NDDOT's procedure for initiation of spring load restrictions on the State Highway System
Based on the following factors:
- NDDOT utilizes load restrictions to reduce damage to roadways caused by heavy loads at a time of year when
highway pavements are most vulnerable.
- The NDDOT sets load restrictions as weather and roadbed conditions require and removes these restrictions when roadbeds are stable enough to carry legal weight traffic without damage.
The NDDOT primarily uses three factors in the posting of load restrictions.
These factors or indicators are:
- Temperature probes in the base layers of pavement sections. As these temperatures approach 32
degrees Fahrenheit, the NDDOT starts planning the posting of highways with pavement sections which do not have
sufficient strength to sustain the transport of heavy loads during periods when pavement base structures are weak.
- Long range temperature forecast. When long range temperature forecasts indicate that low temperatures
are approaching the freezing point, with daily highs in the upper 30's or 40's, load restrictions are planned.
- Falling Weight Deflectometer (FWD). This equipment measures the strength of roadway bases, as well as the asphalt pavement surface. The NDDOT utilizes the FWD to evaluate pavement strengths for purposes of forecasting when load restrictions may be initiated and removed. The data base, generated by the FWD, in combination with long range weather forecasts and area wide moisture conditions, provides the basis for lifting load restrictions.
It has been the NDDOT's experience that the most significant pavement damage occurs during the first four weeks after the onset of spring thaw. This aspect has moved the NDDOT towards close monitoring of weather forecasts and sub-base temperatures to allow posting of load restrictions on short notice with the overall objective of limiting damage to the highway system.