I buy that traffic is bad, but it's been shown time after time that demand will grow [1] to match the new space on the highway.
That's true, but I don't know that it's such a bad thing. Taken as a given that we're paying for roads with taxes and gov't decides where to put them (I would be very open to private, toll based roads but I doubt many people would), if there is an area of high demand (e.g., heavy traffic) and they expand capacity, it makes sense that more people would now find the route attractive, until traffic again gets bad enough that people avoid it and that seems like a relatively successful operation for government. It's not a bridge to nowhere, it's a road that will actually serve unmet demand. Sure, some of that demand will be created by the road, but that's demand that is presumably moving from another area, meaning it's still opening up capacity somewhere.
First of all, I don't know that that's a sensible policy perspective, because at scale, having that much pavement to maintain will bankrupt a government or lead to it providing fewer useful services. You could say that's a slippery slope argument, but given that it's happening all around the country, I think it's hard to call that line of thinking a logical fallacy.
I don't necessarily disagree, but that's a funding issue. Ideally you would fund stuff like roads by use taxes, so funding wouldn't be an issue.
As long as the interstate system exists, we'll probably have to accept that the funding issue is a very real part of life. And if we did transition to use fee funding, we would substantially reduce the demand for these roads. Hell, even if we increased gas tax to cover ongoing costs for the infrastructure we already have (75-80 cents/mile instead of the current 18.4 cents/mile), we'd reduce demand substantially. In any case where automobile traffic was being held accountable for itself, driving would decrease. And if we're going to distort the market, I'd hope we might find a more noble pursuit than low-occupancy vehicles.
But aside from that, I would say what is a cost burden are the lightly traveled roads in lightly populated areas more so than highly trafficked interstates.
Are you referring to rural roads or residential streets when you say 'lightly traveled roads'? If it's the former, I'd tend to agree that most states are overzealous in paving and over-engineering every rut and cart-path they see. If it's the latter, I'm going to point out that interstates and residentials serve completely different purposes, the one being to move people quickly, and the other to facilitate social and economic activity. However, I'd still agree that most municipalities over-build street networks. I'd love to see land-value taxation become more widely used, which I think would lessen that problem.
I would also argue that the road is primarily not serving unmet demand. The unmet demand isn't that people aren't able to get on the road, or that they demand to be with more like-minded people hanging out in traffic. The demand is that they be able to make the drive at a speed closer to interstate speeds. That demand, in all likelihood, will not be met. In all but a few situations, the roads will fill right back up.
I would say the demand is to get from certain point A's to certain point B's along the path, and the cost if the amount of time taken. There may be, for example, 20,000 people that would like to travel a portion of that road, but the expected time is too great. You expand the supply, the expected time drops, and more travelers use the road until the expected time ends up back at equilibrium, which would presumably be slightly less congested than before, although possibly by an insignificant or even imperceptible amount. [/quote]
It's possible that you get slightly less congestion than before (as much as a 4% reduction for each 10% expansion), but it seems that even that small reduction wears off after a decade (
http://www.dot.ca.gov/newtech/researchreports/reports/2015/10-12-2015-NCST_Brief_InducedTravel_CS6_v3.pdf). Still, all you've done in the mean time is encourage more people to live in a way that is expensive, unhealthy, high-pollution, and non-resilient. And the state has incurred huge costs (and higher ongoing maintenance) to achieve those effects.
I take as a given that we will have public tax-funded roads, but I don't take as a given that we need to allow the roads' portion of tax revenue to grow unchecked. Furthermore, if this infrastructure project is undertaken by the state, what do they gain? I don't imagine CO benefits from Denver workers living in CO Springs. CO Springs is the beneficiary, but there's no way that they would pay for this on their own. Denver will pay for it right after DT finishes convincing the Mexicans to pay for his wall. I admit that, for situations where NIMBY bullshit approaches infinity, it will start to appear logical to Denver to have these people live far away. I'd argue that catering to any NIMBY stuff should be a red flag that what you're doing doesn't make much sense.
Why would the State need to benefit from it? In theory, they are taking taxpayer money and using it in ways that are beneficial to and desired by the taxpayers. I have no clue, but I would guess that if it's as congested as everyone says, this would probably be fairly beneficial compared to other road options.
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The state has some finite amount of money that they get each year from tax revenue. Putting aside questions of where the peak belongs on a Laffer curve, I think we can agree on that. They should be spending that money on projects that do the most good. So long as there is not catastrophic failure on I-25, I'm suggesting that the place where that money can do the most good is somewhere else. If you just keep the same size of I-25 and maintain it, roughly the same number of trips will continue to occur. Maybe that means fewer people commuting between CO Springs and Denver, which doesn't seem like a disaster to me. Or maybe it means that people would do more car-pooling and bus transportation, which would increase throughput with the same road. It might even encourage further mass transit development, which could be great too.