The folders contain instantaneous travel times that are calculated using real time data. 

The link speeds at the beginning of the time period are used to calculate the trip travel time.

The resulting travel time is corrected by using the difference between the historical average times at the beginning and of the trip. 

The speed data is measured at 5 minute intervals.

A better way to calculate travel time is to start at the beginning and then use the next 5 minute data set as the calculated travel time increases every 5 minutes.  In the real time data, we do not have the next time slice of data since it occures in the future.  

We find a very good correlation between the two types of travel times. 

WSDOT is providing this archive of real time calculated travel times becuase we already have the data. Not so much that we believe they are the best travel times.  Calculating the travel times from the archive data is difficult and processor intensive.  

NOTE: THE ROUTES WITH "TT" AND "VMS" IN THE NAMES ARE NOT INCLUDED PAST APRIL 2021.  THIS CORRELATES WITH OUR AUTOMATED UPDATES.  THE "TT" AND "VMS" STAND FOR VARIABLE MESSAGE AND TRAVEL TIME SIGNS.  THESE ROUTES ORIGINATE FROM OUR THE SIGN LOCATION.  THE MAIN ROUTES ORIGINATE FROM ON AND OFF RAMPS AND ARE CONSIDERED MORE USABLE.