We’re sitting at Third and Seneca northbound on the 3, a trolley bus. The passenger in front asks me what my favorite routes are.

“I really love doing the trolleys,” I respond.
“Oh. I’ve never been on one of those,” he says. I point out that he’s sitting on one as we speak.

There may be more than one person out there who’s not entirely sure what a trolley is, or who has perhaps never ridden one. In the interest of sharing my passion for them, and in particular enlightening our far-flung readers, I’m compelled to offer some information on what exactly trolleys are, and why they’re so great.

A trolley (or trolley bus, trolley coach, or trackless trolley) is a bus powered by connection to overhead wires. Poles extend from above the coach, connecting the bus to its power source. You’re familiar with streetcars and light rail, which only need one overhead wire. Why does a trolley need two? Because with rail the electrical circuit is completed by the metal rails upon which the vehicle travels. Trolley buses, with their rubber tires, have no such metal contact point on the ground and thus need two wires to complete the circuit- one a live wire, the other a grounding (dead) wire. The grounding wire is usually the one closest to the sidewalk.

Picture 2

A trolley does not contain an engine or transmission, in the traditional senses of those words; there is simply a series of circuit boards inside the coach which direct power to a single gear. The “gas pedal,” called a power pedal, is less like a gas pedal than a rheostat. Like a dimmer on a light bulb, you press it to adjust the amount of current being poured into the gear connecting to the rear axle. If you floor it, you’re dumping 750 volts into the rear wheels, and you can fly up the steepest hill in the network– that would be the Queen Anne counterbalance, at 18.5 degrees– without a hitch (James Street is a close second, at 18.3 degrees. Why does the bus go so slowly down these hills? Simply for safety. Trolleys and diesels have a speed limit of 10mph downhill on these segments, to avoid plunging into Puget Sound. Buses weigh at least 30,000 pounds, after all!).

Trolleys, like public transportation in general, are much more popular outside the US. Only six cities in North America have a trolley system. In order of size, they are: Vancouver, B.C., Frisco, Seattle, Dayton, Philly, and a couple lines in Boston. Hilly cities benefit most from a trolley network. A trolley’s torque is dramatically stronger than any conventional diesel engine, and thus they can handle hills much more easily. You’re not shifting gears with an internal combustion engine, waiting around to get up speed– rather, you’re just shoving current into that single gear, already flying. The agility with which they can take the hills is pretty astonishing, given how accustomed we are to large things in general always moving slowly. It’s also worth pointing out that the added torque and better braking lend themselves to superior performance on flat stretches as well.

Why are trolley bus brakes better? Trucks and diesel buses are equipped with engine retarders, which slow down the engine when you’re coasting, so the regular air brake, called a service brake, doesn’t have to do all the work of stopping such a huge vehicle. Trolley buses have “Dynamic Brakes,” which are a step up from retarders; they perform the same end function, but rather than slowing down the engine, they actually reverse the thrust of the motor. The generator circuits of the traction motor are loaded down with electrical resistance, resisting the rotation of the generators and thereby slowing down the rotation of the wheels. Reverse thrusters are used to slow down airplanes. Is that better than a normal engine retarder and service brake? Abso-friggin-lutely. It also minimizes wear on friction-based braking elements, allowing the service brakes to last longer.



The poles above the bus are spring-loaded and push up against the overhead using springs and air pressure. A small U-shaped shoe with a carbon contact surface (“carbon insert”) is what actually touches the wire. The U-shaped shoe pushes up against the wire, which sits inside the ‘U.’ Electrical current comes from a network of power plants stationed around the city. These are separate from the city’s electrical grid– regular power outages don’t affect the service. In the old days the poles were made of steel, as seen below, and they flew off all the time. Now they’re made of fiberglass, and can stay on the wire with greater flexibility.


Below, you’ll notice the slight bend of the white Keipe Elektrik poles currently in use (two coaches, 4110 and 4236, mysteriously appear to still have steel poles; those two are harder to keep on the wire).
Picture 14
The length of the poles and ropes behind the coach give you twelve feet of leeway on either side of the wire to maneuver around traffic. Twelve feet is the width of a regular lane, which means you generally have two lanes to work with, but if the wire is carefully positioned, sometimes you can straddle three lanes if you go slowly. Madison between 8th & 5th and 5th Ave North at Republican are examples of this.

