The Limitations Of Hybrid Buses

E-Tran was created for this fast growing Sacramento suburb just one and one half years ago. The fleet was entirely composed of new, hybrid-electric diesel buses, but fast growing ridership and mechanical problems resulted in the addition of, ironically, much older and polluting diesel buses, but apparently far more reliable on the regional routes.

"So, what's the problem with the hybrids? They perform best during stop-and-go traffic, Transit Manager Carlos 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."