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Barry W

Does anyone know the status of development of diesel-electric-wired trolley buses?

The idea being that where wires are in place, the bus operates as a normal trolley bus, but also charges the battery. Off-wire, the bus as a normal hybrid bus.

The fact that it can charge up when on wires, could mean that a bigger than normal battery can be charged, extending their off-wire range. Overall, the diesel engine is used minimally throughout the total operation.

I haven't seen this type of vehicle in practice, only discussed in theory. The "light rail ready" design of the Brisbane busways (and some other cities) could allow the implementation of this type of vehicle - future installation of the catenary and power is already accommodated in the design.

Adam Parast

Barry I don't know about the status of that but Seattle had dual-mode buses like that about 10 years ago and they were an utter failure. Metro pulled out the diesel motors and is using the buses as trolley only buses now. I think because of that Metro will generally be more risk adverse than otherwise when it comes to some kind of dual-mode buses.


I think the problem here might be that they're comparing the known costs of operating an actual trolleybus network against the unknown costs of operating hypothetical hybrids up the steep hills. I recall reading a study of a trolleybus network in LA that claimed that the maintenance costs of trolleybuses plus wire would be lower than that of just diesel buses. I can't imagine that hybrids have lower maintenance costs than straight diesels, as they've got a lot more moving parts.

As for dual-mode buses, Boston currently has buses like that, as does Fribourg in Switzerland. Don't know how well they work, but they're a potential solution for route extensions. Or people just need to get over themselves about the overhead wires: overhead utilities are all over the place and are just as visually intrusive.


This issue came up in Vancouver a few years ago. It sounded as if some managers at Coast Mountain Bus Company would have abandoned the trolley network if they could have. But Vancouverites love their trolleys. One of the best improvements to the system in ages has been the introduction of scores of New Flyer articulated trolleys about a year ago.

Last year, coming into downtown from Boston Logan I was on a diesel/trolley hybrid. At some point along the way the driver gets out to put up the poles. In the opposite direction I think they retracted automatically.


Not that I expect this to be considered as a solution--it's too capital intensive, and bound to start all sorts of nasty political fights--both from those who object to the capital costs, and those who regard the technology as a harbinger of gentrification--but any comments on the merits of trolleybusses (assume fully-electric ones with limited or no ability to travel off wire) vs streetcars?

You've commented quite a bit on the mobility aspects (the busses, which can maneuver a bit, have an advantage here), and others have commented on the social aspects of the technology choice (ride comfort, cultural biases, etc). But I'm interested in:

* What is the reliability issue with trolleybusses? Trolleypoles and 2-wire systems vs pantographs and single-wire? Dewirements en route?

* Can electric streetcars (assuming modern models) be reliably expected to climb 15% grades--I have a sneaking suspicion that the answer to this one is "no"; most streetcars with which I'm familiar (which isn't many, however) max out around 9%-10%.

Eric Doherty

I wonder how strong this supposed opposition to trolley wires is? In Metro Vancouver there is often some opposition to any extension to any bus line in high income neighborhoods - usually focused on noise and crime. But the opposition usually turns out to be shallow, if the bus service is put in anyway the issue is usually quickly forgotten without much fuss.

The real problem with extending trolley wires here is that a few in the transit agency and municipalities are extremely hostile to the technology. They seem to think that wires for streetcars add class, ambiance and 'legibility'; but wires for buses are ugly and expensive.

I would also add another advantage to the list for trolley buses, the ability to have multiple drive units driving multiple axles for better snow performance. The best example of this is the 80 foot double articulated trolley buses first introduced in Zurich Switzerland.


As "anonymous" stated, the Swiss city of Fribourg has bimode busses. Actually, they now have them in the second generation, so, they seem to be happy with them. The issue with any kind of bimode bus is that they are heavier than a single mode (diesel or trolley) bus, and it is in particular the internal combustion mode performance which suffers.

All modern (articulated) trolleybusses do have an auxilliary power unit (normally a generator attached to stadard diesel motor, found in automobiles; the one used in most Swiss trolleybusses comes from Volkswagen). That gives enough power to move the bus around obstacles, or between two stops, if it is not too steep. According to the vehicle description of the Verkehrsbetriebe Zürich, the auxiliary power unit of the new Swisstrolley 3 has an electric power rating of 50kW (compared to the traction motor power rating of 2 times 160 kW (yes, these articulated trolley buses have two of their 3 axles driven).