You might notice drivers staring intently through their mirror at the back window– they’re looking at the ropes outside, trying to get a sense of where the poles are above the coach. If the two ropes are vertical, then you’re directly beneath of the wire, of course. When they start slanting, you’re drifting away.
Picture 20 copy
When the ropes look like they’re about to touch in the corner of the back window, that’s as far out as you can go. The new trolley buses, arriving in 2015, will not have back windows (unheard of with trolleys), and this will make driving them quite a bit more challenging.
 Picture 17
What happens when you go too far out from under the wire? The poles pop off. Nothing holds them onto the wire except air pressure. It’s amazing to me that they don’t pop off all the time, after every bump or turn in the road. A fellow named Max Schiemann developed all this in 1901, and he was one smart cookie. The reason there are ropes connecting the tips of the poles to the back of the coach is twofold: firstly, that way you can actually move the poles about without climbing on top of the coach. Secondly, the ropes supply tension. They are spring-loaded as well, and pull downward, although with only a fraction of the upward pressure the poles possess. This counterbalancing downward pull allows for the minimization of the effects of dips and potholes in the road– things that might otherwise throw the poles off. If one of your poles is coming off too often, you might go out and redo the tension on your ropes, which involves pulling out all the rope and re-winding it around the spring-loaded wheels on the back of the bus.
Ever wondered what the phrase above, printed on the back of every trolley coach, means? Sadly it’s not a reference to tap dancing. They’re talking about a scenario where you’re wanting to inspect the shoes on top of the pole, because perhaps the pole(s) are coming off even though you’re driving properly. They’re suggesting that you turn the bus off, and then tap the poles together to discharge any spare electric buildup before getting in close proximity to the shoe. All great ideas, though the likelihood of there being any spare charge in the pole is very small once you turn off the coach.
When the poles come off, there is no backup system for moving the vehicle. There is no emergency engine. You’d better hope there’s wire your poles can reach, or a slope in the roadway for using gravity to drift back under the wire. Usually there is, but the margin for error is tiny. I find this just fantastic. It’s totally exhilarating. It forces me to be in the present, and to concentrate. Sometimes on flat ground with no live wire overhead you’ll be at a loss for what to do. The temptation is to simply push the bus a few inches and get back on live wire. A 60-foot Breda trolley is heavy, but trolleys are built to roll… is it possible to push a 55,000 vehicle with your bare hands? I won’t tell you if I’ve done so. I’ll simply say that I “haven’t,” since that would of course be breaking the rules!
Picture 24
That’s part one. Part two is nigh!

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Nathan Vass is an artist, filmmaker, photographer, and author by day, and a Metro bus driver by night, where his community-building work has been showcased on TED, NPR, The Seattle Times, KING 5 and landed him a spot on Seattle Magazine’s 2018 list of the 35 Most Influential People in Seattle. He has shown in over forty photography shows is also the director of nine films, six of which have shown at festivals, and one of which premiered at Henry Art Gallery. His book, The Lines That Make Us, is a Seattle bestseller and 2019 WA State Book Awards finalist.


  1. Thanks for fine educational information in this piece!

    As an addition, I understand that some newer trolley buses available on the market have big batteries and can run for five miles off-wire. King County Metro in Seattle is buying some of them: http://www.newflyer.com/index/2013_08_02_king_county_award

    Also there is a new kind of battery-powered electric bus in Switzerland that runs without wires and recharges itself via occasional rapid charging with a quick connect-disconnect device that operates for 15 seconds at selected bus stops. http://www.cnet.com/news/battery-topped-electric-buses-flash-charge-in-15-seconds/

    In Utah there is a wireless electric bus that recharges its batteries inductively with a no-contact electric pad used for a period of minutes while the coach is parked above it between runs. http://www.wired.com/2013/10/utah-ev-bus/

    I’ve heard that an issue with overhead wires for powering a bus is the maintenance cost. There is wear and tear from ongoing physical contact with the wires.

    • That’s what the 60-foot Breda busses originally were, actually. They operated electric in the tunnel via the trolley wire, and then switched to diesel once they left. They were notorious for being unreliable, something that has persisted since the diesel engines were removed and the busses made electric-only. The extra equipment made them extremely heavy as well. I’ve heard Metro needed permission from WSDOT to run them on highways because they exceeded the weight limits.

      Trolley busses can also have an Auxiliary Power Unit to allow them to move if they throw their poles or loose power. Most busses use batteries now (including the new fleet Metro is procuring), but I know the trolleys in Dayton use diesel APUs – basically making them an early series hybrid of sorts.

    • For a period of about 15 years after the opening of the Seattle downtown bus tunnel, King County Metro Transit operated a fleet of 236 Breda buses that switched between electric trolley operation in the tunnel and diesel operation on the streets of the region. They were removed from service when the tunnel was closed in 2005 by Sound Transit contractors to convert to joint operations with light rail and buses, which began in 2009. The tunnel catenary was configured for light rail, and upon reopening the tunnel in 2007, only non-catenary buses were allowed in it. The technology used for the buses in this tunnel now is diesel-electric hybrid. The diesel engine of such a bus is running between stops in the tunnel, but it turns off when the bus halts at station stops. I presume that the carbon monoxide levels in the tunnel are considered manageable even with the internal combustion engine operation that was one motivation for the Breda trolley buses prior to tunnel conversion. Some 59 of the former dual-powered Breda buses have lived on in daily operations as pure electric trolleys on surface streets, the diesel power plant having been removed by Metro technicians. http://en.wikipedia.org/wiki/Trolleybuses_in_Seattle

  2. Great article! Trolley busses are one of the more interesting features of Seattle’s bus network, and it’s interesting to hear a bit of “behind the scenes”. One of the things I’ve always wondered is why the 40′ coaches are so much quieter than the 60′ coaches; the latter seem to run their air compressors constantly. Another odd thing about the 60′ coaches is starting from stops on relatively steep hills; every now and again, the coach will lunge back and forth somewhat violently before getting going. Is that related to sticking brakes, or maybe something related to suspension of the drive wheels?

    • From what I know, it’s actually the hill-hold feature sticking. It’s really easy for a trolley to roll downhill when it’s stopped, so they have a hill hold button an operator can press that keeps a little current flowing to the traction motors, preventing the backwards roll.

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