Tag Archives: load limits

MnDOT Explores the Use of a Unified Permitting Process for Oversize/Overweight Loads

Researchers produced a proof-of-concept for developing a one-stop permitting process that would allow commercial haulers to plan a travel route and secure all required permits from a single source. MnDOT is working to develop a first-of-its-kind, unified permitting process to consolidate the requirements of every jurisdiction in the state into a single, quick-response platform that meets the needs of haulers.

“From a hauler’s perspective, the permitting process can be very cumbersome. Each agency’s application is different as are the general provisions that haulers need to follow,” said Renae Kuehl, Senior Associate, SRF Consulting Group, Inc.

“As carriers, we’re trying to do our due diligence in getting permits. But the current process can lead to significant safety and legal risks,” said Richard Johnson, Transportation Manager, Tiller Corporation.

What Was the Need?

Hauling oversize or overweight freight on Minnesota’s roadway system—highways, county roads, township roads and city streets—requires approval by each governing authority along the route. Roadway managers must review hauler travel plans to make sure size and weight limits for vehicles and loads will not endanger roadway facilities, hauler equipment and personnel before issuing the over-size or overweight permit.

Any single hauling route may require permits from multiple roadway authorities, each with different application procedures and response times. Some governing bodies, MnDOT among them, issue these permits online and can turn them around in minutes. Other agencies issue permits by mail, fax or email, which can take several days.

Haulers, however, may not have time to wait for a permit. If equipment breaks down at a loading site, for example, replacement equipment is needed immediately to meet contract deadlines and avoid paying labor costs for idle workers. A construction emergency may also demand large equipment be towed to a site. In situations like these, haulers often make the trip without appropriate permitting, accepting the legal and safety risks.

What Was Our Goal?

To simplify the permitting process, Minnesota local agencies would like to develop an online permitting application process that would allow permit-seekers to determine routes based on their vehicle and load size, and secure all necessary permits at one time. This research, the first phase of a multiphase study, aimed to determine the feasibility of a one-stop, unified permitting process by studying its technological and operational needs and gathering input from various stakeholders.

What Did We Do?

Investigators worked with the Technical Advisory Panel (TAP) and a group of policy experts from county and state agencies, commercial haulers and consultants to identify audiences with a stake in a unified permitting process. During meetings in northern Minnesota and in the Twin Cities area, investigators and TAP members met with key stakeholders: haulers and representatives from industry organizations; seven MnDOT offices (including Freight and Commercial Vehicle Operations, Information Technology, Maintenance and Geospatial Information); Minnesota counties; the City of Duluth; the Duluth-Superior Metropolitan Interstate Council; Minnesota State Patrol; the State Patrol Commercial Vehicle Section; and a county sheriff’s office.

The research team identified the challenges and needs of each stakeholder and organized the concerns according to policy, process and technology. Then they explored solutions that would allow the development of a one-stop permitting process.

What Did We Learn?

Researchers determined that a unified permitting process is feasible. Policy issues include the need to standardize general provisions statewide, such as travel hours, insurance requirements and warning devices such as flagging needs. For example, currently the color of flags and lettering on banners vary from jurisdiction to jurisdiction; well-framed general provisions could make these requirements more uniform to serve multiple jurisdictions. The information required by each governing authority in its permit applications could also be normalized.

Process issues were about workflow. More than 80 percent of hauler requests are repeat-able: A commercial haul may be run on the same route with the same-size load three times a month for four months and may not require a full reapplication each time. Some agencies rely on paper, fax or emails to receive permit requests; others purchase permit-ting software; still others build their own software. These systems could be made more uniform so they could interact and share information among agencies.

Technology issues called for an interoperable system that could bring together geographic information system (GIS) capabilities and regulatory data that could be both received and shared. Mapping data could identify each permit required along a route being developed, and a portal could allow agencies to share information as well as allow permit-seekers to enter information and retrieve permits themselves. A portal could also integrate different software packages while offering information like Minnesota’s Gopher State One Call digging hotline.

What’s Next?

In Phase II of this project, which has already begun, researchers will develop a pilot portal that allows users to create route plans, identify permits needed and apply for all permits in one action. Investigators will test the platform with a three-county group. If this effort is successful, researchers will build a unified permitting process for use within all jurisdictions in Minnesota.

MnDOT is also enhancing its software for handling oversize/overweight permits and carrier credentials. Transportation Research Synthesis 1704 surveyed state agencies about current offerings.


This post pertains to the LRRB-produced Report 2017-26, “Oversize/Overweight Vehicle Unified Permitting Process (UPP) Phase I,” published August 2017. 

Study to develop bridge load limits for tractors

Minnesota farm equipment is getting larger and heavier, causing strain on rural bridges. However, there are no  nationally recognized specifications for what size and weight of tractors can safely travel over them.

Currently, bridge load limits are based off semi-trucks, not farm machinery, which have much different axle configurations and wheel dimensions.

“Their geometry is atypical; their length, widths are different; they have different suspension characteristics,” explains Brent Phares, director of the Bridge Engineering Center at Iowa State University.

A new pooled fund study led by the state of Iowa is attempting to determine how much stress heavy farm vehicles put on bridges. This data will be used by local agencies to develop weight restrictions specifically for farm equipment.

“It will help limit the confusion of current load posting signs for farmers,” said MnDOT bridge load rating engineer Moises Dimaculangan.

Wisconsin, Minnesota, Nebraska, Oklahoma, Illinois, Kansas and the United States Department of Agriculture are also participating in the study, which is examining three types of local bridge superstructures: those with steel girders and concrete decks; bridges with steel girders and timber decks; and timber bridges with timber decks.

Through physical testing and modeling, the study will determine how different types of farm machinery distribute their loads on the bridge superstructure.

About a half-dozen farm vehicles were tested on 20 different bridges which were representative of those tending to be the most problematic for farm equipment traffic on secondary road systems, Phares said.

Instrumentation measured the response of the structures to the vehicles. This data was then used as a baseline to calibrate analytical models, which could be applied to 250 different bridges and 121 different farm vehicles.

Researchers will develop a generic tractor profile, which represents the worst-case scenario, for use in determining load limits. With the information developed, signs might be able to be added to the bridges, which show a tractor and the weight limit.Collapsed bridge

“I get a number of pictures emailed to me of bridges that have failed with a tractor implement of husbandry on top,” Phares said. “That’s the problem that people are looking to avoid; the goal isn’t to restrict the size of farm vehicles, but to develop better tools for engineers to make sound and solid analyses for the bridges, so they can provide that information to the people who need to have it.”

Phares said a couple previous studies have also looked at farm machinery weight restrictions. One study, from around 2004, took a high level look at the impact of farm vehicles on bridges. A more recent pooled fund study analyzed the impact of machinery on pavements.

Related resources

Research in Progress: Study of the Impacts of Implements of Husbandry on Bridges

The Effects of Implements of Husbandry “Farm Equipment” on Pavement Performance