Test release for Idea for next version. (http://forum.simutrans.com/index.php?topic=6051.0) topic.
Github branch (http://github.com/inkelyad/simutrans-experimental/tree/loading_speed)
Windows SDL file (http://simutrans-germany.com/patches/download.php?file=sim-ex-sdl-loading_speed.7z)(patches.simutrans-germany.com)
Patch uses loading_time field from vehicle and level from platform to calculate actual loading time.
High-level platforms will decrease loading time.
If you define loading_speed_use_enables=1 somewhere in simuconf.tab, it will use 'enables' bit too.
After that, for example, p****enger-only platform will load goods(and mail!) very slowly.