Or decrease the need for cars in the first place with public transport

And road diets, and modal filters, and bike infrastructure that is wide, separated, given priority at intersections, and ubiquitous. All great ideas I fully support. But even given immense political will those will take decades to fully deliver.

Meanwhile in a country a 10th the population of America 100s of people die every year because of drivers on phones. For a measure to be effective as a preventative, people need to believe there's a high chance they will actually get caught. That's the most effective predictor. These should not be secretly installed, but accompanied with a public campaign making it clear that they are being installed and that being caught is very likely.

And people who are caught, more than just a fine, need to face a real chance of losing their licence. Not to be punitive, but because that is what they have demonstrated is necessary for genuine public safety because they are dangerous if they're allowed to drive.