5. The Truck
The dumpster truck relates to the positioning theory. The grid mapped out on the floor is all about the placing of the fall. The truck being in the way of John's vision, as you can see above, helps with this. But more importantly than that, it gives Sherlock the opportunity to escape - if of course that
isn't him on the pavement - or, it's where a mattress comes in. It's understandable to sceptical of the mattress idea - we saw him hit the floor - but a getaway vehicle is more than possible. Or, the truck's just there to block the view for John. If it's not important though, why did Sherlock wait until it had arrived? Why didn't he just jump when the bus was there?