No 'require' in the policy. Just 'encouraged'.
Surely the cost to public purse should be the primary concern.
It does also raise the issue of bus fares not being competitive enough to get people out of their cars.
Once someone has a car, the marginal cost of running it is likely to be cheaper than the cost of public transport. If you add the fixed annual overheads (tax, insurance, MOT) and other costs (depreciation, servicing, etc), I suspect the cost differential per mile would look different. Also, car parking is often a considerable cost these days, though maybe not in Taunton.
The reality is that once you have a car, the convenience and comfort over an infrequent bus which may or may not take you exactly where you want to go is often compelling.