To Wayne: Dornier has a trolley pole attachment with actuator, which allows to raise and lower the poles without the operator having to go outside of the vehicle. At the raising place, two guiding boards, about 1.5 meter long are mounted at the side of the wires. The Swiss city of Winterthur is using them in regular operation, and the Swiss city of Zürich had this system for a few years when there was serious street construction going on, and the trolley bus had to be rerouted (see also above).

to EngineerScotty: Trolley buses are considered to be at a higher line capacity than diesel busses. Most trolley busses in Switzerland are articulated, either around 18 m long with three axles and one articulation, or around 25 m long with four axles and two articulations. The few "standard" trolley busses are operated with a dedicated low-floor trailer (such as in Zug or Lausanne).

So, even on "flat" lines, the line capacity is a good 30 or more percent bigger than with diesel busses (or you can use fewer vehicles for the same transportation capacity).

Trolleybusses are also considered as a low-cost version of a streetcar. The overhead equipment is, agreed, a bit more expensive than an elastic streetcar-style catenary, but there is no need for tracks etc. But it does occasionally happen that the trolleybus line will eventually get replaced with a streetcar/light rail line; the substations are already there, and in many cases, the right of way is already reserved due to the reserved bus lane.

When it comes to reliability; it is pretty good, and derailments of the pickup shoes happen but not too often. Keep in mind that most trolley busses are not operating faster than 60 km/h.

In Switzerland, the maximum allowed grade for new lines is 7%; for short stretches, maybe up to 8%, an exemption can be received. The maximum grade I am aware of of a streetcar line is in the German city of Würzburg, where it reaches 10.5% over a short stretch. Therefore, your second question can be answered with "no". If the grade has to get higher, and you will want to be on rails, you will have to switch to a cog-railway system. In an urban environment, such a beasts exists in the German city of Stuttgart (Degerloch), which gets up to 18%.


Ever since I saw a story about the Port of LA in Wired, I wonder why I do not hear more about pursuit of fully electric vehicles. I don't see a curb weight listed, but the Balqon Mule raises some questions, especially with a large bus manufacturer only a few hours away.

Aleks Bromfield

I have to say, I've never quite understood the opposition to trolley wires. When I first visited Vancouver, it was always a relief to see the wires overhead -- a very concrete reminder that I haven't yet civilization, and that no matter how lost I was, there was a bus that could take me home. Now, in Seattle, I picked my current apartment in large part because it was right next to a trolleybus (the 44).

One thing's for sure: none of the people who are complaining have ever walked underneath an elevated train. Compared to the monstrous footprint of an el, trolleybus wires might as well not exist...

Steven Dale


Most streetcars top out at 10% gradient and lower is better. 15% would be too steep for any standard rail vehicle to ascend.


toronto ripped out their trolley buses in the early 90s in favor of the then emerging technology CNG buses which were a complete failure and they regretted it since. they have in fact recently looked at building a new ETB system.

seattle would be crazy to dismantle their system especially given the topography of the city. if anything it needs expansion.

trolley bus lines are fast and easy to install. installing streetcar lines are still quite a process, most of which is water and sewer line relocation. anyhow both modes have their place.


To Eric Doherty: Please forgive my nitpicking, but the first double articulated trolley bus in Switzerland were introduced in Genève, and it was one of those Genève busses visiting Zürich which led the VBZ (City of Zürich Transit Authority) to order 15 of those 25 m vehicles.

They do indeed have two driven axles, and theyy also have a lot in common with the normal articulated Swisstrolley 3 (such as the electric equipment, including the motors). That said, compared to the normal articulated vehicles, they are slightly underpowered (but still, with 320 kW nominal at the tyres, pretty well powered).

I also have seen double articulated diesel busses in the netherlands. I don't however have any further technical details.


