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The number of pedestrians killed along U.S. roadways last year climbed to the highest level since 1990, according to a new report.

An estimated 6,227 pedestrians were killed in 2018, an increase of 250 from 2017, the Governors Highway Safety Association said Thursday. The association based its estimate on data collected by state highway safety offices.

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"The alarm bells continue to sound on this issue," Executive Director Jonathan Adkins said in a release about the rising number of people hit and killed by vehicles. "It's clear we need to fortify our collective efforts to protect pedestrians and reverse the trend."

U.S. pedestrian fatalities have increased 41 percent since 2008 and now account for 16 percent of all traffic fatalities, the association said.

Why are more people being killed by vehicles?

For starters, America's growing love affair with pickups, SUVs and crossover utility vehicles means pedestrians are being hit by bigger, heavier, and more powerful vehicles. As a result, pedestrians who are hit are more likely to die or suffer life-threatening injuries, the association said. Pedestrian fatalities involving SUVs jumped by 50 percent between 2013 and 2017, it estimates.

Another factor is the growing population in many states, which has lead to more deadly encounters between drivers and pedestrians. The report also blames people being distracted by their smartphones and not being focused on the road as contributing to pedestrian fatalities.

Add in a strong economy with relatively cheap gas prompting more people to drive more miles and it's a deadly recipe for people walking along roads or crossing streets.

The association estimates that five states — Arizona, California, Florida, Georgia and Texas — accounted for almost half the pedestrian fatalities in the first half of 2018. The report says New Mexico had the highest pedestrian fatality rate per 100,000 residents in the first half of last year while New Hampshire had the lowest fatality rate.