Clear detritus from the road, or wait for the police?

I had an odd experience yesterday. While driving from Stratford to Solihull I joined a long queue of traffic on a 50mph section between built-up areas. We edged forward, and it became apparent that there was something blocking one side of the road. It was rush hour, and traffic in my direction was having to wait for kind opposing souls to leave them a gap to swerve around. As I got closer I could see a bunch of stuff that looked like it had fallen off the back of a truck: bits of wood, crates, netting etc..

I thought this was a bit silly, so pulled over and started dragging it all onto the thankfully-wide pavement. I heard a couple of other car doors open as if people were coming to help, when a guy appeared and told me that the police were on their way and I should leave it for them to see. By this time the queue was stretching well into the distance. I tried to clear a little more and he again told me to stop, because he’d called the police, and waved other people away. At the time I assumed he must know something about the protocol, so got back into my car and drove off. But within a couple of minutes I’d decided that was dumb. It’s not like it was a crime scene – there was no accident – and surely the police would only have cleared it themselves? It’s bizarre that somebody actively stepped in to stop us clearing the road. Why would you do that?