What should you do before using one launching girder?

When a bridge will be constructed, one launching girder comes out in my mind natually, which may be professional sense.

Actually before deciding using one launching girder, below factors have to be considered:

1. a precast yard for pre-cast girders to be pre-fabricated and a lifting station for precast-girders to be lifted onto the girder carrier. If there is no enough space to build a precast yard, then it has be to re-considered whether the launching girder is proper;

2. To lift and carry pre-cast girders, gantry crane and girder carrier are necessary;

3. Whether the bridge abutment has enough space allowing assembly of launching girder;

4. check and re-check loads of launching gantry and girder carrier, ensure whether the bridge deck could bear loads from them.