Relevant thread:
Thanks. From that thread I learned:
- In Melbourne, tram switches can be operated by the driver from within the cab using buttons.
- This appears to be unusual as switches are generally centrally controlled
- Nobody referenced a system that didn’t use track switches
This is all good information, and none of it is surprising, so frankly I’m disappointed. I was hoping there were systems that somehow the trolley itself could steer one way or the other without track movement being involved and I was eager to learn how they worked.
But I did not know that track switches were ever controlled by the driver, so I am definitely glad to have learned that. In the context of the thread I’m sad they use buttons and not a giant steering wheel.
Below is a link to a bit more info specifically about the streetcar switching system in Toronto, which is typical except for the non-standard track gauge (which my understanding was originally so that the wheels of horse-drawn carriages with standard axles could ride in the “ruts” on the inside of each rail; later, when the subway was built, it used the same non-standard gauge for compatibility in the event that streetcars ever used the same tracks, which never happened).
I think the notion that a streetcar might be able to “steer” its way onto one track or another at a junction probably comes from the fact that streetcar track switches are not as obvious as train track switches because everything has to be flush with the surface of the road. But I don’t see any practical way this could work; even if you could “steer” the front truck wheels, what about the rear truck? Or how about if there are two or three streetcars coupled together?
Switching is the only way it can work. I believe the Toronto system has three kinds of switches. Rarely used switches are fully manual and have to be moved with a crowbar-like device. Others are electrically operated by a button in the streetcar. Still others are automatic and can be set and reset with transponders at the front of the car and at the rear of either the same car or the rear of the last car in a coupled train set. I don’t believe there’s any central control of the switches except in the sense of central control of a route which presets what the transponders are supposed to do.
Below the link is a pic of a streetcar driver operating a manual switch.
Here’s a good photo of old single-point switches, installed brand new in 1932 (there’s a download original button at the top left to see the full size version). In this case only the left rails have the switch. I assume the way the rail on the right bulges out that little bit of a rail inserted is a reinforced and/or replaceable piece because that’s where a turning car’s wheel would “drop” off the rail and tend to mash it up over time.
There’s also spring switches, which were common on single-track streetcar lines and electric interurbans at passing sidings and terminal loops. They would be “set” for a particular direction in a facing-point movement (usually straight through or to keep right) but either way, a car coming from the opposite direction for a trailing-point movement would just push the rail point out of the way and it would snap back into position after the wheels passed. In a one-way to one-way junction with only trailing movements, it looks like perhaps it’s not even a switch so much as just a moveable block that the wheels push into place depending on which track the car is on. Maybe that’s still a spring switch, it’s hard to tell. Also that track is in awful condition.
I’ve never heard of any streetcar (or subway) having direct mechanical selection of route like a bus or car has.
Besides switches thrown by standing next to them and moving a lever, there have been various electronic ways invented to communicate a route selection to automated switches. Easiest is one used some places on the Chicago L where an override is only occasionally needed: the operator pulls up next to a wayside pole where he just reaches out the window and pushes a button that changes the track switch. In the late 1940s, Chicago (and probably other rapid transit systems) used a coil that functioned as an identity token, attached to the front car of the train to trigger switches at junctions. Later, more sophisticated electronic ways were developed whereby the operator could press a button in the cab and introduce a low-voltage signal into the track that would move the track switch, and such systems are now probably most common worldwide for both tram and metro operations.
One interesting technique I saw used in the early 1980s by San Francisco streetcars and light rail vehicles involved small dot markings on the pavement between the rails and a wayside signal that changed every 30 seconds to indicate one routing or the other. The motorman would pull up to marking 1, wait for the signal to show the direction desired, then pull forward to a second mark. That put the vehicle over an induction loop (as often used to trigger traffic lights) and told the electronics to throw the track switch to the selected route. I don’t know what this technique was called in the industry, nor whether it’s still in use.
Wow, thanks. I learned more things today. Streetcars are cool.