Michigan’s unique truck-weight law
Michigan’s Unique Truck-Weight Law
Michigan Department of Transportation, Bureau of Transportation Planning, Intermodal Policy Division, May 2, 2012
Trucks are a critical component of Michigan’s economy. Trucks carry about half of all freight tonnage moving in Michigan. (Railroads and Great Lakes freighters each carry approximately one quarter of the tonnage each). Trucks carry the majority of Michigan freight by value.
Michigan has a unique system of truck-weight laws which allows greater maximum gross vehicle weight (GVW) than in other states. (Gross vehicle weight includes the weights of the truck, cargo carried, fuel, and driver.) Maximum allowable axle loadings are the same in all states, including Michigan.
History
Before World War II, Michigan did not limit the number of axles that could be used on trucks. Between 1942 and 1967, there were limits on overall length and per-axle loading, limiting vehicles to a maximum of thirteen axles and a gross weight of 169,000 pounds. Since 1967, the maximum number of axles has been limited to eleven, and peraxle load restrictions have resulted in a maximum gross vehicle weight of 164,000 pounds.
Since 1982, federal law has required all states to allow gross vehicle weights of 80,000 pounds on the Interstate system and other designated highways, and for certain distances off these highways en route to terminals. These 80,000 pounds are typically spread over only five axles, including a three-axle tractor with a tandem-axle semi-trailer—the familiar “eighteen-wheeler” combination.
Michigan and several other states allow gross vehicle weights greater than 80,000 pounds, when spread over more than five axles. These weight laws are allowable under “grandfather clauses” in federal law, but if these laws are repealed, they may not be re-enacted.
Axle Loadings and Michigan Law
Michigan’s truck-weight law is designed to control axle loads instead of gross vehicle weight. Research conducted by the American Association of State Highway and Transportation Officials, the Michigan Department of Transportation (MDOT), and other organizations, has shown that pavement damage is directly related to axle loadings, not gross vehicle weight. Michigan limits the weight allowed on individual axles, depending upon the spacing between them, with a maximum of eleven axles.
The maximum gross vehicle weight allowed on a “federal-weight-law truck” is 80,000 pounds, with four of its five axles carrying 17,000 pounds each and the steering axle carrying 12,000 pounds. The calculated maximum allowable gross vehicle weight on the heaviest “Michigan-weight-law truck” is 164,000 pounds, which can only be achieved by use of eleven properly-spaced axles. Most of these axles carry only 13,000 pounds each. The alternative to a single Michigan combination carrying 160,000 lbs. on 11 axles is two standard trucks carrying 160,000 lbs. on 10 axles. Pavement research has shown that these two smaller trucks actually cause about 60 per cent more pavement damage than does the single heavier truck, because of their higher axle loadings and the extra weight of additional tractors at about ten tons each.
Population of “Michigan-Weight-Law” Trucks
In 2011, there were 86,604 trucks registered under elected-gross-vehicle weight in Michigan, according to the Secretary of State. Of these, 8,478 were registered to carry over 80,000 pounds, and 3,972 were registered to carry over 145,000 pounds. Only 9.8% of trucks registered in Michigan actually can be heavier than Interstate-standard “eighteen wheelers.” Many trucks operating in Michigan are registered in other states or provinces and the vast majority can carry no more than 80,000 pounds. As a result, it is estimated that no more than 5% of all trucks using Michigan roads carry more than 80,000 pounds when actually operated.
Annual Elected Gross Weight Number Registration Fee
0 to 66,000 lbs. 72,008 $491 to 1,398
66,001 to 72,000 3,244 1,529
72,001 to 80,000 2,874 1,660
80,001 to 90,000 1,126 1,793
90,001 to 100,000 976 2,002
100,001 to 115,000 959 2,223
115,001 to 130,000 776 2,448
130,001 to 145,000 669 2,670
145,001 to 160,000 3,201 2,894
160,001 to 164,000 771 3,117
All elected-GVW trucks 86,604
The operating weight of trucks is not known with precision. It is not known how many truck-miles are traveled by trucks of various weights, and trucks frequently carry less than their elected gross weight. Michigan trucks that carry only farm produce, milk, or logs pay greatly-reduced registration fees not based on gross vehicle weight. There are 40,120 such trucks; it is not known how many farm, log, and milk trucks operate above 80,000 pounds.
Economic Benefits
While the number of trucks operating under Michigan’s axle-weight law is relatively small, they are extremely important to basic industries in this state. The primary users of heavier trucks are the manufacturing, mining, forestry, agricultural, and construction sectors. Specific commodities hauled include automotive and other sheet steel, structural steel, factory tooling and other metal products, automotive power trains, stone and aggregate, cement, asphalt pavement, petroleum, logs, lumber and other wood products, fertilizer, milk, and sugar beets and some other field crops.
