Pegasus is a Canadian computer program designed to work out optimum deliveries per postman in the time allowed. However, it does not take into account steps, local obstacles (wheely bins, toys in the way), time taken for people to answer the door if needed, and - the biggest and most stupidest thing of all - that a constant pace can be obtained. Like any job, we slow up the more we do, and it is a physically tiring job.
Also, automatic sorting machines are all very well, except that the accuracy leaves a lot to be desired.