concern. Congestion causes increased rates of accidents for a variety of reasons - less clearance between cars, people driving abnormally trying to make up for lost time, overflow to alternate routes, road rage, etc - which obviously is a problem for both society and the individual driver. Getting traffic to flow more smoothly, even if there were no throughput increase at all, would be a substantial benefit. Finally, induced demand is just demand that is currently unsatisfied. There are people who currently live where they don't want to, work where they don't want to, or avoid trips altogether that they want to make because of excessive congestion. Improving their quality of life while holding the quality of life of current drivers constant is a good thing.

Tiktaalik 2y ago
> If you have more cars traversing the same road with the same commute time, you have increased throughput Yes and then more cars appear. > Improving their quality of life while holding the quality of life of current drivers constant is a good thing. Sure absolutely people need to go places and we need to get them there. However we have neglected to consider the negative externalities of induced demand and the quality of life of everyone else who isn't a car driver. The geometric realities are such that induced demand can only be satisfied by growing the size of the road network. This has incredible costs and significant negative impacts on the community and environment. There are other alternatives that achieve the same goals. While there may be "efficiencies" to be found they cannot make up for the fixed dominant variables, the geometric reality of ever increasing SUV size, and fixed road sizes. As soon as any efficiencies open up free road space the amount of cars will simply increase, quickly closing that free road space again. So this doesn't mean that efficiencies can't be found, it just means that we need to understand the limits of efficiencies and we should not expect this to be a core solution to our traffic problems or as a key part of our broader transportation strategy.
- jjk166 2y ago
  > Yes and then more cars appear. This is after those cars appeared. > The geometric realities are such that induced demand can only be satisfied by growing the size of the road network. We are explicitly referring to increasing the capacity of the road network without growing its size. > s soon as any efficiencies open up free road space the amount of cars will simply increase, quickly closing that free road space again. Again, we're not looking to increase free road space, the additional cars filling that space are the benefit. There is some absolute limit on throughput where the road is completely packed full of cars all moving at maximum speed, and the only way to further increase throughput is expansion. But most road networks are no where near that limit. When you are in bumper to bumper traffic on a 60 mph highway moving at 5 mph, that road is carrying about 1/12th or 8% of its maximum capacity. That's an immense opportunity for improvement.

by jjk166 2y ago

Tiktaalik 2y ago

> If you have more cars traversing the same road with the same commute time, you have increased throughput Yes and then more cars appear. > Improving their quality of life while holding the quality of life of current drivers constant is a good thing. Sure absolutely people need to go places and we need to get them there. However we have neglected to consider the negative externalities of induced demand and the quality of life of everyone else who isn't a car driver. The geometric realities are such that induced demand can only be satisfied by growing the size of the road network. This has incredible costs and significant negative impacts on the community and environment. There are other alternatives that achieve the same goals. While there may be "efficiencies" to be found they cannot make up for the fixed dominant variables, the geometric reality of ever increasing SUV size, and fixed road sizes. As soon as any efficiencies open up free road space the amount of cars will simply increase, quickly closing that free road space again. So this doesn't mean that efficiencies can't be found, it just means that we need to understand the limits of efficiencies and we should not expect this to be a core solution to our traffic problems or as a key part of our broader transportation strategy.

jjk166 2y ago
> Yes and then more cars appear. This is after those cars appeared. > The geometric realities are such that induced demand can only be satisfied by growing the size of the road network. We are explicitly referring to increasing the capacity of the road network without growing its size. > s soon as any efficiencies open up free road space the amount of cars will simply increase, quickly closing that free road space again. Again, we're not looking to increase free road space, the additional cars filling that space are the benefit. There is some absolute limit on throughput where the road is completely packed full of cars all moving at maximum speed, and the only way to further increase throughput is expansion. But most road networks are no where near that limit. When you are in bumper to bumper traffic on a 60 mph highway moving at 5 mph, that road is carrying about 1/12th or 8% of its maximum capacity. That's an immense opportunity for improvement.