I graduated and started programming in 1987. I drove a car with no A/C and vinyl seats. I was sweatier getting out of that thing on some mornings than I would be after biking at a moderate pace.
So then there's probably traffic going 40.
No, the traffic is probably going 20 to 25. At least where I would ride with them. Suburbia might be different.
Bicycle trailers are difficult for cars to see in many situations. They're not a good place to drag a child. You can tell yourself whatever you want, but there's just no way to make that safe. In certain limited circumstances the risk may be comparable to other stuff you do daily, but for the most part, it's just a bad idea. I mostly see them in places where it's a very bad idea, that may be confirmation bias, but obviously plenty of people are using them that way.
Describe for me a situation where you can't see a trailer and would be likely to collide with one? The idea that you could see a kid on a bike easier than you could see something taller (the adult), wider, and over twice as long makes no sense. Think about it. I'm not saying it's a risk free activity, but we are far more likely to die doing something else that we wouldn't think twice about. You've decided they're unsafe because they were relatively uncommon until recently and because many of us are no longer used to seeing anything but cars on the streets. The fact that kids used to ride their bikes on the streets all the time has been lost from collective memory since we as a society have started driving them everywhere along with ourselves.
You really don't see it? They're going to create these bike lanes by taking a car lane and walling it off. Thus, more traffic and it sucks for everyone but bike riders.
I know that a lot of bike riders think of this as a positive, which is unfortunate. You can't ride a bike unless you're physically fit, which rules out the disabled, the elderly, the young, and much of the poor. Also to people who sweat a lot, and entirely genetic problem. It's like a giant middle finger to everyone in society. The attitude seems to be, "tough, now it's time for YOU to suffer!"
How physically fit do you need to be to ride a bike? It's not that hard and the beauty is that if you're not that fit now, you can get more fit by riding.
How does it hurt the young? If they're too young to ride there are lots of options for the parents to bring them along on a bike (via trailer, bakfiets, or whatever). The young certainly can't drive.
The poor? They're too poor to ride a bike, but they can own a car, pay for fuel, and for parking? Sorry, that doesn't make sense.
It's not like the road is going away completely or there aren't going to be trains or buses for people who aren't able to ride.
Take a good look around your city and notice how much space is devoted to the automobile. If you could take even 10% of the cars away by making it practical for people to get around by other means, imagine how much space that would free up. There might even be LESS congestion in lots of places.
The goal of science is to build better mousetraps. The goal of nature is to build better mice.