My question is related to freight transportation, but I am stuck on the logic. So, I am considering a path between two points $(a, b)$ where I am sending $n$ trucks where the capacity/truck is $k$. The distance is $d$ and the truck speed is $v$. Let's say that I am trying to get the time required to transport one unit of freight, do I use the standard $ t_{a,b}=\frac{d_{a,b}}{v}$ or do I consider road capacity (i.e., $path \ cpty_{a,b} =\frac{60}{headway}$)? If I consider $ t_{a,b}=\frac{d_{a,b}}{v}$, and assuming that $n$ vehicles are not simultaneously dispatched, then which is it ? The time to transport one unit of freight, $k$ units of freight ? Finally, do I need to use queuing theory to compute the total time to transport $k \times n$ units of freight ?
An example would be a minimum flow time model where the objective function is to minimize the total amount of transit time or $Min \ Z= \sum_{a \in O}\sum_{b \in D}t_{a,b}x_{a,b}$, where $t_{a,b}$ is the average time to transport 1 unit of flow over any $(a,b) \in A$ and $x_{a,b}$, the total flow transiting through any $(a,b) \in A$. If I have to solve it, I would need to be able to accurately define a function to compute $t_{a,b}$.
