The way I see it is no one should run under. Scratch is essentially the perfect day as far as ups is concerned.
Not exactly according to Industrial Engineers inside and outside UPS.
The allowances are developed with the belief that they provide +/- 5% correct planned time allowances for 95% of the drivers 95% of the time.
So, with 20 drivers on any normal day, 19 of the planned allowances should be correct to within +/- 5%.
19 of every 20 drivers, on average, should expect that 1 day out of 20 that his/her planned day is outside of the +/- 5% parameters.
1 out of 20 drivers can expect that their planned day is outside the +/- 5% parameter.
The allowances are based on a steady work pace, using good work methods with
perfect knowledge of their area. Included in that allowance is about 15% to account for unforeseen issues, tiredness, and a percent of problem packages.
Perfect knowledge of their area is knowing where every stop is, where at that location to deliver and name of consignee at business stops, etc. It also assumes the driver is aware of and plans for closed roads, washed out bridges, etc.