What you want then is say, someone on minimum wage that has to travel lets say 35 miles each way to work and back because there is no work in their area or maybe a retired couple on a state pension living in a rural area and have to travel say 20 miles each way for a supermarket or doctors etc and have a small car just to keep the cost down should pay more to use the roads than say someone on £50,000 a year with a big car and only travels 10 miles a day to and from work.