Skip to comments.Viewpoint: Limit highway damage by limiting weight loads trucks can carry
Posted on 04/06/2010 11:53:39 PM PDT by Tolerance Sucks Rocks
The "American Heritage Invention and Technology" magazine has an article on interstate highway bridge construction. The article was prompted by the collapse of the I-35W bridge in Minneapolis a few years ago.
The legal weight limit for semi-trucks was quoted as 80,000 pounds. This weight limit is what interstate highway construction in America is designed to carry. The article also mentioned that Nevada has found one in 14 trucks exceed the 80,000-pound legal limit. It was not clear from the article if the legal limit of 80,000 pounds is a federal limit and applies anywhere in the United States or not. Interstate highway construction has a limit of gross weight that the roadbed is designed to carry.
The state of Michigans legal gross weight limits for semi-trucks can go as high as 164,000 pounds, if the rig has 11 axles. If the rig has six axles, the Michigan legal limit is 101,000 pounds. Michigan has the highest gross weight limits of any state in America! Interstate bridges in Michigan are being damaged by the huge weight limits that Michigan allows. Interstate I-94 runs through southern Michigan and has extremely heavy semi-truck traffic.
About 16 years ago, after the upstate New York interstate bridge failed, the Michigan Department of Transportation told me that there is a ten-fold safety factor built into interstate bridges. This brings the allowable total to 800,000 pounds gross weight if the legal limit is the 80,000 pound limit quoted in the article. On the other hand, the possible total weight that a four lane, Michigan interstate highway bridge with a semi-tractor trailer on each of the four lanes might have to bear is four times 164,000 pounds, which comes to 656,000 pounds gross weight.
The Michigan Department of Transportation also told me that each time a truck passes over a bridge there is a slight flexing of the bridge. I was also told that the effect of the flexing, rust and other factors might reduce the safety factor in Michigan by an unknown factor. Who decides if the detection of overweight trucks is important enough to save our highways and avoid taxes to fix the damage done by overweight trucks?
Michigan is in the midst of an economic downturn. Repairing the interstate bridges is not realistically possible but it is possible to reduce the huge weight limits that Michigan has set as legal limits.
The recent NAFTA superhighway that is in the news has a branch that uses the Michigan portion of I-94 as part of the NAFTA highway. It is no wonder that domestic and foreign truck companies want to travel I-94 because they are allowed to carry double the gross weight limits in other states. The taxpayers of Michigan are paying for the damage to highway bridges and pavement caused by outlandish semi-tractor trailer weight limits. I have seen trucks in downtown Kalamazoo with a map on the drivers door of Mexico and America altered to show Texas, New Mexico, Arizona and Lower California as part of Mexico. I have also talked to a driver at the rest-stop on westbound I-94 in Galesburg who told me Canada, US, Mexico all same, no borders.
Railroads have never made a successful business carrying only passenger traffic (possible exceptions are local commuter trains.) The supposed highspeed rail line from Chicago to Detroit and Canada is really intended for bulk freight traffic which is the real moneymaker for railroads. Rail traffic using bulk loads will take business away from semi-tractor trailers which then will reduce damage to our interstate highways.
Dennis Weber resides in Kalamazoo.
Recently in Wisconsin truckers were blammed for the rapid detioration of the Zoo Interchange. Nevermind the fact that Mayor Barrett and Governor Doyle have stonewalled any construction and have barred contractors from putting in bids. Nor do they want an expansion to a 4 lane freeway, instead they want trolleys, lightrail, highspeed rail, and more busses.
It doesn’t pay to elect Democrats.
Three factors at work here. One is the weight per tire. Another is the frequency of weight per given area and the Third is the resistance of the road to weight.
This only addresses #1. Number 2 needs to be addressed by improving (reducing) the traffic density. This can be done by increasing the number of lanes, making use of road to rail options, restricting the hours of use by tractor trailers, etc.
Third option is to improve the specifications for how we build roadways. This would increase the cost of building roads but make them more resistant to loads.
For some structures, a good heavy weight periodically makes the bridge last longer. In steel, fatigue failure is associated with crack growth, and a heavy weight causes crack tips to blunt, and work hardens the crack tips, so that a crack has to re-initiate before it can propagage again. I know that is not considered in Miner-Palmgren linear damage calculations, but failure is complex and non-linear.
Actually, four factors at work here. The fourth is the factor of having the highway "trust" fund spent dry on trinkets for welfare brood mares, totally unrelated to highway construction and maintenance, in order to re-elect Democrats.....
Having just done a 4500 mile cross country trip I can tell you that the interstate highways we encountered for most of our journey were in terrible shape. Especially Oklahoma and New Mexico. I-40 in Oklahoma was so bad it almost prompted me to write the ODOT people to ask at what point do they consider the threshold for repaving? The stretch going through OKC and points east are quite possibly the worst stretch of interstate I've ever driven on (and I've driven in 49 states).....
Also, roughly a sixth of the gasoline tax money is devoted to buses and choo-choos (mass transit systems, no doubt loaded with union employees).
All-out development of our oil resources would put downward pressure on oil prices, and therefore, on asphalt prices. The use of non-union labor in Federal highway contracts would help, too. (I believe the Davis-Bacon act requires such workers to be paid a prevailing union scale.) There are probably other cost-cutting measures that can be taken as well.
Personally, I'd just have the states take over. The Federal government is in deep doo-doo as it is.
However, in lieu of passing the responsibility for roadwork completely to the states, more revenue will then have to be raised for the fund somehow, especially if Oberstar gets his way on transportation. I don't regard tolls or increase gas taxes as being out of the realm of possibility, as long as the resulting revenues, along with the original gas tax revenues, are spent solely on Federal highway projects -- Interstates or U.S. routes.
The tolls, needless to say, should only be imposed on such routes.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.