The dual-mode buses in Boston actually have both automatic retraction and extension of the poles: the only problem is that they're worried about the risk of the poles coming up in the highway tunnel at 55 mph, so when the poles are lowered, they tie the pole ropes down, and untie them before raising the poles. This is done at Silver Line Way either by an employee stationed there or by the driver. As for APUs, all modern trolleybuses have some limited off-wire capability, with batteries being fairly common and used in places like San Francisco and Moscow.


Travelling in trolleybus on auxiliary diesel is horrible experience. It's ten times more noisy and shaky and it can develop only 30 km/h on flat road. Given the current progress of recent hybrid diesel-battery vehicles, I'm looking forward at trolleybuses with auxiliary batteries with ~ 10 km wireless range - enough for short extensions beyond wires.

AFAICT, the steepest streetcar tracks is this 12 % stretch of tracks in Lisbon. There used to be 12 % grade on Pittsburgh Railways that was much longer and with much harsher winters. I guess that nobody would approve such tracks these days though, maximum standard grade these days is 6 %, exceptionally 8 %, grandfathered steeper grades are eased during reconstructions if possible.

Pdfguru: At least, chassis of Citélis 18M can't accomodate motor for 2nd axle so unfortunately, there are articulated trolleybuses with single powered axle. Some of them also without auxiliary engine.

Joseph E

Here in Long Beach, California, the municipal transit agency has been replacing almost the entire fleet with diesel-electric hybrid buses. They are certainly quieter and have somewhat better acceleration than the old diesels, though any brand-new bus will be somewhat more comfortable than one that has 100,000's of miles on the suspension and drivetrain. We have few significant hills, but there does some more power.

Honestly, I did not know we had the hybrids until they repainted them to show off the battery packs. The diesel motor is still somewhat noisy and causes vibration, just at a low, constant level.

In contrast, the trolley buses in San Francisco are quiet and climb amazing hills without a hitch. You can see why they replaced most of the cable cars with electric trolley buses.

Eric Fischer

Recent San Francisco trolleybuses have battery backup (referred to as "EPU"). They don't tend to go very far or very fast on the batteries, though.

Jarrett at HumanTransit.org

Eric.  Yes, EPU is definitely just for emergencies, not for route extensions.  I recall one power outage in the late 80s that left a 1-California trolleybus (old, pre-EPU version) blocking all lanes of Stockton St and thus blocking the Stockton tunnel.  EPUs solve that sort of problem, but not much more.


I don't understand the opposition to trolley wires, either. I don't remember there being any fuss when the trolley buses in Vancovuer were extended to Canada Line Stations (I'm thinking of the #10, #3, and I think a few others that now follow Marine Drive to Cambie) Were there new wires for that extension? I'm not exactly sure.

I know they're installing new wires on Granville Street (or more accurately replacing ones taken down when construction of the Canada Line started) and it's gone really very quickly without much hassle at all.

Frankly, I have to wonder if the tendancy not to extend trolly bus lines has more to do with agency bias in Seattle than it does with NIMBYism, but I don't know. I don't follow their news.

That said, anyone who has riden the 229 bus on 29th avenue in North Vancouver will know what a wonderful thing trollybuses are when climbing hills. The first time I took it I thought we would roll backwards. Even on flats they are clean, quiet, so comfortable to ride and much less jerky and bouncy than diesel buses - I really don't understand why they're not used more often.

Jarrett at HumanTransit.org

Tessa, the trolley wire extensions on Marine Drive were not in an area with a lot of sensitive neighbours; much of the surrounding area is more or less industrial.  Doing a trolleybus network in North and West Van might eventually make some technical sense, but it would need to happen in the context of considerable densification, and that would anger whatever neighbors weren't angered by the proposed wires on their street.

Of course, streetcar advocates have the same struggle.  See, for example:  http://www.humantransit.org/2009/08/vienna-do-the-wires-ruin-it.html


Didn't SF convert at least one major route to trolleybus recently (the 31?). I don't recall any resistance (though it happened just before I lived there briefly in the 90's).

Anyway, I like them for the same reason Aleks stated above: they're a visible indication that "here lies a bus route" in much the same of course that streetcar tracks would. In that way the wires are a *useful* distraction, as opposed to the understandable nuisance of power lines which are just - everywhere.


