Monday, August 21, 2006

Hybrid Buses for the Long Haul?

Live from the Third Rail describes some of Elk Grove's e-tran's growing pains. The Sacramento Bee reports (registration required, Third Rail provides a pdf.) It seems that e-tran's hybrid buses aren't up for the long routes using freeways:
A hybrid-powered commuter bus fleet -- the cleanest in the nation -- would be the heart of what's called the e-tran.

But now, Elk Grove's path to clean-air mass transit has taken a detour. Diesel buses, both chartered and purchased, currently make up nearly half of e-tran's 42-vehicle fleet and most of the daily commute buses to downtown Sacramento.

Instead of cruising into the nation's history books, the hybrid fleet has had trouble accelerating into the fast lanes of the freeways. Instead of comfortable rides, hybrid bus air conditioners have quit in triple-digit temperatures, leaving passengers sweating in ovenlike heat.

Now, only five of the city's 21 hybrids are used on freeways.

"In the quest to be leading edge, you have to take chances at times on new technology," Mayor Rick Soares said. "We took that chance."
So, what's the problem with the hybrids? They perform best during stop-and-go traffic, Tobar said. The hybrid's electric energy booster, an ultra capacitor, works in tandem with a 145-kilowatt generator. That booster is recharged every time a driver applies the brakes.

That's great for intercity transit, but is troublesome on freeways where brakes are less often applied.

"At highway speeds, many of the systems are stressed," Tobar said.

Among the stresses are air conditioners that switch off on ultra-hot days during freeway travel. To relieve passengers, Tobar either pulls buses from service or delivers bottled water in ice buckets to buses on afternoons hotter than 105 degrees.

Still, passengers have been howling. With sunlight beating into bus windows, the hybrids have been compared to rolling hot houses.

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