A couple of years ago there was some major road works near me that made one road one way, so all the traffic was going on my normal bike route to work - on which there's a primary school with the usual Karenesque car dropoffs going on blocking one lane of the road. The result - a traffic jam a full 4 miles long every morning.
The weather was absolutely beautiful - one of those perfect September spells of settled weather, no wind, not hot enough to make anyone sweat at a steady riding pace but not cold enough that you would feel cold. The schadenfreude I felt passing this line of traffic on my bicycle was exquisite.
What was more puzzling is that literally none of these people (all one person per car) dug their bikes out, even though judging by which turn at least half the traffic was taking, most of the journeys were under 5 miles.
It's incredible, isn't it? They're digging up the local "arterial" (it's too small to really be an arterial route, but it certainly carries that much traffic) to install some fibre (finally!), so it is down to one lane, and you can imagine the jams that have ensued.
The thing is, we're a whole 4 miles out of the city centre, and again, based on the turnings people are taking, I know most of the traffic in the morning is heading into town, and yet no one seems to think that perhaps a bike or bus would reduce the traffic and make the journey quicker for everyone involved.
Obviously none of the people in the cars you are passing are using their bikes that day, but how many of the cyclists on the road would have otherwise used their cars?