It is sometimes desirable to use zero-count values for certain time segments in the Avenue assignment; however, the algorithm used by the dynamic estimation process scales data by the count value itself. Thus, zero-count values lead to a division by zero which produces an infinite value. On the other hand, removing the 0 count from the screenline file causes a data alignment problem due to the presence of values in the route choice matrix which are in fact dependent upon the zero count value. In this case, it is recommended that the user either:

1. Remove the zero count screenline from the assignment, or

2. Change the value of the count in the dynamic count file used by Analyst Drive to 0.1.

The first option eliminates the problem at the source, but may not be feasible given the circumstance of the problem. The second option will allow the user to maintain the zero count in the assignment while limiting its effect on the outcome of the estimation. The justification for this is that a 0 or 0.1 count in the overall picture are essentially the same unless all counts are close to 0 or 1. For example, if the initial simulated volume were 10, then matching the count to 0.1 instead of 0 would produce a 99% reduction in the actual error for the particular count value, and the screenline value itself would likely produce a very small contribution to the total error anyway.