Several global factors are likely to get Americans behind the wheel to spend some of the Memorial Day weekend in the car. A struggling global economy, stronger dollar, and fewer immediate concerns about events in the Middle East have pushed crude prices down $10 a barrel since the beginning of the month. Gasoline prices have dipped below $4 a gallon in New England and elsewhere. While the drop is only symbolic, since prices at the pump are still high and probably going higher, it makes people feel good, says Chris Christopher an economist with IHS Global Insight. "Maybe they'll spend a bit more or have a nicer vacation because of it."