Well last wed I had observed this in the gzb-cnb zone. The freight trains in opposite direction sometimes could be seen running at quite high speed in the thick fog compared to my rajdhani. I was wondering then why the freight could run at higher speed but the rajdhani couldn't. If the freight could run well, surely a higher speed was manageable in thick fog than the 20kmph speed which the rajdhani was allowed. It was clear that freight was being given more priority.