With the number of pedestrians struck and killed by vehicles in the U.S. climbing to a 28-year high, safety regulators are sounding the alarm.

"This is a wake-up call. We need to do much better keeping pedestrians from being hit and killed," said David Harkey, president of the Insurance Institute for Highway Safety.

The IIHS studied crashes that lead to the death of pedestrians to determine why the numbers have spiked in recent years.

In 2016, 5,987 pedestrians were killed in traffic accidents, the highest number since 1990. Even more alarming to the institute: The 46 percent increase in pedestrian deaths since 2009 far outpaces the 11 percent rise in total traffic deaths over the same period.

What's behind the increase?

"When you look at the data, it is clear many of these fatalities are happening after dark on the busiest streets, often when people try to cross somewhere other than a designated crosswalk," said Harkey.

In addition, the institute believes higher speed limits in many municipalities mean a deadlier outcome when pedestrians are hit.

The institute is calling for city and state governments to do a better job lighting and designating intersections and pedestrian crosswalks.

What about drivers and pedestrians being more distracted and failing to stop a vehicle in time or look before crossing a road?

"We've all seen those stories where someone is distracted and it lead to an accident, but quantifying how much of a role distraction played in pedestrian accidents is very difficult."

Meanwhile, automakers are slowly adding technology to vehicles to prevent pedestrian collisions. Harkey pointed out that Subaru's EyeSight system has been particularly effective in cutting pedestrian accidents.

"Subaru's EyeSight technology has lead to a 35 percent reduction in pedestrian accident-related insurance claims," Harkey said.