The corresponding author has developed a new, simplified tour-based model for the Charlotte, NC area. This model is generally similar to the activity-based model structure used in other large areas but incorporates several simplifying assumptions that make it less rigorous but significantly easier to calibrate and apply. One feature of all such models is an intermediate stop model, estimating the locations of stops between the tour origin and destination points. In early versions of the simplified approach, these stops were treated as being independent of each other. That is, the location of stop 2 was not influenced by the location of stop 1. This is probably less accurate, but was done for the sake of simplicity. This method was improved for the Charlotte model, in which the sequence of stops was found to be relatively important. The Charlotte stop location model has nine stratifications:
1. Work, stop 1, lower 50% of income
2. Work, stop 1, higher 50% of income
3. Work, stop 2
4. School/University, stop 1
5. Shop/Other/At Work, stop 1, lower 50% of income
6. Shop/Other/At Work, stop 1, higher 50% of income
7. All non-work, stop 2
8. All purposes, stop 3
9. All purposes, stops 4-7
This stratification was influenced by the number of available records and preliminary analysis of stop sequencing. The principal system variables are: detour time, area type, distance to the CBD center, employment accessibility, time from the last stop, and stop-to-tour destination time. Size variables are also very important, mainly retail employment.
The authors displayed a small sample of actual tour/stop records graphically to see if any patterns were evident, but none was found. The stop locations and sequences appeared largely random. However, the “time from the last stop” variable was statistically important, suggesting that the location of stop N+1 is indeed influenced by the location of stop N, at least for the first 3 stops (where sufficient data existed to make that determination). The results of the model estimation suggest that stop sequence number is at least as important as the tour purpose, if not more so.