Fig. 11.25 Recommended treatments from successive runs on 25-26 January.
11.3.4 Verification report for January 16-17 cold rain event
The January 16-17 event is the earliest of the verification case studies and occurs just
prior to full operations of the GPS/AVL equipped maintenance vehicles. As such, actual
DOT operations were estimated from observer reports and garage logs. This event was
primarily a rain event with marginally warm roads. Fig. 11.26 shows the forecasted
precipitation and road temperatures for the I35N route in Ames, IA. Rain was predicted
to fall from 1600 (4PM on the 16th) until 0600 on the 17th. Road temperatures were
expected to remain above 33.5 F throughout the 48 hour forecast period. Not surprisingly,
the MDSS did not recommend any treatments for this route and the Iowa DOT didn't
perform any. However, the forecast for the US30 route in Ames was just slightly different
with the road temperatures expected to slip just below the threshold of 33.5 F. This
temperature drop occurred after the precipitation was forecasted to stop, but before the
road surface was expected to dry out. Consequently, the MDSS recommended a treatment
at 0500 on the 17th to protect the road from freezing.
Garage logs and post-event discussions with the Ames personnel determined that the
US30 route was indeed treated just after midnight on the 16th. Supervisors felt that the
roads were in jeopardy of freezing after the end of the precipitation, but applied the
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