Fly on A Windshield

[Overmod]

Erik_Mag

I suspect that road damage has a lot of threshold effects such as a concrete road with a bit of the underlying roadbed eroded away. The concrete could be strong enough to allow a large number of autos to cross over, but then could break with the first truck. The threshold in this case would depend on the strength and thickness of the concrete, the size of erosion, characteristics of the roadbed, etc.

Some of the effects are highly nonlinear, both in terms of momentum and contact pressure.  Not much modeling is required to produce meaningful models in a number of respects demonstrable in regular experience.

The impact of surface abrasion, in part due to high tire pressure and poor suspension compliance, can be graphically demonstrated in a couple of European 'guided rubber-tired tram' systems, a couple of which we discussed in this respect a few months ago.  This need not be propagating 'point defects' in pavement leading to potholing, or progressive distortion of asphalt structure; a particular example was the original construction of I-20 east from Shreveport, built as 20' slabs with control joints between them but tied longitudinally by tendons. Shock at the joints over time resulted in these slabs rocking up at the 'front' progressively so that traversing the pavement in any lane was climbing a number of short relatively sharp grades followed by rebound weight transfer onto the back.  It was impossible to take this at any particular speed in anything but a softly-sprung vehicle with relatively long suspension travel; there was no economical 'fix' (like mud-jacking to level) other than physically breaing up the slabs, changing a significant depth of subgrade, and re-laying the whole shebang.  This has been done a number of other places, notably I-40 in east Arkansas, and is notable because vehicles even up to the size of class 4 trucks don't produce the impact necessary to start the slab rotation; I consider it comparable to the types of rail and roadbed damage with HAL above 315K where things like cold flow in the railhead steel become nonlinear beyond the elastic limit.  

[JPS1]

Erik_Mag

Thanks for your perspectives.  Very helpful!

[Erik_Mag]

JPS1

To know how much damage a truck does to the roadways, one would have to take a sample from every type of roadway surface in every geographical region of the country under various weather conditions.  It would also be necessary to normalize the data for the different classes of trucks and the varying loads that they carry.  A Frito-Lay truck hauling potato and corn chips, even when fully loaded, would have a different impact than a gravel truck.  It would be a daunting task.

I suspect most of the studies have relied on computer modeling to come up with their findings.  One should be cautious of computer models, although I have used them for a long time, because of the difficultly in loading them with precise, verifiable data.

Especially with anything to do with extremely non-linear behavior. I suspect that road damage has a lot of threshold effects such as a concrete road with a bit of the underlying roadbed eroded away. The concrete could be strong enough to allow a large number of autos to cross over, but then could break with the first truck. The threshold in this case would depend on the strength and thickness of the concrete, the size of erosion, characteristics of the roadbed, etc.

In March, as COVID-19 became a problem in the central Texas community where I live, the University of Texas used its modeling expertise to convince the county judge that 17.8 percent of the population would come down with COVID-19.  To date the percentage of people contracting the disease is 8 tenths of 1%.  And the curve in the county is bending downward.

The impression I have is that the process of how COVID-19 infects people is not known well enough to create a reasonable model from first principles. A couple of big unknowns are how many infections are asymptomatic (or nearly so) and how many people have some immunity based on prior exposure to other coronaviruses.

It was interesting to see the updating of the IHME model, seeing it was so-so in modeling Pacific coast states, grossly underestimating NYC and overestimating places like Wyoming. Best description of the model was "a curve fitting exercize".

 

[JPS1]

Commercial trucks, airlines, barges, etc. have the advantage of sharing common infrastructure.  They share the front and ongoing costs with non-commercials users.  As noted, however, the railroads have to front the cost of their infrastructure and maintain it.

 

The question of whether the commercial users of the common facilities pay their fair share will be argued until the cows come home.  The issue will never be resolved satisfactorily for some if not all of the commercial users of the common facilities.

 

One way around the dilemma would be to have an independent, third part operator own the railroad infrastructure, and rent space on it to any operator that could meet the operating, safety, and health standards.   This is how the electric transmission system in Texas works.  But I don’t think the railroads would ever go for it.

[JPS1]

The most efficient and effective way to achieve a balanced transport system would be for everyone to see the fully allocated cost of their mode of transportation at the price point, i.e. ticket, pump, etc., and pay it.

