Why would a city opt for trams instead of trolleybuses for public transport?

[ӔO]

I'm just wondering why one would use trams over trolleybuses inside the city when the advantage is clearly in favour of trolleybuses.

Considering the case of the TTC, which only has partial sections where the trams/streetcars run on their own dedicated lanes. The vast majority of the network runs on 4 lane wide, 2-lanes each way roads, many with on street parking. TTC did have trolleybuses before, but they were withdrawn in favour of diesel buses.

The trolleybus:
- is just as clean as the tram
- does not require expensive and time consuming tracks to be installed on the street.
- can manoeuvrer around obstacles, like accidents or broken down trolleybuses. Unlike the tram, which will get stuck behind anything that breaks down on the tracks.
- can use both lanes on a 4 lane road, unlike the tram.
- can stop on the outer lane to unload and pickup passengers, and let cars pass while it is stopped. Unlike the tram, which will stop both lanes to unload and pickup passengers.

The only disadvantage I can see is that it it's twice as likely to drop it's power rods off the overhead wires, compared to a tram.

What good reasons would there be? This has been bugging me for at least 2 months.

[EnternalD]

Well you are wrong if you say that trolleybus is twice as like to drop his wires , it is closer to four or six times.
If tram uses pantograph this is nearly impossible. Even more pantograph saves huge amount of wire maintenance in no need of using frog devices.
Tram could really have higher capacity in line.
If city is located in mountainous terrain tram has really edge over trolleybuses, but not as high as compared to buses.
Metal to metal traction, and higher power engines of tram should provide energy savings, but in reality this is rarely considered, because these electrical networks are still cheaper than buses provided that enough passenger ride them.
Flexibility is greatest problem in tram transport. If there are enough passengers probably metro is even better variant.

[paco_m]

The benefit of the tracks (and the trams) is that you can add trailers without the problem that they might pull out in the curves so you can turn around closer curves and at a higher speed than street vehicles of the same length can. In other words trams can be larger/longer and transport more passengers.

- can manoeuvrer around obstacles, like accidents or broken down trolleybuses.

I still remember the last time when a trolleybus tried to overtake another trolleybus
They obviously crashed with their current collectors and all the electric cables came down over the cars,
a really dangerous situation for everybody there and the whole street was closed for two days...

[inkelyad]

Tram don't need street. Best way is to build 2-lane street + tram tracks. Not 4 lane street. It is much cheaper.
Tram is faster.
And tram itself have very-very long life.

[Lmallet]

There is a good article on why Toronto stopped using trolleybuses here:

http://transit.toronto.on.ca/trolleybus/9003.shtml

[EnternalD]

The benefit of the tracks (and the trams) is that you can add trailers without the problem that they might pull out in the curves so you can turn around closer curves and at a higher speed than street vehicles of the same length can. In other words trams can be larger/longer and transport more passengers.
I still remember the last time when a trolleybus tried to overtake another trolleybus
They obviously crashed with their current collectors and all the electric cables came down over the cars,
a really dangerous situation for everybody there and the whole street was closed for two days...

Well I had never experienced such a sighting despite the fact I am riding the trolleybuses every day at least last few years. Well at least where I live trolley wire columns are really close enough to prevent such disasters (only little wire drop is possible). Overtaking with trolley other trolley is really rare practice, and if needed in some high capacity streets there are already second line of wires nearby. Also not all trolleys are equipped with offline capability (and those who have it it is only indented for easier parking). If need arises there are few mobile trucks, with some equipment to fix trolley, and has lifter on top to reach the wires. there is mobile workyard fitted in bus too.

[sdog]

toronto has the room to easily give trams their own right of way. to me as a foreigner here it looks like they're not doing it (in fact try to slow down the tram artificially*) for ideologic reasons.

With rapid bus systems you quickly get to capacity limits. The absolute upper limit, using all new tech available right now (low floor triple articulated etc) should be 40k 1/h. Trolleybuses won't increase this much. For higher capacities you need rail and their own right of way.

Another advantage, two directional tram track needs less room than two directional trolley bus lanes.

Right now Toronto has 11 km/h average speed on it's most heavily used King st line. During rush hour the lane with rails is reserved for streetcars, and buses, ... and taxis,  ..... and cars turning left and stopping everything for ages. Exclusive use of it's lane, own signaling with priority before left turning traffic

Congestion can still be prevented since Automobile users will just avoid those streets if they're so disadvantaged there. A second step could be generally prohibiting left turns on those roads. Toronto has a dense grid, very easy to get into the desired direction via a parallel street.

(could be a good general rule , no left turns in gridded downtowns, turn right 3 times. Should let the traffic flow much better, those left turners take up at least one third of most crossroads capacity.)

[paco_m]

Overtaking with trolley other trolley is really rare practice,

It was an accident, first day of a driver that only worked with diesel buses before and seems that he forgot that there is some difference with the trolley...

[Fabio]

(could be a good general rule , no left turns in gridded downtowns, turn right 3 times. Should let the traffic flow much better, those left turners take up at least one third of most crossroads capacity.)

I never thought of something like this, but it's a genial idea!

Another one would be making parallel roads one way in opposite direction.