I tried to do the same in 2015 (blablacar for packages, startup name was tomandgo) and we couldn't solve that problem, it is genuinely hard.
I think in our case the main problem was incentives, we were suggesting low prices for the people sending packages but we forgot that the drivers need an incentive to drop it.
I think in our case the main problem was incentives, we were suggesting low prices for the people sending packages but we forgot that the drivers need an incentive to drop it.
Best of luck!