 

Unfortunately, given the politics surrounding transportation, it will never happen.  And so those with the loudest voices and deepest pockets will win favor for their choice at the expense of others that will have to make up the difference.

 

The subsidies associated with U.S. transport are mind boggling.  Attempting to determine who gets what and when would challenge the best of forensic accountants and/or investigators. 

[Bruce D Gillings]

My apologies for not being clearer: over the years my comments regarding trucks/railroads have referred to line-haul intermodal vs. OTR.

 

I believe that rail/truck line haul/dray partnership is the most viable method of volume hauls where lane density justifies it. Not current rail lane density, but rather OTR lane density. Delivery trucks within several hundred miles will normally be the most cost-effective.  Longer, combine it with rail service WHEN it can meet supply chain needs (it usually cannot these days). I am not suggesting that rail replace the truck from a Walmart DC to a store, or an Amazon fulfillment center to your home, or a Sysco Ops Center to a restaurant. But far more market pairs than railroads now serve can support intermodal – quality intermodal (almost an oxymoron) – in trains or blocks.

 

I am on the development/design/build side of industrial facilities; have been since the 1980s. Of the hundreds over the years, only two of them are regular rail users (that is, carload). With those two exceptions, every other facility I’ve done (and am still doing) is 100% trucking. That includes intermodal.  I can’t profess to know all the ins and outs of operations. But I do know trucking is the lifeblood of non-bulk operations. I would never suggest that when we build a large DC in Southern CA’s Inland Empire that a train replace a ready-mix concrete truck or flatbead hauling steel from a fabricator in Central CA than a train replace a drayage truck from the ports to the finished DC.

 

Cost-effectiveness in today’s world: the lowest RATE being charged (when it is rail) is not necessarily the lowest COST in the supply chain. Using rail, whether it is carload or intermodal, may have a lower rate than OTR, but it often has a higher cost to the supply chain providers, whether direct transportation cost or the value loss from the inability to reliably meet customer demands. That is almost entirely the result of the culture of railroad management that has existing for decades, and now becomes exacerbated by the PSR race to the bottom that is unresponsive and unaware of how supply chains are changing. Rail relevancy is disappearing. Loose-car railroading is nearing the point of unsustainability of the needed siding/branch/yard infrastructure. If railroads disappeared entirely tomorrow, we would be fine, although a bit bruised. If trucking disappeared our consumer economy as we know it would collapse.

 

There are many studies with a large range of road wear impacts from trucking (both OTR and delivery/drayage). Years ago I responded to a post referencing a handful of them with quite a wide range; you can search for that. Most focus on maintenance impacts.  Some reports suggest trucking rates would  increase 5% if they paid true maintenance costs; some say 10%; some say 25%. Of course those are rounded, simplified numbers.  Some reports don’t look at original engineering/construction costs on roadway sections and bridges. That is huge. More important, they don’t identify that, by having road infrastructure be a government responsibility, the cost of RISK to users – trucks – does not exist.

 

The per-lane-per-mile front-in cost of the infrastructure of I-84 across Montana is comparable to the cost of I-15 between Barstow and Provo: the truck traffic differences are huge. The trucker has no risk in that front-in cost, and does not need to borrow anything to pay it back. (of course they pay through their taxes, disproportionately low), They only pay when used, even though taxpayers/government built the world-class infrastructure. No risk. Railroads, by contrast, not only have to pay the direct risk cost of capital, but if traffic patterns change, they continue paying for those front-in costs. Huge risk. The decision to invest becomes far more consequential to them than OTR trucking. Rail is dealing with more of a “pure capitalism”; trucking is not. Railroads cannot compete from an investment standpoint. I’m not saying we should not invest in roads: I’m saying that we should completely change how we treat infrastructure investment for all modes. I think that is where you would find a much more robust rail freight network. Mostly intermodal (you know, where the trucks handle the end moves….). 

 

The only way I can see railroad management culture changing is if the investment environment ever changes.  Which I seriously doubt it ever will.

[blue streak 1]

Well our I-85 south of  Atlanta has evidence.  Near the weigh station the outside lanes are so bad tht all drivers in the know always drive in the left lane.  GDOT is trying to repair but already one repair is failing.  The right lane overall is a killer to cars suspension.

Last trip to NYC rode on several of the no truck parkways. Original pavement is still good 60 years later.

