Category Archives: Tech Talk

Huh? What’s an “all-electric” hybrid?

Now on the streets—you might find yourself aboard one of our newest all-electric hybrids! This next-generation of hybrids is designed to be our most efficient for fuel and emissions.

Thanks to a $2.5 million federal grant, we were able to purchase four of these buses, which are similar to a Toyota Prius—just a smidge bigger. Here’s how they work: a diesel engine powers a generator, which starts the bus and electrifies the energy storage system. The electric-traction motor then turns the wheels.

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It’s a hybrid—but electric!

“All-electric hybrid” may sound contradictory. These hybrids, though, are different and have even more awesome features than the last four we launched into service in 2012.

Everything on them can be electrically powered 100 percent—and for up to two miles! (Our older hybrids can’t do this because the diesel engine powers the hydraulic steering and air compressor.) If there’s not enough energy stored in the battery, the generator starts and uses the diesel engine, which also recharges the battery.

Another cool feature is what’s called Stop/Start Drive. As the bus slows to about 8 mph—and as long as the lithium-ion battery has enough juice—the engine shuts off and the battery takes over.

During shut-off, the bus’ accessories—such as the lights, air compressor, hydraulic steering and air conditioning—are battery-powered. As the bus leaves a stop and moves faster than 10 mph, the engine starts again.


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These buses use regenerative braking, too. This means when the brakes are applied, kinetic energy is captured and can be used immediately or stored in the battery for later use. The batteries also provide acceleration power.

Good gas mileage, low emissions

We won’t know until they’ve been in service for a while, but we expect these new hybrids to get at least 6 miles per gallon … just like our other four hybrids. In comparison, our newer fleet of standard buses get between 4.5 and 5 miles per gallon. In a 50,000-mile stretch, our all-electric hybrids would use about 1,719 fewer gallons of fuel when compared to our standard diesel buses. At over 50,000 miles, this saves about $4,000 worth of fuel!

The diesel engines on our newest hybrids also run even cleaner, as they comply with 2013 EPA regulations as opposed to the less-strict standards from 2010.

We’re often asked about getting more hybrid, electric, biogas or compressed natural gas (CNG) buses. We’re considering all of these quickly-evolving technologies, but as we test them, we look for cost-effectiveness of a bus’ entire lifecycle before making wholesale changes to the fleet.

Shhhhh …

And they’re quieter than our other buses. They’ll still make some noise, but we’ve never put a bus on the streets that’s basically as loud as a typical passenger car. Folks who are visually impaired will still be able to hear it.

Down the road

We’ll watch how our newest hybrid buses perform on the streets to see if we’ll buy more of them. Battery technology continues to improve and buses are being tested that can go 200 to 300 miles (wow!) without a recharge. These hybrids just may be great transition toward all-electric buses in the future.

Andrew Longeteig

Andrew Longeteig

I’m TriMet’s Communications Coordinator. I share what’s happening at the agency with the media and general public. When I’m not working, I’ll either be watching the Blazers or at a rock concert.

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Sign of the times: Older MAX destination signs going digital

The iconic MAX destination signs on our “old” trains—those made between 1983 and 2003—are going digital.

We’re phasing out the older signs as we replace the communications systems on 105 train cars. Yes, this includes the old-school roll signs that have to be hand-cranked by our MAX operators (a time-consuming task).

Since last year, we’ve been installing LED destination signs on the front, side, interior and back of these trains so you can more clearly see—even on those dark, dreary December days—where your train’s headed. We’re also upgrading the speaker systems so you can hear us better and be able to listen to any special recorded announcements.

Doug Jones is a TriMet engineer working on the project. He says with the opening of the new MAX Orange Line, it didn’t make sense to buy new destination roll signs that included “Orange Line.” Plus, there was simply no room left on the old hand-cranked roll signs.

“It’s good timing to work on this project as we expand our MAX network,” Jones says. “It’s a more flexible system and improves service to our passengers.”

A destination roll sign prior to replacement.
A destination roll sign prior to replacement.
A new interior LED sign.
A new interior LED sign.

It takes six people about four days to strip out the old communications systems on a train and install the new equipment. More than one-third of the trains are done, but not without some challenges.

“Working on the oldest trains is more difficult than expected because we’re using the existing conduits that pipe underneath,” Jones says. “It takes a lot of effort to pull through the new cables because the space is tight.”

You’ll still see the older signs around for a bit longer. But don’t hold your breath—all MAX signs will be digital sometime in 2016.

Andrew Longeteig

Andrew Longeteig

I’m TriMet’s Communications Coordinator. I share what’s happening at the agency with the media and general public. When I’m not working, I’ll either be watching the Blazers or at a rock concert.

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Moving forward with cleaner, more energy-efficient buses

Our buses continue to become more fuel and emissions efficient.

Although our older buses consistently meet federal emissions standards, our newer buses—which make up about one-third of our fleet of 655— emit far fewer particulates into the air.

Why?

A big reason is our newer buses have a diesel particulate filter that removes soot from the exhaust. We’ve also retrofitted 196 of the older buses with these special filters, which remove at least 98 percent of the black powdery stuff.

Diesel particular filters removes most of the soot from the exhaust from our buses.
Diesel particulate filters remove most of the soot from our buses’ exhaust.

Our newer buses also emit less smog-inducing nitrogen oxide (NOx), a pollutant caused by fuel burned at high temperatures. The technology converts NOx into oxygen, nitrogen and water before it exits the tailpipe.

Smart sensors

Another technology that reduces fuel consumption by about five percent is called Sensotop. Made in Germany, it’s a shifting algorithm that uses sensors to change the gear-shifting calibration based on weight and terrain.

For example, a full bus going uphill requires more power—which Sensotop helps provide—while a bus with fewer people going downhill or on level roads requires less. These sensors are on all the buses we’ve purchased in the past three years, and we’ve also retrofitted 40 older buses.

Cool cooling system

In the transit world, we’re also pioneers of a NASCAR-inspired electronic cooling system that reduces engine drag, maximizes horsepower and improves fuel economy by up to 10 percent. Developed for military heavy equipment, it’s on about half our bus fleet. EPA actually gave us a Clean Air Excellence Award for helping bring the technology to the transit market (Woohoo!).

Improving MPG

Cars in the United States average about 25 miles per gallon. Our buses made in the early 1990s averaged about 4 miles per gallon. Our newer fleet typically gets between 4.5 to 5 miles per gallon with the added challenge of having air-conditioning systems, more electronic accessories and stricter emissions standards.

Getting an extra half-mile per gallon may not seem stellar, but for the scale of our vehicles, it’s a 12 to 25 percent improvement. And if you have 40 passengers on board who would have otherwise driven a car, it’s like getting 180 to 200 miles per gallon!

What’s next?

We’re buying 77 more buses by mid-2016 that will be low-floor, low-emission and air-conditioned. This purchase will help us get our fleet closer to an average age of eight years, the industry standard.

Riders often ask about getting more hybrid, electric, biogas or compressed natural gas (CNG) buses. We’re considering all of these quickly-evolving technologies. In fact, four of the latest generation HybriDrive® Series buses should hit the streets sometime in October. As we test these new technologies, we look for cost-effectiveness of a bus’ entire lifecycle before making wholesale changes to the fleet.

Learn more about our new buses

Andrew Longeteig

Andrew Longeteig

I’m TriMet’s Communications Coordinator. I share what’s happening at the agency with the media and general public. When I’m not working, I’ll either be watching the Blazers or at a rock concert.

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