can only see car use increasing tbh. Car usage almost back to pre COVID levels plus there seems to be huge demand lately for used vehicles.
Although conversely a significant drop in new cars being purchased in September, the two well may be linked (i.e. fewer new cars meaning more pressure for second hand cars and/or people keeping hold of cars for longer, therefore restricting the availability of second hand cars).
Although I would expect that there will be some who are currently avoiding public transport and are driving. However that might be at an extra cost which they might not be able to sustain long term and/or there might be other priorities in normal circumstances (such as traveling abroad, more socialising, activities for the kids, etc.) which aren't happening so can fund the extra for the car.
Either way of we are going to see an uplift in car use due to people avoiding public transport when things return to there being more people going into work (and there's still been significant numbers who haven't been back or only for limited purposes) then the roads could well grind to a halt rather rapidly.
Those days (term time) when traffic appears light compared to those days where it takes forever (as long as it's not due to a motorway being closed or the like) the change in traffic levels is about 2%, therefore even a small increase can significantly impact journey times.
As such, as things return towards normal there's likely to be a shift back towards public transport, if for no other reason than the roads might struggle to cope.