Accident in Limerick traffic chaos

Was travelling into Limerick city this morning and there was a fatal accident at 4.00 in the morning and as a result the Dock Road, a main thoroughfare into Limerick City and also used as a route to getting towards Shannon, Clare and Galway was closed. They were awaiting Garda Forensic team and also neded to clear lorry or lorries not sure from the scene.
There was traffic chaos.
I can understand that this was due to the road being closed.
But what I found puzzling was that all the traffic lights on all the routes into the city were set to flashing red.
Why was this the case?
How does this contribute to improving the flow of traffic.
There were gardai at one or two junctions according to colleagues but not at the junctions I encountered.
To my mind this only added to the traffic nightmare as it meant people had to become more aggressive in order to progress from side roads onto main roads etc.
Does anyone know why this is done and what it is supposed to achieve?

The fact that the road was closed is not the issue.
I understand there was chaos at the scene.
But why were the lights set to flashing red?
What does this achieve?

Perhaps this or another accident damaged the traffic control systems causing the lights to malfunction - i.e. it was not deliberate?

No it was a decision made by the gardai to control the traffic....I just cannot see what this serves.
As for you point Priscilla not sure where you got that information but the reason the scene was protected was so they could judge who was negligent in the accident and the forensics team had to wait until daylight.

Yes I'm very sorry, I did say it may or may not be true, Limerick is deadly for the rumours. I am very sorry indeed if I offended anyone.