For the terrestrial, it is logical for the bordering countries.
For the air is so small volume and speed.
For the maritime you have no choice for long distances and high volumes
It sometimes happens that the question arises, it is then necessary to choose by priority between speed, volume and price:
Example 1: Dakar-Niamey for 30m3 (A 20" container)
Advantages: maybe the price, responsibility of the shipping company between Dakar and Niamey terminal.
Disadvantages: Very long.
Disadvantages: Very long truck trip through Africa, more risk and road damaged in places.
Example 2: Dakar - Paris for a small volume
Advantages: if in summer in groupage period, the price will be interesting, no problem for the weight, it has a margin of 1 or 2 m3.
Disadvantages: The weather, and if it is out of groupage period you will be obliged to take a complete container (thus the price).
Advantages: Speed, anytime in the year and sometimes the only solution.
Disadvantages: The price which reaches the cost of a complete container as soon as one exceeds 4 or 5m3, the weight, the size of certain parcels according to the type of plane.