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Jul 21, 2006 (11:05 am)
Here is where the physics gets interesting.
when a weight is placed on a given surface, the force applied to that surface begins to spread out and downward through that surface at an angle corresponding to that material's natural angle of repose.
for ease of calculation, let us assume that the force would spread out and downward through A 1 foot thick non reinforced concrete surface at a 45 degree angle. Next we set a 1000LB weight on that concrete surface that has a 12 inch by 12 inch contact patch. As the weight from that object is transferred outward and downward through that 1 foot thick concrete, it is spread out to cover an area of approximately 3 feet by 3 feet. The pressure imposed on the road underlayment under that concrete is about .77 pounds per square inch.
If we put a 4000LB weight with a contact patch measuring 24" by 24", the weight transferred through that 1 foot thick concrete road surface, to the ground beneath, would be 1.73 pounds per square inch.
This calculation shows how 2 different weights that exert the exact same PSI at their contact patch, can exert radically different PSIs to the road underlayment.
#313 of 331 Re: [coalburner]
Jul 21, 2006 (11:18 am)
I guess a point where we can agree is making the cost per mile based on weight of the vehicle. If it is made strictly by weight we will be paying $100 a pound to have our tomatoes delivered to the store. I think the direction Oregon is going is more in line with the HOV lanes in CA. They charge a price based on traffic volume. The busier the highway the higher per mile charge. I think that is how they do Fastrack highways around here. That becomes even more challenging for the folks keeping tabs. I can see changes coming though.
#314 of 331 Re: [coalburner]
Jul 21, 2006 (11:22 am)
I could be wrong on this but I'd always heard that the majority of road damage is cause by weather and the elements. That portion has to be spread evenly amongst all drivers. So even if heavier vehicles caused twice the damage of lighter vehicles it still shouldn't equate to them having to pay twice as much for road maintenance.
#315 of 331 Re: [coalburner]
Jul 25, 2006 (10:17 am)
""Pavement damage increases exponentially with the weight of a truck. For example, one 80,000-pound five-axle truck does the same road damage as 9,600 automobiles"
Yes. But I think you draw the wrong conclusions.
Let's assume the "9,600 automobiles" was based on an average weight of 3000lb vehicles. And let's further assume that a vehicle twice as heavy (6000 lb SUV) does 4x the damage of the 3000 lb car. So the damage done by a single 80,000 lb truck would be equivalent to the damage done by 2400 vehicles (9600/4) with an average vehicle weight of 6000 lbs.
I don't know about where you live, but in my neck of the woods the ratio between semis to other vehicles is a LOT higher than 1 semi per 2400 vehicles (let alone 1 semi per 9600 vehicles). It's probably closer to 1 semi per 50 vehicles. So, even if the entire passenger car fleet was composed of 6000 lb vehicles, the vast share of the deterioration of the roads would still be due to SEMIS, and not cars/SUVs.
BTW - semi owners DO pay a much higher vehicle registration fee; this is to help offset the greater damage they inflict to the roads.
Remember, the gas taxes are not JUST for road maintenance. They were initially levied to fund NEW road construction. The need for new road construction is purely a function of the number of vehicle miles being generated in a location. Therefore, a tax BY THE MILE makes a lot more sense when funding road construction.
#316 of 331 Wait a Second !!! 'Splain something to me !!!????!!!
Apr 25, 2007 (9:56 am)
With all this talk about "gas tax revenues falling" and how state governments are dealing with the supposed "shortfall" because of less gas tax revenue SUPPOSEDLY because of hybrids and small cars -
from this post:
The POOR Little Taxman !!!
Riddle me THIS Taxman:
1. If overall gasoline consumption is NOT DOWN in the USA (and it's not, according to every statistic I can locate) then WHERE is this MYSTERIOUS LOST TAX REVENUE coming from?
It's not coming from less gas tax, if there is the SAME AMOUNT OF FUEL being sold and used and burned.
How, praytell, are the hybrids and other high mileage cars having an impact of some BILLIONS of dollars if the amount of fuel used is not GOING DOWN?
What am I missing here?
