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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