If road pricing is introduced, would it be a good idea to allow a basic free milage to all road users?

It seems to me that if road pricing is introduced, (I hope not) it would be unfair on the "less well off" and would lead to a "rich only" culture of road users. By allowing a basic free personal milage to everyone (Say 30 miles per day) we could at least get to work free. Business milage would need to be dealt with under the company car taxation rules. If it works right, we would all be deterred from using cars just for leisure trips.