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Why isn't LA repaving streets?
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Re: Why isn't LA repaving streets?
#222Earlier quoted context omitted.
For people that don't watch the video (I don't even know if this is in the video): road wear is a function of axle weight to the fourth power . [0] That means a 6,000lb escalade creates 3x the road wear than a 4,500 wagoneer from 1990. [0]: https://en.wikipedia.org/wiki/Fourth_power_law
You are incorrectly assuming the Esclade isn't on 32+" tires with 285+mm width and the Wagoneer isn't on pizza cutters. Tire size has increased greatly on SUV and light trucks, which exerts less ground pressure. It's not realistic to do this on a heavy truck, which run 110+ PSI on heavy wall tires and why they cause the power law damage to roads.
No way does the Escalade exert less ground pressure!
Firstly, a Wagoneer is never on pizza cutters. You can't put a 4500lb car on pizza cutters even in 1990! It came with 235/75R15 tires. They are big sidewall donuts, but no pizza cutters.
The Escalade runs 285/40R24 tires, that's wide and low-profile.
Widening a tire increases ground pressure, because low-profile tires have massive amount of reinforcement to prevent that wheel from cracking. This stiffness adds to the pressure the road feels.
Tire contact patch is a function of weight and tire pressure. A 205mm width tire has the same contact patch as a 285mm tire, given same weight and pressure. The only thing that changes is the shape of the contact patch, which becomes wide and short instead of narrow and long.
The 6000lb Escalade runs its 285/40R24's on 35 psi, the Wagoneer runs its 235's at 30 psi.
So assuming even weight distribution, the contact patch per tire is 6000lbs/4/35psi=42.8in^2 inches for the Escalade, and 4500lbs/4/30psi=37.5in^2. So the contact patch is only 14% larger on the Escalade, yet it carries 33% more weight!
If you look at the road wear formula, it's entirely a function of weight. So the width of the tires only impacts surface-level abrasion. And with the power law, that's still 3.16x of Wagoneer's wear (or 216% increase).
So the wider tires do virtually nothing to protect the road from the extra 1500 lbs weight.
In fact, the dynamic load when hitting potholes is greatly exacerbated by the 285/40R24 low profile tires, because instead of of absorbing the bumps within the tire, the stiff sidewall low-profile tires absorb way less.
The spring rate of the Wagoneer tires is ~1200-1500 lbs/in, the spring rate of the Escalade tires is ~2500-3500 lbs/in, so that's a 2x stiffer tire! As a result, it transmits twice as much force when hitting the same bump.
So as a result, an Escalade accelerates road cracking considerably worse than the Wagoneer, not even in the same league.
Yes, the heavy trucks wear the road outsizely, incomparably to the SUVs we are discussing. However, we have roads that do not allow trucks (parkways) or see little heavy truck traffic.
Re: Why isn't LA repaving streets?
#223> Mozee went into detail comparing slow concrete curb accessibility work to the faster asphalt street work. Per Mozee, “there’s approximately 14 ramps in a mile.” So for “one crew to build out those 14 ramps will take approximately three months.” In contrast, he said, “a paving crew on a good day … could pave that same mile in a weekend or one week, at most.” Why don't they asphalt curb to curb for a mile and then co…
I read this section and, along with the surrounding context, it seems like the issue is less having-money-for-materials and more having-money-to-hire-enough-skilled-workers-to-work-on-multiple-ramps-in-parallel. Different budgets, perhaps?
Re: Why isn't LA repaving streets?
#224Maybe roads would last longer if we weren't all being forced to buy super heavy SUVs just so automakers can skirt emissions and fuel economy requirements. https://www.youtube.com/watch?v=JPm4de6-eTg
For people that don't watch the video (I don't even know if this is in the video): road wear is a function of axle weight to the fourth power . [0] That means a 6,000lb escalade creates 3x the road wear than a 4,500 wagoneer from 1990. [0]: https://en.wikipedia.org/wiki/Fourth_power_law
The other key takeaway from the video is that carmakers are highly incentivized to sell SUVs because they're still classified as "non-passenger work vehicles", which have looser emission requirements making them cheaper to produce.
The bug in the law really seems to be that cars that really aren't intended as work vehicles are being treated like them.
Re: Why isn't LA repaving streets?
#225Earlier quoted context omitted.
one garbage truck - 40,000 pounds wears road 2000x than escalade.
We can't do without garbage trucks though
- have less garbage
- collect garbage more frequently in smaller trucks
taiwan has very cute small garbage trucks and they have a ice-cream-truck like song signalling for people to bring whatever trashbags they have out to the truck, so you don't even have piles of garbage outside for days waiting for the weekly truck. quite nice.
Re: Why isn't LA repaving streets?
#226I have been a Strong Towns follower/member for about 6 years. I really don't think people realize the world of pain we're signing up for by not actually fixing the underlying problem of lack of density and walk-ability and their effect on the municipal budgets of American cities. https://en.wikipedia.org/wiki/Strong_Towns I know municipal finance is about as exciting socks for Christmas, but if the Strong Towns thesi…
this is coming from someone who lives in san francisco like you and has a 2 kid, 4 adult family with no car. it's been like 80 years of USA = cars. people seem to really like SFH + cars, they vote for it, they pay for it, and seem to accept even longer commutes than ever. consider why. it's not so simple.