[JPS1]

Bruce D Gillings

JPS1 said:

The truckers don’t pay for the roadways.  The people who buy the goods shipped on the trucks pay for them.  The cost of transportation is baked into the price of the goods people buy nearly every day.  Increasing the cost truckers pay will ultimately be paid by the consumers. 

The point is pretty simple: when freight moves by rail, you, the consumer, have the opportunity to pay less overall. 

Not necessarily.  I have a difficult time believing that shipping goods to a Walmart or my HEB by rail would be more cost effective than moving it by truck. 

Some of the stuff at Walmart comes from overseas, and it is shipped in containers by rail to distribution centers.  But it is trucks that make it economical to get it to the store.  And this would be true even if the fuel tax paid by trucks was doubled.  

A 2000 study released by DOT, based on 1998 data, found that five axle trucks paid approximately 60 percent of the cost to build and maintain the highways they use.  But other trucks paid their fair share, with some trucks paying more than their fair share.  The results are dated, but they highlight an important point.  Not all trucks have the same impact on the roadways that they use.

To know how much damage a truck does to the roadways, one would have to take a sample from every type of roadway surface in every geographical region of the country under various weather conditions.  It would also be necessary to normalize the data for the different classes of trucks and the varying loads that they carry.  A Frito-Lay truck hauling potato and corn chips, even when fully loaded, would have a different impact than a gravel truck.  It would be a daunting task.

I suspect most of the studies have relied on computer modeling to come up with their findings.  One should be cautious of computer models, although I have used them for a long time, because of the difficultly in loading them with precise, verifiable data.

In March, as COVID-19 became a problem in the central Texas community where I live, the University of Texas used its modeling expertise to convince the county judge that 17.8 percent of the population would come down with COVID-19.  To date the percentage of people contracting the disease is 8 tenths of 1%.  And the curve in the county is bending downward.

[Bruce D Gillings]

JPS1 said:

The truckers don’t pay for the roadways.  The people who buy the goods shipped on the trucks pay for them.  The cost of transportation is baked into the price of the goods people buy nearly every day.  Increasing the cost truckers pay will ultimately be paid by the consumers. 

And the consumers pay even if the truckers don't pay.  You either pay indirect hidden costs - that is, you pay for it yourself but have no idea you are because your little Prius is paying disproportionately high - or you pay through the increased costs of the goods you purchase.  Either way, you pay.  It doesn't appear out of thin air, or disappear into thin air.  The point is pretty simple: when freight moves by rail, you, the consumer, have the opportunity to pay less overall. Because the wear and tear caused by trucks on the road is reduced when a more cost-effective way of competeing exists. 

 

Unfortunately, when that cost is hidden, and YOU are paying through your fuel costs and road use fees disproportionately, you think trucks are a bargain. Target, Walmart, Amazon, Home Depot, whoever, gets to pay less for trucking than they really should. And all the while, OTR trucking looks better by comparison than rail, either intermodal or carload. 

 

We will never get trucking to pay its true costs of road impact wear and tear. Our current political environment (likely to exist many, many years after most of us are gone) will not allow it. The solution? Give freight railroads 100% or 90% or 80% tax credits for anything related to infrastructure improvements to mitigate to a reasonable extent the hidden subsidy that imbalanced impact cost allocation creates. Make investing in additional main tracks, sidings, terminals, streamlining of 19th Century alignments far less risky, and far less costly, for railroads. Incentivize freight infrastructure investment to the point that management is not at risk of being booted out for growing the franchise. 

No matter what is done, the consumer always pays for it. They pay the least when transportation is provided in the most cost-effective way. And that, when looking at every aspect of costs, is rail - with a very big caveat.  That being: rail mangement and operational institutional knowledge is falling apart.  PSR - which is anything BUT precision and scheduled, is taking railroading down a drain counter to what the world of logistics wants. Railroad management is blinded by their own costs, and is oblivious to the true costs of theri collapsing service metrics on supply chains. And thus the race to lower costs is a race to the bottom of transporation relevancy.  Lower costs in railroading through lower rates often mean increased costs to supply chains who use rail.  And so the it goes.

 

Unfortunately, the methodology used to identify that, by hiding true costs, skews the game against rail. Something has to change, or we'll be left with a handful of bulk routes, commuter rail, and a handful of Amtrak "corridors". 

