PHASE II REPORT - Caltrans

Ride quality has been shown to impact the rate of deterioration of pavements. It is
recommended that the surface of the pavement be smooth and provide an excellent ride level to
reduce the effects this may have on individual sections within a test site. As a target, the
existing surface should have a prorated IRI of less than 100 inches per mile (2540 mm per
1609.3 m) as measured by a calibrated profiler.
A site will be required in each of the four climatic regions. The current project States provide
this diversity of climate regions. The four climatic regions used by the LTPP program were Wet-
Freeze, Wet-No-Freeze, Dry-Freeze, and Dry-No-Freeze. These regions were determined by
the amount of average annual precipitation and duration of freezing temperatures during an
average year. The type of climate has a significant impact on the selection of the mix. In warm
and dry climates, the rate of evaporation is greater and slow setting emulsions are desired. The
opposite is true of wet and cold climates. The rate of curing can be altered by the amount of
water, cement, emulsion, and set control chemicals. The four climatic regions will provide an
opportunity to apply different mix designs using the new recommended procedures.
The effects of traffic also have an impact on the rate of deterioration. Traffic loadings may be
determined in many different ways; unfortunately, there is no consistent national traffic loading
reporting scheme. Many States do not utilize a consistent traffic loading procedure. The most
prevalent way to express traffic loadings is the Equivalent Single Axle Load (ESAL), which is
based on Average Daily Traffic, Percent Trucks, Truck Factors, and other conditions. Another
way is to express traffic applications as Average Daily Traffic (ADT) with a certain percentage of
trucks. Other States use a Traffic Index based on ESAL values. Slurry seals and microsurfacing
are preventive maintenance treatments and are not used as enhancements to the
structural capacity of the pavement. Because ESAL values are used primarily for the structural
design of pavements and utilize an ADT and percent trucks, the expression of ADT and percent
trucks is recommended to express traffic applications.
Table F-3 presents the recommended matrix factorial for site selection. The amount of traffic for
the factorial has been divided into two levels: high and moderate. The high traffic level ranges
from 25,000 ADT and above (>10 Million ESALs). The moderate traffic level ranges from
10,000 ADT to 25,000 ADT (approximately 4-10 Million ESALs over 20 years with 10 percent
trucks).
The variation of the type of subgrade soil and base materials (and their properties) between
different sites will have an effect on the structural performance of the roadway. The costs
associated with sampling and testing these materials at each site location is considered
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