Ok, impossible to make 100% safe, but having a venue where there is only basically one entrance for 1.5 million people just shows planning on an idiotic level- Everyone I spoke to in Germany who is involved with events had a fair idea something like this was going to happen, as saddened as they were by the turn of events, they were not surprised..
The organisers (who I should add, are Mc Fit, a german gym chain, NOT Dr Motte, the originator of the love parade) were apparently putting a lot of pressure on the city authorities to stage the event despite concerns for the safety of the venue..