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NS764: Improved seasonal load limits
Problem
Spring Load Restrictions (SLR) are an important tool that local agencies use to extend the useful lives of their pavements. MnDOT uses a method defined in Engineering Services Division Technical Memorandum No. 14-10-MAT-02 dated October 7, 2014. The equations for calculating the cumulative thawing index (CTI) provide a reliable proven scientific method for accurately setting the start dates for SLR. The method for removing SLR is not as well defined or documented. It is defined by MnDOT as follows:
“The end date of the load restriction period for each frost zone is determined using measured frost depths, forecast daily air temperatures, and other key indicators at several locations within each frost zone. The speed with which the soil thaws is dependent upon several variables including maximum frost depth, soil moisture content, and spring weather patterns. Therefore, the duration of the spring load restrictions will vary from year to year. However, it is MnDOT’s intent that the spring load restrictions last no more than 8 weeks unless extraordinary conditions exist that require additional time or route specific signage.”
Given all the variables listed above it is apparent that more work needs to be done to improve the process by which end dates are set. New computational tools can be developed that consider which variables have the most impact on setting end dates. Also, there are new sensors that can measure in-situ material properties. The sensors could be used to determine in real time when SLR could be lifted. Many options and even a combination of those listed could be used to more effectively set SLR end dates.
Removing SLR too late causes a negative effect on our economy by limiting the flow of trucks to their destinations. Removing them too soon causes unnecessary damage to our road network.
Objective
Improved methods to ensure that SLR end dates are set as accurately as possible with the most current technology and processes available.
Expected outcomes
- New or improved policy, rules, or regulations
Expected benefits
The numbers 1 and 2 indicate whether the source of the benefit measurement is from:
- A specific research task in your project that will be measuring this particular benefit, or
- A separate effort to analyze data provided by the state or local agency involved in this project.
- Increased Lifecycle: (1)
- Accurate placement of Seasonal Load Limits protects our most vulnerable roads from premature damage and ensures that they reach and exceed their performance goals.
- Operation and Maintenance Saving: (2)
- A separate effort to analyze data provided by the state or local agencies involved in this project will ensure that commerce can effectively continue to those areas where roads are restricted. This effort will help maximize the investment of our road system.
Technical advisory panel
- Glenn Engstrom
- Charles Kremer
- Nancy Graham
- 2 - County Engineers
- MnDOT Maintenance