Full suspension with drop from public bridge?

[StateOfMind]

My goal is instant death so I'm opting for train method or full suspension with a drop.
Near by there is a bridge going across a motorway.
I could pre-tie the noose and put the rig in my backpack then I would just have to make a secure knot for the ligature relatively fast.
There is a ditch so if I get decapitated I wouldn't fall on passing cars.
This would all happen in the late evening.

What would be the ideal rope for this?
If it just snaps my spine and get rescued will I be a veg?

 

[F_Alonso]

I think it would be effective but, at the same time, it's a rather gruesome easy to go. Please reply to my private message as the are possibly other ways to achieve your goal.