I thought this might be an interesting thing to start....basically anything (in theory with a Swiss slant on it )

What does T.I.R. stand for on the back of lorries [trucks]?

Transports Internationaux Routiers - it means that they carry a sealed cargo from country A to country C and when travelling through country B, can pass customs in a more simple manner.

What does the S mean on the back of some lorries?

Spedition, I believe. So effectively, when you see the lorries being filtered into certain lanes but some seemingly ignore this rule, they're carrying the S and are local cargo haulers.