A major road closure

has caused traffic chaos.
The day before yesterday a cyclist noticed something seriously amiss with a bridge that is used as an overpass by the tram line. The bridge crosses one of the busiest roads in the city. The road carries a lot of heavy goods vehicles.
The cyclist did the right thing and immediately reported it. He or she must have managed to convey concern in a fairly urgent way. There were emergency services on the scene very quickly. The traffic was stopped.
Chaos ensued.  
This is a road which bypasses the city centre but goes a long way in both directions.  A good many buses travel along it. Some of them are "express" buses from outlying suburbs. If they change the last part of the route into the city or the first part out it won't matter too much because the buses don't stop for some distance along that road. But, other buses do. The heavy goods vehicles need to find alternate routes - and that adds to the traffic on those roads. Some of those are already too crowded.
But it was none of that which really concerned me. All of that is just inconvenience. It just slows things down. It is infuriating but it should not be dangerous.
What bothered me was something rather different. There is a train line through the hills behind us. It carries goods trains, goods trains of great length. As the train passes through the suburbs the traffic will build up at the level crossings. It can build up for very long distances. On occasions when something has gone wrong and the train has stopped over one or more boom gates then the boom gates further along are also likely to be down. Even with the police called in to direct traffic it can be dangerous - dangerous because, for some people  up in the hills, there is no way out.
If there had been a fire yesterday and a train had stopped or, worse, derailed, and the crossings blocked there could have been a major catastrophe if the traffic had not been able to move freely in other places. It's the sort of nightmare scenario that, yes you could write a book or make a film. 
I thought of all this because I usually time my journey to coincide with a suburban train. I do this because it means that the traffic has stopped and I can get across the road safely and wait for the boom gates to go up.  Where I wait there is a slight rise. I can look back and see the line of traffic grow.  
I did this yesterday as I waited for one of the extra long goods trains to go through. Another cyclist joined me. We had a "shouted" sort of conversation above the noise of the train. He told me how far he had come and how far the traffic had built up from where he started. There would have been much more by the time the train went through. People were getting impatient.
I changed my plans. I did one thing before another. I wasn't going to get in the way of all those people who wanted to get to work first. 
This morning they are saying the situation could last for months. 
Traffic is lighter than usual at present because school does not start again for another week.
I don't think those at the top have thought about this yet.