Stan as usual has excellent ideas. I just though I'd add a few lessons learned having implement several trolley scenes on my layout. I have two bump and go scenes and one dog bone scene all on Super Streets. One scene is an automated 4 way stop complete with traffic lights. Another is a taxi scene complete with taxi cueing running 4 taxis. The one I'm working on now is a simple back and forth with a bump and go similar to subject to this thread. My plan is to use a solution similar to that of Stan's described above. I want to pause my trolley at a school mid route. Here are some things I am considering:
1) I found my bump and go scenes a little boring with the same reputation each cycle. The continuous bumping operation is also noisy/distracting. To mix it up a little, I'm planning on using a timer similar to Stan's recommendation that shuts off power to an insulated section for lets say 20 seconds every couple of minutes. The timer runs continuously and has no trigger. I haven't decided on the exact timer settings. The idea is to provide a degree of randomness to the automation. Relay contacts provide track isolation and active school crossing warnings.
2) I found it nice to have an on/off switch for the automation. Then you have 2 ways to run your bump and go.
3) The speed you run the trolley at needs consideration. In my case, I was always like running the trolley at minimum speed. MTH trolleys have better low speed operation then Lionel in my experience.
4) Even at the lowest speed, trolley's progress over a considerable distance in a short time. When I figured this all out, I was dealing in milliseconds, not seconds.
5) Also, the MTH and Lionel trolleys are different lengths which for my automations was a consideration.
6) For folks using Super Streets, I found that Taxi wheel base was an issue. The Super Street taxi wheel base is shorter which introduced a couple of issues which required resolution.
7) My taxi scene uses 4 taxis. I found the automation was speed sensitive. Three of the taxis ran at the same speed. The forth taxi ran faster. I slowed this taxi to match the others by inserting series diodes in the taxi.