I just noticed this is your first post on trolleybuses (as far as I can tell). It means I have a few questions: what density do you need then for trolleybuses to make sense and why is that? Would Lonsdale density work? Would there also have to be a larger enough number of routes to justify putting in all the infrastructure for the ones that do matter?

What about the justification for putting trollybuses in just for the benefit of having a zero-emissions fleet. Are there better ways to achieve that? Maybe this is looking a little bit too far in the future or outside of your area of expertise, but might that change as peak oil takes hold?

Maybe this would require a full post to sort through all the questions. I'm also interested in what other cities use trolleybuses and where they've been successful. Whenever you got the time. =)


Adam, The Bredas were converted to straight electrics after they were retired from tunnel service. The DE60LFs replaced the Bredas in the tunnel, and the converted bredas in turn replaced aging 4000 series MAN SG-T310s. Infact, there were only 46 4000 series coaches, whereas there are 59 of the converted bredas.

Aaron Priven

I think most people think overhead wires are ugly; that's why there are programs to underground utility wires, for example. In the height of the streetcar era people in DC forced the streetcar company there to use an underground trench for their electricity rather than a wire, for aesthetic reasons.

Personally I'd rather have the slight ugliness of wires than the louder noise of diesel engines, but I can understand why people might disagree.

If hydrogen fuel cell buses become a practical alternative, I wonder whether they will make trolleybuses obsolete. Hydrogen buses are quieter than diesel buses (although not so quiet as a trolley bus) and use the same kind of electric motors.

Alek F

Seattle should definitely continue using Trolleybuses, period. Please don't replace them with traditional buses (even if they're environmentally friendly). Don't make the same mistake that Los Angeles did! (yup, Los Angeles had a trolleybus system in mid-20th century, which was destroyed by the auto industry and replaced by buses. Which caused tremendous drop in ridership!)

Mike Lindblom

I expect the Seattle government will make a few proposals to string the trolleybus lines farther out, and as your story indicates, every block will be meticulously argued, just as in the monorail and Highway 519/Sodo projects. Great column...


FWIW, a few years ago, the Swiss city of Lausanne (which has grades comparable to Seattle, if not steeper) was seriously considering terminating the trolleybus operation. Despite considerable "support" from Mercedes Benz, they stayed with trolleybusses and acquired the already mentioned Swisstrolley 3 (carbody made by Hess, electrical equipment made by Kiepe).

... and there are no MB busses on the network at all...

Erik G.

Route 82 in the above map is an "Owl" or night-bus service and is operated by a diseasel.


In other words, stupid biases which case unwillingness to make capital improvements on public transportation routes causes it to be hard to extend trolleybuses -- despite the fact that hanging wire is really pretty cheap, compared to laying rail.

Why, these are very similar to the reasons it's hard to extend rail lines. Except that rail lines have more political support for whatever irrational reason.

Practically, trolleybuses vs. streetcars -- junction work can be a real mess for trolleybuses, so if you're planning a large intersecting spaghetti network streetcars may make your life easier. ('emergency batteries', however, may eliminate this by allowing for buses to simply drive through unwired intersections.) Streetcars provide somewhat better ride and significantly more accurate station "spotting". But trolleybuses are pretty darn nice.

They should just string the wire for the northern extensions of the 1 & 2.

Ian F

The situation for extensions in Vancouver is also made more challenging by the City's policy against new above-ground electrical distribution wires, including the type used to deliver power from substations to the trolley overhead. (These are the two large black cables typically seen running along the street-side poles on Vancouver trolley routes.) A special exemption from this policy was required for the extension of wires along Marine Drive and the policy was also a potential threat to a proposed extension along Renfrew St, between Hastings and McGill.

Historically, the extension to UBC (through a bucolic golf course and forest) was vigorously opposed by some, including a provincial politician and UBC professor. Ironically, this individual was also promoting a floating bridge to Vancouver Island, including a freeway up roughly 40 km of the pristine Gulf Islands. Now which would be more blighting???

Now back to Seattle, the route density on Queen Anne hill is incredible, it is only 700 m from the route 1 to the 13. I recall there is also non-revenue wire tying together all the routes. So, if an extension weren't deemed feasible, it would be simple matter to extend the 1 or 2 to Seattle Pacific University using the wire for the 13. Extension to Ballard would be better still from a network perspective, but likely not strong in ridership potential.