 

Complaining about how bad the roads are now is pointless.  The public is too busy being entertained by "America's Got Talent" or whatever news outlet appeals to their notions of reality to give a damn about truck damage to roads. At some point they'll just keep paying more taxes, one way or another. Change how railroad investment in infrastructure is treated or get your pictures now of freight trains: they're a dying breed.  

 

[alphas]

Last I heard from individuals who worked in the PA Transportation Institute about 4-5 years ago, modern trucks caused anywhere from 6 to 10 times the damages vs. what they were paying in fuel taxes. 

The best solution they could give me back then was a combination of increasing diesel fuel taxes, get rid of the requirements that Davis-Bacon and other prevailing wage labor laws impose including those requiring only union labor, reform all the endless rules that delay construction for years, modernize the standars governing how much concrete & base are required, stop contracting with companies that have mob ties, and rquire a work performance bond of enough magnatude and length that you don't have to worry about the roads rapidly deteriorating.

The only one of those that has started to happen has been some reduction of federal rules that happened in the last several years under the current administration. 

Road contractor associations actively lobby against increasing initial standards and accountablity.      They tend to be based in a geographical area and once roads, etc. are built they want enough continous repairwork coming their way until there's once again major construction in their area.   

Unions will fight any changes to the current system and continue to try and get it mandated that all Federal & State highway projects have to be union labor only.     Obama mandaed unions for his "shovel ready" program which was one of the reasons it never got close to its promises.    Since the majority of the states actually have very few union contractors, that and his failure to reduce the delays for construction projects were major reasons for the program basically being a dud.   Biden is calling for another "shovel ready" program if elected but if he runs it like Obama did it will most likely have similar results.

Whatever the answers are, the customers will be paying more for the products shipped.      The only exception to that would be products produced locally where transortation costs aren't a significant factor.

[JPS1]

As per Status of the Federal Highway Trust Fund, Table FE210, in 2016 – latest reported numbers - trucks generated directly or indirectly 37.7 percent of the HTF revenues. 

 

As per Table I-35, Vehicle Miles, U.S. National Transportation Statistics, in FY17 single-unit 2-axle 6-tire or more trucks and combination trucks – five axles or more – accounted for 9.2 percent of vehicle miles traveled. 

 

Light duty vehicle, long-wheel based vehicles, which includes some commercial delivery vehicles, as well as Billy Bob’s pick-up, accounted for 20.4 percent of the vehicle miles traveled. 

 

Passenger cars, which include SUVs, accounted for 69.1 percent of the miles.  The remainder were accounted for by buses and motorcycles. 

 

So, trucks of all classes accounted for 9.2 percent of the vehicle miles traveled in 2017, but generated approximately 38 percent of HTF revenues before transfers and adjustments. 

 

Most trucking firms also pay federal and state income taxes.  A portion of them find their way into the transfers from the General Fund(s) to the HTF.  In 2016 the federal transfer to HTF was $50.9 billion, but this amount was for a five-year period beginning in 2017. 

 

The issue is not whether truckers pay more for the roadways they use than other users - they do as shown above; the issue is whether they pay an appropriate  proportional share – higher build standards and more maintenance - to build and maintain the roadways that they use.

 

The truckers don’t pay for the roadways.  The people who buy the goods shipped on the trucks pay for them.  The cost of transportation is baked into the price of the goods people buy nearly every day.  Increasing the cost truckers pay will ultimately be paid by the consumers. 

[NorthWest]

https://freight.amazon.com/blog/article/blog-full-truck

Amazon is expanding its role as a freight broker.

Another step towards Freight Mobility as a Service or the Uberization of trucking.

This will be interesting to follow going forward.

[daveklepper]

SALfan and RRnut, Hooray for you.  Write your Congressment and Senators!

[rrnut282]

Trucks pay less in highway (fuel and toll) taxes than the damage they cause now.  Why would anyone with a brain permit heavier trucks that can do more damage per trip without "catching them up" with respect to paying for the damage caused?

[Overmod]

I was referring strictly to il Commendatore as an engineer, and the early work in the '40s, for example the design of some of the early V12s.  Ferrari as a 'brand' is, as you say, the beneficiary of certain other Euro talents... just as, arguably, the vicissitudes of the resurrected Bugatti company are in less satisfactory ways.

[BaltACD]

Overmod

Just remember the difference between European heaven and European hell...

