GEOFF BENNETT: By many measures, advancements like seat belts and airbags have made vehicles dramatically safer for drivers and passengers.

But as our cars get bigger and bigger, what about the safety of those outside of our vehicles?

Ali Rogin reports on how federal regulators are looking at pedestrian safety now and whether new rules can help curb the rising number of people killed on our streets each year in the U.S. JESSICA HART, Mother: So these are all from her last summer.

ALI ROGIN: Jessica Hart is showing me photos of her daughter, Allison, or Allie, as her friends and family called her.

JESSICA HART: This is totally her, Running through the water, just joyful in her own skin.

ALI ROGIN: I love how so many of these pictures, she's in motion, she's jumping and... JESSICA HART: Yes.

Yes.

She didn't need all the things to just have fun and run around and be happy.

ALI ROGIN: In September of 2021, Allie's life was tragically cut short.

She was killed while riding her bike with her dad near their house in Washington, D.C. Allie was just 5 years old.

JESSICA HART: They were going down the sidewalk, and she went into the intersection of a four-way stop.

She was on the crosswalk in a school zone, and the driver of a van didn't make a full stop and see her and hit her.

And we think she died on impact.

ALI ROGIN: City law enforcement officials didn't file any criminal charges against the van's driver, who remained at the scene.

Allie was one of more than 8,000 pedestrians and cyclists killed that year.

JESSICA HART: It breaks my heart every day.

So her last moments were moments of terror.

And I wasn't there with her, and her dad was there, and it breaks his heart every second that he couldn't save her.

It's just -- it's awful.

ALI ROGIN: Over the past 15 years, pedestrian and cyclist deaths on our roads have increased dramatically.

As of 2022, fatalities and crashes with motor vehicles were up more than 80 percent.

But, in September, the National Highway Traffic Safety Administration, or NHTSA, proposed a new safety standard to better protect pedestrians, mandating that new vehicles be designed to reduce the risk of serious to fatal pedestrian crashes and test what happens when hoods make contact with heads.

ANGIE SCHMITT, Author, "Right of Way: Race, Class, and the Silent Epidemic of Pedestrian Deaths in America": I was really excited to hear about it.

I feel like NHTSA has been really hands-off on this issue, and it's got -- there's been a lot of real-world harm.

ALI ROGIN: Angie Schmitt is an urban planning consultant and the author of "Right of Way: Race, Class, and the Silent Epidemic of Pedestrian Deaths in America."

Should regulators have acted sooner?

ANGIE SCHMITT: Yes, I think so.

And, actually, in Europe and in some parts of Asia, they have required certain features that are designed to protect pedestrians, particularly to the front end of cars, since about 2009.

So we're way behind them.

And these new regulations do not go as far as what they're already doing in Europe.

ALI ROGIN: The Alliance for Automotive Innovation, an auto industry trade group, is still reviewing the proposed rule and said in a statement: "Safety is a top priority.

Automakers have voluntarily developed and introduced many crash-avoidance technologies to help make roads safer for pedestrians and road users."

Part of what makes the U.S. unique is that our cars keep getting bigger.

The average U.S. passenger vehicle has grown four inches wider, 10 inches longer, and eight inches taller over the last 30 years, according to the Insurance Institute for Highway Safety, or IIHS.

JESSICA CICCHINO, Senior Vice President For Research, Insurance Institute for Highway Safety: We do know that larger vehicles like SUVs and pickups are deadlier for pedestrians when they're in crashes with them.

ALI ROGIN: Jessica Cicchino is senior vice president for research at IIHS.

In a paper published last month, she and her co-authors found that taller and blunter front ends were associated with significant increases in pedestrian fatality risk compared with shorter front ends.

JESSICA CICCHINO: When we see those tall, blunt front ends, that's when we see that the pedestrians are especially likely to be thrown forward.

That's the feature that we have really seen has made the most difference in pedestrian injury severity.

ALI ROGIN: While Cicchino thinks NHTSA's proposed rule is a step in the right direction, she also points to another safety feature that can prevent some crashes altogether.

On a covered test track at IIHS' research center in Virginia, we got a firsthand demonstration of pedestrian Automatic Emergency Braking, or AEB, which will be required as a standard feature on all new vehicles by 2029.

MAN: OK, ready here.

ALI ROGIN: As the vehicle cruises at 25 miles per hour, a warning, and then automated braking to prevent contact with a pedestrian who has entered the roadway.

DAVID AYLOR, Vice President for Active Safety Testing, Insurance Institute for Highway Safety: Early on, for pedestrians, the systems didn't perform as well.

ALI ROGIN: David Aylor is vice president for active safety testing at IIHS.

He says that in the group's tests, AEB systems have improved significantly.

DAVID AYLOR: Back then, not all cars were able to avoid.

It was often optional equipment on a lot of luxury vehicles.

Now the technology is pretty much standard, and we're now recognizing other vehicles, as well as pedestrians, motorcycles, other targets.

And so, even in 10 years, we have come a long way.

ALI ROGIN: Automakers have raised concerns about the feasibility of meeting NHTSA's 2029 deadline for pedestrian AEB.

But either way, there will still be a significant lag before researchers expect to see an impact.

JESSICA CICCHINO: It could be up to 30 years before nearly all vehicles in the fleet have it.

And regulation takes a long time.

ALI ROGIN: IIHS' Cicchino says we need an all-of-the-above approach to pedestrian safety and can't just rely on new technology.

JESSICA CICCHINO: So, we're looking at designing roadways that are safer for pedestrians to cross, lowering speeds.

Those are all things that we can get to faster, where we can start trying to chip away at these increases in deaths right now.

ALI ROGIN: Back in Washington, D.C., a study from the city's Department of Transportation identified the intersection where 5-year-old Allie Hart was killed as needing a crosswalk update in 2015.

But the plastic posts, signs, and added visibility only came after Allie's death in 2021.

JESSICA HART: I mean, nothing will bring Allie back for us.

But when you still see drivers day after day slow and roll into the crosswalk and clearly not look for pedestrians, you just know that that's not enough.

MAN: Jessica Hart, I have got you up first.

So let me turn to you for your testimony.

Good afternoon.

ALI ROGIN: Jessica and her husband, Bryan, have become active with Families for Safe Streets, an advocacy group with chapters around the country made up of people whose loved ones were killed or injured in crashes.

JESSICA HART: I hope that by sharing what happened to Allie and our family, it makes people realize, first of all, that it could happen to anybody.

When you think about 40,000 people a year, every year dying on our streets and roads across the country, and, still, we just collectively shrug.

And I can't understand it, and it makes me just furious.

ALI ROGIN: But as new rules come into view, questions remain about whether drivers will stop to notice.

For the "PBS News Hour," I'm Ali Rogin in Washington, D.C.