bid_time wrote:
valhalla360 wrote:
bid_time wrote:
Increasing the load by 12.5% increases the road wear by 42% - BULL!!
THERE IS NO STATISTIC TO BACK UP THAT HYPOTHESIS.
"Some Road Planners say the toll is higher". Who are these road planners? The NCAT has a test track in Alabama. These use real world pavements and test them with real world trucks. They use real world tests to ASTM standards, to compute real live data - NOT "some road planners" talking out of his butt with nothing but hot air to back it up.
Not sure about the exact percentages but they look right.
Back in school in our pavement design courses, we reviewed studies done back in the 50's. The govt built test tracks and paid drivers to drive them 24/7 with trucks of various loads.
The common number thrown out is that a fully loaded interstate semi does 10,000 times the damage of a typical passenger car and the relationship increases with the square of the weight, so a truck that is twice the legal limit (Michigan allows that as an example) won't do 20,000 times the damage of a typical car but 40,000 times the damage.
When we design interstate pavements, we don't even consider passenger cars. They are such a tiny percentage of the calculation that they don't matter.
If you want to see an example, find a weigh station (it must be in regular use and that's often not true as cutbacks leave many closed for long periods) and watch the pavement was you go by it. What you often see is a pavement that was in bad shape suddently get visibly better as soon as you pass the exit ramp and as soon as you pass the entrance ramp it goes back to being bad.
Now to take a step back, that doesn't mean the average semi should pay 10,000 times the taxes. Roads need to be repaired and replaced due to two distinct failure mechanisms:
- Heavy trucks beating the snot out of them
- Simple age: If you prohibit any vehilce larger than a smart car and give it 20-30yrs, you will find the pavement starts to show failures. They will be somewhat different in nature but failures none the less (the exact type depends on the pavement type and the environment).
On top of that, the average freeway can accomodate all the trucks in a single lane per direction, easily. It's the multitude of passenger vehilces that create the need for 2,3,4 or more lanes in each direction. If you built and maintained a truck only roadway, you could cut the costs drastically.
Taxes related to trucking should go up from where they are now but passenger vehicles should still make up the bulk.
As far as the idea that consumers will pay more for goods...they already are, it's just that that you will see the direct cost rather than having it hidden in taxes.
Every thing you say is technically correct. However, you did not take into account the design load of the pavement. Now,you have to decide what your definition of the term "damage" is. Now a 1 lb load on a pavement with designed for a 80,000 lb load will have nill effect on the pavement, you can increase that 1 lb load by a thousand, and it still will have nill effect. Until you start talking about design load vs. actual load there is no correlation in load vs. damage.
So I will say it again. On second thought, forget it, this is a nonsense discussion; and was all started by some un-identified "road planner, with no background, no data, and no basis in fact. I'm done.
Everything I said is both technically correct and accounted for in design.
What you are trying to describe with your 1# to 1001# load analogy is called fatigue damage. It is at the heart of pavement design. As I said, when designing pavement, we don't even consider passenger cars. They simply don't do any significant structural damage. The cost related to passenger cars is mostly in the additional miles of pavement required along with the base costs for Right of Way, traffic signals and other ancilliary work needed for the road system.
To make an analogy: You need to determine the size of a tank of water. You have 10,000 individuals who will come by and dip a single cup of water out of it a day and one guy who will drop in a 1000gph pump in the tank and run it 24/7. Yes, the individuals with thier cups will have an effect (625 gallons per day). The guy with the pump will pull 24,000 gallons per day. Assuming you need a tank large enough for a weeks usage, and tanks come in increments of 50,000 gallons, it makes no difference if you ignore the individuals with thier cups. Where the individuals come into play: Instead of a simple ladder to get occasional access to the pump, you need to build a stairway to get to the tank, you need sidewalks to get from the parking facilities, you need parking facilities, you probably need to put in restrooms, etc... (ie: pavement is only one component)
I was trying to simplify it for this discussion but we don't actualy use the number of trucks. We use ESALs (Equivilent Single Axel Loads) to determine the appropriate pavement. ESALs take into account the various types of trucks from Single Units (typical Fed Ex) up to the heaviest trucks and converts them into a combined number that can be used for pavement design. Again, we don't bother with passenger cars because they are such a small fraction of the damage.
As far as the trucks paying 35 times the taxes & fees, well if they are doing 1000 times the damage per mile and they travel say 5 times the typical car, that's 5000 times the damage. Sounds like they aren't paying enough.
To your final point about it being an irrelevant discussion: Over the next 10-15 years, expect much of the interstate system to change over and local roads are likely to follow soon after. This was not a single isolated individual discussing the subject. Every state I'm aware of is looking into this. It may come out under a different format but you can expect pay per mile driven to become the norm.