... although there are a couple of comparatively recent engineers of Italian extraction who were anything but incompetent, Ferrari and Bugatti being two fairly familiar ones.  I would also include Bartini in there although some may think him too reminiscent of Victor Pirolo.

Ferrari in the 21st Century of racing has only shined when its leaders were a Britian, a Frenchman and a German - Ross Brawn, J Todt and Michael Schumacher - other than the times those three were 'in the drivers seat' Ferrari has acted as an Italian fire drill.

[Overmod]

Just remember the difference between European heaven and European hell...

... although there are a couple of comparatively recent engineers of Italian extraction who were anything but incompetent, Ferrari and Bugatti being two fairly familiar ones.  I would also include Bartini in there although some may think him too reminiscent of Victor Pirolo.  I don't think Colani is in that league...

[Flintlock76]

Psychot

I love Italy and its people and that idea seems logical... but I can't help thinking that we're in deep trouble if we emulate Italy on anything related to infrastructure or finances...

Uh, yeah, I'm half-Italian myself and I have to agree with you, considering the bridge collapses they've had in the past few years.  They're sure not building them like the Romans used to.

[Psychot]

tree68

 

 

Shadow the Cats owner

Instead of the cheapest bid wins how about requiring these freaking contractors stand behind their work for at least 10 years.  

 

 

Years ago I read that the Italians dealt with that issue by throwing out the high bid (clearly looking for a gravy train) and the low bid (clearly gonna cheap it out), averaging the rest and selecting the bid closest to that average.

Sounds reasonable to me...

 

 

I love Italy and its people and that idea seems logical... but I can't help thinking that we're in deep trouble if we emulate Italy on anything related to infrastructure or finances...

[Psychot]

Flintlock76

 

 

Psychot

I've driven most of the German autobahn system at one time or another over the past couple of decades, and I can tell you that parts of the system are in pretty rough shape. I'm not sure that's entirely attributable to trucks, but I would imagine that plays a role.

 

 

Dang!  If that's the case the Germans sure ain't makin' concrete like they used to!  It took direct gunfire from eight and fourteen inch naval guns to knock out some of those Normandy bunkers, and the flak towers built in some German cities during WW2 were so tough they never tried to demolish them in the post-war era, it was easier just to leave them standing. 

The Luftministerium  building in Berlin was so strong Allied bombs bounced off it!  It's still in use today by the German government, although not as an air ministry.

And speaking of flies hovering over freeways, you know how you spot a happy motorcyclist?

He's the one with bugs in his teeth!

 

Yeah, when I was stationed in Berlin with the USAF in the late 80's, my barracks and support facilities were at Tempelhof Central Airport. That structure is so thick and well-constructed that I can't imagine trying to take it down. They truly built things differently back in those days.

[SD70Dude]

Euclid

Crumbling roads are a handy pretext to raise taxes.  So there is no incentive to make them last long.  Nothing speaks to a driver like a pothole. 

And yet the U.S. federal gas tax has not been raised since the 1990s.  Not even to account for inflation, which of course in reality has resulted in a loss of revenue for the highway trust fund.

[blue streak 1]

All Concrete is not the same.  Type of cement and how much moisture removed out of cement in the kiln.  Storage of cement to prevent moisture getting into cement.  Aggretage needs a certain strength.  Granite usually the best but there are many grades of granite.  Limestone is mostly now a no - no. Then the smaller the size of the agreate the more cement for a given strength.  The less the amont of water the better.

Then you have subgrade to worry about.  Compaction of the subgrade important and prevention of future voids under the concrete very important as concrete not good in tension but great in compression. 

A new way to mitigate the problem of future voids is to put down a layer of asphalt before pouring concrete.  Asphalt is classified as a super cooled liquid that will slowly flow into any subgrade voids  That keeps pavement above lying on a more even subgrade.  Newark airport (EWR) laid asphalt under concrete for a runway extension.  No breakup of the extensions last time there.  They have slowly replaced original runway by matching with the extensions as an old section goes bad.  Note:  EWR is built on a previous sandy type soil.  Note depth of concrete also important but needs type of concrete to be determined.