#317 of 331 Re: Wait a Second !!! 'Splain something to me !!!????!!! [larsb]
Apr 25, 2007 (10:51 am)
I don't understand it either. Not only are we consuming more fuel but there are several states that have a percentage sales tax in addition to a per gallon tax. So these states should be doubly benefiting from the current high gas prices, CA for example. You can make the claim that high mpg vehicles aren't paying their fair share but there is no explanation for why there should be a revenue shortfall.
#318 of 331 Re: Wait a Second !!! 'Splain something to me !!!????!!! [larsb]
Apr 26, 2007 (11:28 pm)
Gas consumption is going up. Mileage is going up exponentially to the increase in gas usage. That means more road maintenance etc. Every one in a hybrid is going more miles so they have not solved any of the problems that they were supposed to solve. In So Ca they cannot build roads fast enough to keep up with the demand. More cars driving more miles. It has gotten markedly worse in the last 5 years. Kind of looks like the hybrids are at fault
#319 of 331 Re: Wait a Second !!! 'Splain something to me !!!????!!! [gagrice]
Apr 27, 2007 (6:17 am)
Mileage is going up exponentially to the increase in gas usage
That is simply not true. If it was then the nation's fleet efficiency would be going up. It isn't. In fact it is slightly worse than it was 20 years ago. If you compare today's fleet to 20 years ago you will see for every hybrid driver paying less in fuel taxes there are now several truck and SUV drivers paying more. While a legitimate argument can be made that the driver of a high mpg vehicle isn't paying his share from the government's perspective their bottom line should not have suffered. Also I'm not sure construction costs are linear. Is a 4 lane highway really twice as expensive to build as a 2 line highway? I doubt it. If the government is blaming this revenue shortfall on hybrid drivers it is somewhat of a red herring.
#320 of 331 Re: Wait a Second !!! 'Splain something to me !!!????!!! [gagrice]
Apr 27, 2007 (6:19 am)
Gary says, "Gas consumption is going up."
Well, that would not be because of the hybrids. The effect is OPPOSITE. Someone who trades a 20 MPG SUV for a 40 MPG hybrid would have to drive MORE THAN TWICE AS MANY MILES per year to have a net effect of raising gas consumption. I don't see that scenario happening on a large enough scale to be making a difference.
Gary says, "mileage is going up exponentially to the increase in gas usage."
I don't see that either. I found a web page the other day that said the average US driver still drives about 12,000 miles a year, not a huge jump from recent years. So if people aren't SUBSTANTIALLY driving more miles, then the highways CANNOT BE SUBSTANTIALLY being negatively affected to the point of needed more maintenance than usual. In 1990, the average car on the road traveled about 11,107 miles a year. In 2005, each car traveled about 12,084 miles annually. So if it only jumped 9% in 15 years, how much could it have possibly jumped since 2005?
Gary says, "in SoCal they cannot build roads fast enough."
Gary, I spent two and a half years in SoCal in the early 1980's, and they had that same problem back then too. It has nothing to do with higher mileage cars.
Gary says, "everyone in a hybrid is going more miles...looks like the hybrids are at fault."
That is just a patently amazing statement to make. Any facts or studies or web sites to back that up, or is that just your "feeling?"
Me personally, I've had two hybrids and I have driven fewer miles combined in the last three years than I did with my Avalanche the one year before I bought my HCH.
So mark me off your imaginary list of "hybrid drivers who are driving more miles" because they own a hybrid.
Bottom line is this: The high rate of oil usage in the U. S. is due in part to the fact that we’ve allowed too many low-mileage vehicles on the road - not too many HIGH MILEAGE vehicles on the road. Be sensible.
#321 of 331 Re: Wait a Second !!! 'Splain something to me !!!????!!! [larsb]
Apr 27, 2007 (3:19 pm)
"What am I missing here?"
Try imagining your dream scenario - everyone drives a Prius. How much will the Government then bring in from the fuel taxes (the money that is supposed to pay for road maintenance)? At the same time, the Prius (Priusii, Priusses? - that the heck is the plural anyway?) still use the roads.
For the same mileage, an efficient hybrid will use less gas (and contribute less money to highway funds) than an equivalent gas guzzler.
This is not to recommend people buy gas guzzlers, it is a comment upon reality. Eventually, they are going to have to find some other way to fund the highway costs, because I believe that higher MPG is in the cards for the future (in the form of hybrids, clean diesel, or other technologies).