Let’s say a driver drives 6 days to and from work, x 52 weeks =
312 days. And let’s say this driver drives 30km per way (e.g.,
Woodlands to town, Changi to town, Jurong to town). Thus, annually,
the driver travels 312×30 x 2 = 18720km. Thus, I would say that
annual mileage in the range 15000-18000km is reasonable, whereas
anything more than 18000km would be considered excessive.