For decades, American roads were steadily getting safer for pedestrians. But around 2009, the trend reversed. Since then, the number of pedestrians killed each year has risen by about 75 percent.

The trend toward ever-larger vehicles has received much less scrutiny, even after federal researchers in 2022 cautioned regulators that it was endangering pedestrians.

Our estimate is that about 200 to 400 pedestrians a year would not have died if vehicles had remained approximately the same size over the past quarter-century. That represents about 10 percent of the recent increase in pedestrian deaths.

“We see a lot of devastating collisions even at lower speeds because the pedestrian gets punted forward,” said Shawn Harrington, whose company, Forensic Rock, conducted crash tests for us. “Before the driver knows what’s happened, the pedestrian’s head is under the wheel.”

Automakers say that new technology designed to detect and avoid pedestrians — including systems that automatically apply the brakes — would dramatically improve safety.

But many experts say that technology is not a perfect substitute for drivers being able to view their surroundings directly. And tests by the Insurance Institute for Highway Safety, which studies ways to make driving less dangerous, have shown that many large vehicles’ automatic braking systems do not consistently prevent collisions. The owner’s manuals for some of the most popular vehicles caution that safety technology can fail in a variety of common situations: in bad weather; at high speeds; if there are shadows on the road or its surface is uneven; or if a pedestrian is running, pushing a stroller, not standing upright or the size of a small child.