Why are these vehicles selected for they routes? Is there reason behind it or is it just random.
In terms of Hybrid buses, a batch would tend to be based on a particular route, tend to but not always! This would allow their full economic capabilities to be utilised and understood
A couple routes
need to be single deckers so this cant be helped. The 30 and 38 come to mind. Others, in normal times are single decker due to customer numbers. The new B8's were ordered for the 30, but will operate on other routes often.
Generally the main reason behind a batch of vehicles being allocated to a route is as said, they are bought in batches and as such a batch can be bought to suit the
PVR (peak vehicle requirement) of a route. For example; 30 B5TL's were bought for the 26 - the 26 requires 30 buses, in the peak.
As part of wider orders, where large batches of vehicles are ordered, a couple of routes will be selected.
Over time, when more new buses are bought, others are cascaded through the fleet, meaning they end up on other routes.
Generally, but not always, batches are kept together.\
But even in
normal times, buses bought for routes aren't generally restricted to those routes and often work on others regularly, even the 26 batch wanders.
Hope this goes some way to help you understand?