The Michigan Department of Transportation has designed our pavements and bridges to safely accommodate trucks conforming to our axle-weight law. Our axle-weight formula results in less pavement damage and a more productive and efficient transportation system.
Michigan industries and businesses are more competitive due to our truck weight laws. Freight rates are lower in Michigan for commodities that can use our heavier vehicles because fewer vehicles, drivers, and trips are required. Rates for these commodities have been estimated to be up to 50% lower than those found in adjacent states. In addition, less fuel is burned to transport the same weight of cargo, and there is less traffic congestion and less crash risk exposure from fewer vehicles.
Because of market patterns of the commodities hauled, Michigan-weight-law trucks have limited backhaul opportunities. That is, trips are frequently one-way movements of cargo with an empty return. (Examples include logs from the forest to pulp or lumber mills, petroleum to retail service stations, and construction materials from suppliers to construction sites.) As a result, these bulk-commodity haulers operate empty roughly half the time, causing minimal highway wear. The lack of backhaul opportunities means it is important for those industries to move their products efficiently, by using the fewest number of trucks making the fewest trips possible.
Significant road construction and maintenance savings are realized as a result of reduced transportation costs of stone, cement, asphalt, and salt used on public highways.
Michigan bridges are designed to carry the concentrated weight of Michigan trucks. If Michigan were to impose federal-standard truck weights, the state would waste the considerable investment in bridges designed to carry heavier, more productive trucks, and basic industries would lose a significant cost advantage of locating in this state.
Safety
The use of heavy trucks under Michigan’s axle-weight law enhances highway safety. There are fewer trucks on the road because each 164,000-pound truck can carry the cargo of about two and a quarter 80,000-pound trucks. Without Michigan’s axle weight law, an additional 10,000 to 15,000 trucks would be on our highways, resulting in a greater exposure to traffic crashes.
Vehicle braking capability and resistance to overturning are improved by having more axles and wheels, each of which is equipped with brakes, and by carrying lower weight per axle.
Congestion on Michigan’s highways is reduced because fewer trucks are required to move our freight. Each truck occupies roadway space equivalent to approximately four automobiles. This is particularly important in urban areas where many users of heavier trucks are located.
Trends
National trends in regulation and research are toward lower axle weights and higher gross vehicle weights. There is some possibility that when the federal-aid highway program is reauthorized, federal law will permit longer and heavier trucks on the national network. Although that appears unlikely to happen in 2012, it is likely that someday more of the nation will emulate Michigan’s approach to truck weight law.
The Transportation Research Board (TRB) analyzed a concept, referred to as the “Turner Proposal,” to allow larger gross vehicle weights spread over more axles, with each axle carrying less weight than currently allowed under federal law. This is the philosophy adopted by Michigan. The TRB concluded that use of such vehicles would result in a net decrease of $326 million in annual pavement and bridge costs nationally. Shippers and businesses would save an estimated $2 billion annually in transportation costs.
States and provinces bordering Michigan also allow certain vehicles heavier than the federalweightlaw trucks. Ontario allows nine-axle vehicles carrying a total of 140,000 pounds. Ohio, Indiana, and Wisconsin issue permits allowing heavier Michigan-style trucks to travel on selected highways. This allows access by Michigan shippers to the steel industry in Gary, bulk rail and marine terminals in Toledo, and the forestry industry in northern Wisconsin. Other states along the Canadian and Mexican borders increasingly allow heavier trucks from their neighboring countries.
In Canada, the provinces of Ontario, Québec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland have recognized the importance of uniformity with Michigan law. Because of their large volume of trade with Michigan they are working to establish more uniform truck regulations. The North American Free Trade Agreement (NAFTA), signed by Canada, the United States, and Mexico, requires efforts to harmonize regulations relating to truck sizes and weight. Canada and Mexico allow trucks heavier than 80,000 pounds. Canadian provinces generally allow heavier axle loadings, while Mexico does not regulate axle loadings, only gross vehicle weights. MDOT is participating on NAFTA committees addressing these issues.
Impacts of Adopting the Federal Weight Law
Periodically there are suggestions that Michigan should adopt federal weight law and reduce gross vehicle weights. There would be several impacts of such action, including—
- more trucks on Michigan’s roads
- greater roadway congestion, particularly in urban areas
- more crash exposure as a result of more trucks
- increased costs to Michigan consumers for goods such as gasoline, milk, lumber, agricultural products, and products containing steel
- decreased competitiveness for Michigan’s steel, manufacturing, mining, forestry, and agricultural industries due to increased transportation costs
- more damage to pavements due to increased axle loadings
- increased costs for building and maintaining roads
Summary
The Michigan Department of Transportation believes that Michigan’s truck weight law is based on sound research and results in less highway damage and improved safety relative to federal weight law. Several of this state’s key industries benefit by being able to transport their goods much more efficiently and economically. Recent trends and studies suggest that the federal government and other jurisdictions are beginning to recognize the validity and benefits of the approach Michigan has used for decades.
