(FWD, Frost Tube,
Thaw Index) 24%
a. Placing load restrictions.
(FWD Frost Tube, Thaw
Date or Time Limit 29%
b. Removing load restrictions.
Figure 4. Methods for determining when to place and remove road load restrictions.
index) to place load restrictions (Fig. 4a); only 14%
tative techniques, stated that they were comfort-
use quantitative methods to remove load restric-
able about the start of the load-restricted period
tions (Fig. 4b). The remaining 10% who use such
(the start of thaw is well defined: temperatures
over 0C [32F], loss/reduction of frozen layer,
methods simply keep restrictions in place for a
specific length of time or remove restrictions
sudden decrease in pavement deflection or stiff-
subjectively. Approximately one-quarter of the
ness as measured using an FWD, etc.). However,
responding states use dates to impose restrictions.
as observed in pavement engineering studies,
Several states, particularly those using quanti-
recovery is not well defined. This is reflected by