Thus higher fuel efficiency was associated with lower traffic safety, intertwining the issues of fuel economy, road-traffic safety, air pollution, and carbon emissions. In the mid-2000s, increasing safety of smaller cars and the poor safety record of light trucks began to reverse this association. Nevertheless, in 2008, the on-road vehicle fleets in the United States and Canada had the lowest overall average fuel economy among first world nations: in North America, versus in the European Union and was even higher in Japan, according to data as of 2008. Furthermore, despite general opinion that larger and heavier (and therefore relatively fuel-uneconomical) vehicles are safer, the U.S. traffic fatality rate—and its trend over time—is higher than some other western nations, although it has recently started to gradually decline at a faster rate than in previous years.