I’m home now… confirmed that footfall is linked to settlement prestige, as follows:-
| Prestige | Settlement Size | Footfall |
|---|---|---|
| < 10000 | N/A | 0 |
| 10000 | Outpost | 20 |
| 50000 | Hamlet | 30 |
| 250000 | Village | 40 |
| 1250000 | Town | 60 |
| 6500000 | City | 80 |
| 32000000 | Great City | 100 |
Footfall per player can only be generated per 24 hours, so one player visiting twice in one day only generates footfall once in that 24 hour period.