Sightline Institute reports that drivers in the Northwest states of Idaho, Oregon, Washington used more gasoline last year, reversing a decade-long trend of declining personal gas consumption. Per capita consumption increased slightly in 2009, while total consumption rose by 2%. Lower fuel prices boosted consumption.

Idaho drivers—already the highest per-capita consumers in the region—led the Northwest by increasing their gasoline purchases by nearly 4%. Washington and Oregon saw per capita increases of less than 1%, which is a departure from the states’ nearly uninterrupted decline since 1999.

Despite promises of a low-carbon Olympics, the economic activity spurred by the preparations for the Winter Games contributed to a 10% increase in per capita gasoline sales in British Columbia—the largest single-year gain in at least 30 years. The report notes that the increase occurred despite BC’s groundbreaking carbon tax, which is designed to reduce greenhouse gas emissions.

Per capita diesel use was also up in BC, though at a

more moderate pace. Despite these increases, residents of BC still consumed roughly 25% less gasoline and diesel, on average, than residents of the Northwest states.

While gasoline use went up, last year also brought a decline in the Northwest states’ consumption of diesel—a fuel closely related to trucking and other commercial activity.

The report also describes how different policies could put the Northwest back on track for cutting gasoline consumption—ranging from pollution fees to comprehensive energy and climate policy, such as a carbon tax or cap-and-trade system.