The outlook in Seattle is indeed worrying and further illustrated by the routine weekend diesel operation of many trolley routes, though at least one can credit KC Metro with providing "explanations" for this on their web page.


What is the basis for the Vancouver policy against overhead wires--cosmetic, or safety? In the Pacific Northwest (an unfortunate UC-centric term which tends to include the SW of Canada along with Oregon and Washington), the combination of tall evergreen trees (which generally have shallow root structures), frequent rain, and occasional high winds aggravates the safety issues with overhead electrification--trees fall on power lines a LOT here. (In a big windstorm, the damage to the electrical system is frequently severe). While the safety risk posed by a 600-750VDC catenary system is minimal (the voltages themselves are lethal should you complete the circuit between the supply and ground), this voltage isn't high enough to pose electrocution risks for persons standing on the ground nearby from voltage gradients between the feet--a major concern with multi-kilivolt (or more) power lines.

Here's one area, of course, where electric rail has an advantage over electric busses--one-wire catenary systems are generally safer than the two-wire systems that trolleybusses require.


Above should read "US-centric".... dang fat fingers. :)

Jarrett at HumanTransit.org

Scotty.  I suspect if falling tree-parts were such a huge issue, you wouldn't see trolleybuses in rainforest cities like Seattle and Vancouver -- nor in Wellington, NZ, one of the windiest cities in the world.  Trolley wire is much stronger than it looks, and even large falling branches often don't damage it.  You just send someone out to cut the branch down, and you're on your way.


Why is electric trolly bus maintenance now such an issue in Seattle? I recall the old jerky electric bus's in Seattle were on the streets for about 40 years, 1935 to 1975 approximately. They lasted much longer than their noisy, polluting, petrol sucking cousins.


Correction on when the electric bus started service in Seattle: it was 1940. Read a great history of the electric trolly bus in Seattle at http://www.mehva.org/60years.html


It's not the branches; its' the entire trees that fall down. Given that most electric transit lines are in urbanized areas, treefalls are less of an issue--but it's still a big problem for the greater power grid.


When Metro runs diesel buses on the trolley routes during weekends on Capital Hill it is hell. The diesel buses are so loud especially on Bellevue Ave which is like a canyon with the apartment buildings lining each side of the street. The noise alone is reason enough to say no way to diesel buses replacing the trolleys!

Joel N. Weber II

How far are the Proterra BE-35 and BYD eBUS-12 from being able to replace trolleybuses without the challenge of stringing overhead wires?

Richard C. DeArmond

The principle reason that Seattle got rid of dual mode buses in the tunnel is that Sound Transit was planning build a light rail line through the tunnel, and they were afraid that there would be major trouble with dual-mode trolleys having the poles dewire and make contact with the 1,500 v. overhead for the light rail. This is very undesirable. I would like to have seen them try harder to prevent such contact, but they chose not to do so. Seattle is planning to buy a new fleet of trolleys (rigid and articulated) to replace the current ones. They will have off-wire capability, but I do not know how far they will be able to travel off-wire. More interesting is the plan to try out two more trolleys that will have a 30 mile off-wire capacity. If successful, they would like to buy 200 such vehicles to supplement the current ones. They would be able to use the current overhead to feed the batteries. This way a bus can stay in constant use during its run and not be sidelined at a charging station. Saves money. Ultimately, the entire system could be trolley/trolley-battery dual mode. A great idea. Hope it works.

R. W. Rynerson

Having worked as a service planner in a trolley coach system, I can testify that the flip side of having a capital project for route extensions is that it sobers up the "take it out of recovery" or "just deviate a few trips a day" politics that dominate U.S. and sometimes Canadian transit planning.

As for "maintenance costs" there is a report from Seattle back in the 1960's that unveils most of the fallacies in comparing Diesel bus costs with trolley coaches. These fallacies have been used by opponents of trolley coaches, most recently in Edmonton. The report was by the Washington Society of Professional Engineers, as I recall.

For more on the interaction between service planning and trolley infrastructure, read:


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