One thing that many people miss about adjustable inserters is that their performance may be greatly increased by minimizing its arm travel length. For example this configuration is 3 times faster than a standard one.
The usual way to unload a train is to place a 1 or 2 (+~70% faster) rows of 6 inserters. Third row adds only ~15% so not many people are using it.
Here is an alternate way to unload a train by minimizing inserter arm travel length using only 4 inserters (bottom part)
In my tests those 4 inserters already beat 2 row configuration at the top. From there you can fetch items by logistic robots or unload them on a belt. You can easily increase storage capacity by adding chests like so
Increased buffer
If you want to go over the top with this you can make something like this which increases unloading speed by additional 150%
Moar inserters
Make sure to configure your inserters (pickup and offset) so that they only rotate without arm extension (because rotation is way faster). Like this for my example
Config
I performed my tests on basic stack inserters with stack size of 10. My Factorio version is 14.08.
