You have calculated against “experience”? Seems to me that would be the number one factor. I am seeing it elsewhere with unemployment so low.
While experience is a factor, it is probably not a factor in the way you imagine. In the driver population we are looking at the outlier young ages are about 35 with most ages centered around 45 to 50. The years of experience in this job is typically 10 years.
However, we get a lot of voluntary transfers so a technician may only have a couple of years in a given area.
Worse, the job tends to gravitate work tickets the new areas of construction. So, even if a driver has 10 years of experience, that driver will spend a great deal of time in new and constantly changing situations.
As such miles driven is a lousy proxy. What is needed is some sort of metric that includes time driven, (a great deal of time for technicians in metro areas is spent starting stopping, patrolling slowly down right of ways and stuck in traffic. Rural technicians handle less tickets but drive faster and further between tickets and have many less crash opportunities per day.
However, even this is confounding as many areas that were rural 10 years ago are now metropolitan.
However, right now the low hanging fruit seems to be poor training regimen and would be the easiest answer. On the other hand, a large and intense training program for a few thousand technicians can run into millions of dollar per year. Of course one technician severely injured per year can be just as expensive.
Cheers
Qazulight