Even construction engineers make mistakes.  The flyover TriRail bridge over the New River was discovered by CSX to have too much fly ash in the concrete. Delayed finish of bridge for over a year This poster is no concrete engineer.  Need to ask Mudchicken about his many screw ups he observed.  Here is a link for all you want to know with a mind boggling overload about concrete,

https://www.aboutcivil.org/types-of-concrete.html#:~:text=Types%20of%20Concrete%20and%20their%20Characteristics%201%20High,Pervious%20concrete.%20...%207%20Roller%20compacted%20concrete.%20

[tree68]

Shadow the Cats owner

Instead of the cheapest bid wins how about requiring these freaking contractors stand behind their work for at least 10 years.  

Years ago I read that the Italians dealt with that issue by throwing out the high bid (clearly looking for a gravy train) and the low bid (clearly gonna cheap it out), averaging the rest and selecting the bid closest to that average.

Sounds reasonable to me...

 

[Shadow the Cats owner]

The cost of road pavement such as asphalt cement aka liquid asphalt portland cement labor and other items used in highway construction has more than doubled with asphalt going up almost 10Xs since the last time the Federal Government raised the highway fuel tax in the 90's.  Back then you could get liquid asphalt for about 29 dollars a ton now it is going for about 245 dollars a ton for the liquid portion of it.  Labor has gone up also in 1992 a truck hauling asphalt was paid around 70 bucks an hour for the truck total.  Now they are getting almost 300 bucks an hour for the truck total.  Let alone the labor of the contractor worker.  Yet the fuel taxes have not increased at all at the Federal Level.  Yes some states have increased it to try and do something about the shortage for highway repairs but at the Federal Level nothing ever gets done.  Instead they are more worried about I swear it seems wheter or not at least right now if removing the Founding Fathers is needed from our history.  My boss has flat out said he has NO problem seeing the Federal Fuel tax raised by at least 30 cents a gallon as long as all money collected from it is USED ONLY FOR HIGHWAY construction along with a redo of how highway construction contracts are issued.  Instead of the cheapest bid wins how about requiring these freaking contractors stand behind their work for at least 10 years.  

[SALfan]

Some entity (I think the University of MD, but it's been too many years to be sure) did a study years ago that said one semi did as much damage to a road as 6000 automobiles.  Find a road with a lot of truck traffic, and unless it was recently repaved it will be VERY rough.  And they want to raise truck weight limits?  Not if I have anything to say about it.

[Flintlock76]

Psychot

I've driven most of the German autobahn system at one time or another over the past couple of decades, and I can tell you that parts of the system are in pretty rough shape. I'm not sure that's entirely attributable to trucks, but I would imagine that plays a role.

Dang!  If that's the case the Germans sure ain't makin' concrete like they used to!  It took direct gunfire from eight and fourteen inch naval guns to knock out some of those Normandy bunkers, and the flak towers built in some German cities during WW2 were so tough they never tried to demolish them in the post-war era, it was easier just to leave them standing. 

The Luftministerium  building in Berlin was so strong Allied bombs bounced off it!  It's still in use today by the German government, although not as an air ministry.

And speaking of flies hovering over freeways, you know how you spot a happy motorcyclist?

He's the one with bugs in his teeth!

[Psychot]

Flintlock76

 

 

zugmann

Yeah, let's increase truck weight - since our roads are in such GREEEEEAAAT shape.

 

 

I hope you get paid for these posts.  Otherwise, I have zero clue why you're here. 

 

 

 

 

I don't know about the rest of Europe, but the concrete on Germany's Autobahn is three feet thick!  It can take any pounding you throw at it.

How many American highways are three feet thick?  Not too many I'd guess.

 

The roadbed and surface combined on present-day autobahns is 27 inches thick.

I've driven most of the German autobahn system at one time or another over the past couple of decades, and I can tell you that parts of the system are in pretty rough shape. I'm not sure that's entirely attributable to trucks, but I would imagine that plays a role.

[Flintlock76]

BaltACD

Lowest bidders don't build with 3 foot thick concrete.

Therein lies the problem.  If you're going to allow mega-trucks on your highways you'd better have mega-roadbeds to match.

Lowest bidders?  Tell me about it!  When we moved here in 1987 there was a stretch of highway recently built that was a magnificent road, but ten years later it looked like it had been worked over by heavy artillery!  

[Euclid]

Crumbling roads are a handy pretext to raise taxes.  So there is no incentive to make them last long.  Nothing speaks to a driver like a pothole.