I recently decided to finish toying with a spreadsheet using the formula given to my by Humanophage to determine the time spent collecting and delivering materials by the level of the building. The formula given was

The (DA) represents the time whilst under the Protection of Kresp (Dark Aura), the base time for Metal was estimated using the formula as I did not have a Mine built and producing when I had a non upgraded Factory or Roads building.

Factory building level and Collection times


Roads building level and Delivery times (This data assumes delivery of Wood and Stone from one tile adjacent to your city. The Values are set for that, the Metal delivery are ineligible as mines may vary in distance from your city. For more accurate information, use the formula above.)



So far those numbers are almost identical to what I see in game, with some minor fluctuations.

Edit: Posted images, code was all ugly.

Edit 2. Realised my error in the data for Roads not reflecting deviations in distance from the city. Added a disclaimer.