The Lake District is the busiest National Park in the UK, unfortunately, the few car parks are very expensive and often full from early on in the day. One initiative to combat this is a free bus service from Ravenglass to Wasdale Head which will be of interest to SOTA activators who may be attempting activations on Scafell Pike G/LD-001, Great Gable G/LD-005 and Pillar G/LD-006, plus a few other SOTA summits. It is a shame that other areas such as Snowdonia are not tackling excessive visitor numbers in the same way!
Public transport in snowdonia is far superior to the lake district, especially if you compare with the western lakes.
All of the main trailheads for snowdon are served by regular bus routes.
Even the eastern lakes have problems: try getting to Tebay by public transport (despite have excellent rail and road passing through, it is served by a twice weekly bus service only). Similar for Sedbergh.
Personally, I would prohibit road use by motor vehicles beyond the western end of Wastwater, turning the road into a 4x4 track (as in Ennerdale)
One thing Cumbria does get right with regards public transport, is the availble county map of all routes at