> Strong Towns thesis is correct... slow moving crisis... The idea that LA literally can't afford to bring it's sidewalks up to ADA code is insane
see, this tells me you're not getting it at all. it is an insult to process, yes. But there's no crisis. Strong Towns is kind of obviously wrong.
Re: Why isn't LA repaving streets?
#227Earlier quoted context omitted.
I suspect you don't understand how serious the problem is. The problem isn't "we need to add bike lanes." The problem is that the streets have to be repaved anyway and if the city can't afford to simply bring them up to code in the short run , then they can't afford to keep repaving them at all in the long run. The sidewalks are going to have to be completely replaced eventually... not just the sections that need ram…
"the code" is the issue. This isn't building code like protecting earthquakes, electrical, fire safety. When people hear "the code" -- they think critical safety measures. Activists came up with a doorjamb law to require bike lanes, ADA and road diets on every block that receives repair. That's just not practical in LA. You can't punish drivers into riding a bike to work. this is coming from someone who biked and bus…
As someone who has biked and rode trains to work for the past 30 years and continues to do so, I think requiring bike lanes whenever streets are repaved is a pretty awesome idea. ADA ramps are pretty great too, they are not just for disabled people, though the ADA lawsuit regime where private companies get sued needs to stop.
Yes I understand there is a funding issue, it needs to be solved by making the design and approval process more flexible and efficient, not by perpetuating the insane car-only design that kills pedestrians and cyclists.
Re: Why isn't LA repaving streets?
#228Earlier quoted context omitted.
When I say "trivially fix" I mean that, if the City/State wanted to fix the problem, they could. >Re-zoning only works if there are developers who want to redevelop the land. Developers very obviously want to redevelop the vast majority of LA. The marginal cost of a housing unit is vastly higher than the cost of building that unit. To raise long-term tax revenues, LA could not just legalize redevelopment. They could…
Every time I look at a city/county budget, the schools absolutely dwarf everything else (it's not quick to disentangle different levels of government, but roughly speaking, it seems like schools are usually roughly the same cost as all other services combined where I've looked), which makes it hard for me to take seriously the idea that it's infrastructure like roads and sewage specifically leading to unsustainable b…
Take a look at LA’s budget then, it’s literally all police and police liability payouts which are already hundreds of millions of dollars over the budget for them.
Re: Why isn't LA repaving streets?
#229I have been a Strong Towns follower/member for about 6 years. I really don't think people realize the world of pain we're signing up for by not actually fixing the underlying problem of lack of density and walk-ability and their effect on the municipal budgets of American cities. https://en.wikipedia.org/wiki/Strong_Towns I know municipal finance is about as exciting socks for Christmas, but if the Strong Towns thesi…
> lack of density One interesting question: what is "density"? Is it number of people per road-mile? Number of households? Structures? Sales tax revenue? Property tax revenue? Property value per road mile? LA has somewhat insane property values right now, and by the metric of millions of dollars of residential value per road-mile, I think one might imagine the density to be sufficient to afford decent streets. Of cou…
Tax revenue per area is generally a good metric in terms of the sustainability of a municipal budget.
Very few suburbs in the world have enough people density to clear that bar, no matter how much they tax them. More people density lets you clear the bar so much easier even when the incomes are drastically lower.
Re: Why isn't LA repaving streets?
#230Earlier quoted context omitted.
I think Chuck Marone and his group make good points but their admonition by ASCE is also deserved. He really went too far with disparaging the profession because of differences in purely value judgments. Furthermore, the type of infrastructure you get is a political decision. Civil engineers don’t tell your mayor or your highway commission what to build, their only job is to figure out how it can be built. The “what”…
The engineers are a big part of the problem and drive regulations that featherbed themselves. I got into a fight with my city over nonexistent crosswalks (the adhesive line strips wore off) near my home in an area where drivers have a hard time realizing where pedestrians cross due to a unique road setup. You can’t just paint lines. The project ended up costing about $1.2M and required a traffic study, some stupid AD…
I love a good rant, but you just have no idea what you’re talking about. First, real engineers (the kind with, education and experience requirements and personal liability for their work) have labor markups that are maybe 2 to 3 times raw rate. I don’t know if 6X margins are normal for people who collect a check to “maintain” a finished product. Second, any civil engineer will tell you that complete streets compliance for federal funding is a waste of everyone’s time. Engineers didn’t come up with that, congressmen elected by people like you came up with that. Third, the only reason they did all of that study is because the people you voted for wanted to use money that was tax farmed from me instead of your city funds. They could have just sent out a road crew. You could also cut the check yourself. Finally marked crosswalks alter pedestrian behavior, but not driver behavior. Marking crosswalks where there is high traffic and no controls like a signal with a dedicated pedestrian phase are actually more dangerous than no markings at all. I don’t expect you to know that, but that’s why you should hire people like me and not try to do this yourself.