Bristol Cycling did an article on this a while back, resulting in an often-shared infographic with the headline that each taxpayer in the UK (driver or not) pays a road transport subsidy of £2,500. That article is a few years old now and some references appear to be out of date, so I did my own research.
That headline figure seems a reasonable headline approximation, though it does depend on how you account for a range in estimated costs. I’ve come up with figures between roughly £1,400 to £3,000 – but in all cases, the costs from climate change are not included. These will likely increase that figure further.
My data can be seen here:
If you want the spreadsheet from which these screenshots are taken, you can download it here (XLSX).