How many of those journeys are ones that couldn’t be done on a bike?
The supermarket might be a mile away, but you can’t cycle back with a family of four’s shopping.
Your parents might be a mile away but you can’t take the bairns to their grandparents on a bike.
Half might be within 2km (1.6mi) but that doesn’t mean they’re cyclable.
You can cycle anywhere on a bike under 2km. I am obviously saying this in the context of segregated and safe cycle routes a la the Netherlands. This is my point, at the minute doing those small trips on a bike just doesn't seem possible to people so they drive (I am not having a go at anyone who does this, blame the system not the people). It's a sad reflection on how we've planned our transport systems. It's such a small distance, hogging around a 2 ton of metal kicking out fumes is so backwards it mental imo.
You can easily cycle back with a family of fours shopping with a cargo bike, no worries at all. If you live that close to a shop (it's a five min cycle at a slow pace) you wouldn't need to do a massive shop in one go anyway. Your alternative should be delivery by cargo bike. Sainsburys have just completed a study on cargo bike delivery and found that 98% of deliveries can be done by bike. Expect that to be rolled out en masse soon in cities.
Your kids can cycle autonomously to their grandparents place with safe routes. They do in the Netherlands. It expands the area they can play around their home as well.
I don't think many people can even comprehend a different reality to the one we're so used to which is half the problem, especially with this being a political issue at the end of the day.
And before someone says it, no, not every trip can or needs to be done by bicycle, I'm not thick. It's about enabling people to cycle short trips when they're currently driving. Reduce a good percentage of those 50% car trips under 2km and you make an enormous improvement to traffic flow, to quality of life, to air quality etc..