Anyways, here we go, yo...
“Why do some buses turn around mid run?”
There can be several reasons why buses turn around mid-run. An important first point to make is that there are motor coaches (diesel buses) and trolley coaches (buses on wires). Motor coaches very rarely – if ever – switch back or turn around mid-run. For the most part, motor coaches will go to the end of the line and then deadhead to a specific point as instructed by Central if they’re behind and need to get back on schedule, or to pull into the barn. Some motor coaches during commute hours are pulling in or out of the barn and are instructed to do a portion of a different buses’ busy route on the way to the start point of their actual route. Of course, if there are mechanical problems the motor coach may deadhead back to the barn from any point in the run.
Since they’re on wires, trolley coaches are like trains – they’re essentially on an electric overhead track and must follow the pattern of the wires to get anywhere. Some of the newer trolleys can go off the wires in order to turn around or go off-route at need, but when they do this they are only capable of traveling a short distance at a very slow speed. The reason trolleys turn around mid-route is there are only a few spots where the wires enable turning. If the buses are stacked up, or a given bus is behind schedule, they must use one of these designated spots to turn around because there are of necessity no short-cuts and obviously trolleys cannot pass each other – they’d have to de-wire to do so, and we all know what a pain that is! Since the trolleys have to stay on the wire, when a trolley needs to pull into the barn for whatever reason, unlike motor coaches they don’t deadhead back to a particular spot. Instead they continue taking on passengers up until the point that they can use the wires to turn off-route and get back to the barn. This means that the bus only serves part of its usual route. A good example would be the 14-Mission: if the bus is scheduled to pull into the barn but is currently in-service at, say, top of the hill Daly City, the driver will continue to pick up passengers until the turn-off point around 26th & Mission and won’t finish the route all the way to downtown. By the same token, trolleys pulling out from the barn may begin the run mid-route. Good drivers – or maybe I should say drivers who possess simple courtesy skills – will notify passengers at the time of boarding if the bus isn’t going to complete the route. As I’m sure many of you know, bad drivers just throw your ass off without any explanation.