Bear with me...
Say you employed a nanny who drove her own car and you paid mileage. Nanny had a decent car when interviewed, big enough for three kids, school bags, buggy and all the associated gubbins.
A year later, nanny started driving a not so good car due to not being able to afford repairs on decent car. Smaller, older, possibly not as sturdy.
Would this make you in any way question the nanny's ability to do her job if it involved quite a lengthy school run?