When the traffic lights go out
When the traffic lights stop working, traffic still flows. Some drivers go for, some are a little hesitant, but they all know the rules so they figure it out. Traffic flows more quickly because drivers don’t have to wait for an artificially created gap in the flow, if they see a naturally occurring gap, they go.
That is, until it doesn’t flow. When one of those drivers gets it wrong and causes an accident, it all grids to a halt.
Traffic lights bring greater safety at the expense of the flow of traffic (at that location at least. Good traffic lights design should prevent longer delays elsewhere). They work this way because safety is prioritised over the speed of flow. So what if lots of drivers have to wait a few seconds as long as that one driver who might have otherwise been in an accident doesn’t get hurt.
That’s why the “flow” part of “fast flow of work” is so important. Traffic make things slower but make the flow safer and more reliable.