Two transportation-related tragedies in recent weeks -- the collapse of a bridge in Miami and the death of a woman in Arizona who was struck by an autonomous Uber car -- have shined a light on the challenges of deploying new infrastructure technologies.

But the two incidents also highlighted something else, according to many safety advocates: the inadequacies of legacy designs when it comes to pedestrians.

And they come as pedestrian deaths have been climbing. The Governors Highway Safety Association estimates there were 6,000 pedestrian deaths in 2017. That's essentially unchanged from the year before -- but 2016 saw a higher level of pedestrian deaths than the country had seen in 25 years.

In Tempe, Ariz., an autonomous vehicle from Uber struck and killed a pedestrian while going 40 mph on a dark street on March 19. Most of the attention so far has been on Uber’s driverless technology and whether the company was testing that technology responsibly. But some safety advocates have also questioned whether the design of the street itself played a role, because it gave pedestrians no convenient, safe place to cross.

The pedestrian, Elaine Herzberg, was walking her bike across the street when she was killed. Although there was a bike lane along the road, a brick path through the median was marked with a sign indicating pedestrians weren’t allowed. The sign says “Use crosswalk,” with an arrow pointing to an intersection 500 feet away, where two six-lane roads meet. The brick path with the no-pedestrian sign appears to be directly across the street from a dirt path.

Arizona has seen a recent surge in pedestrian fatalities. The number of walkers who died jumped from 197 in 2016 to 224 last year. In a one-week span shortly before the Uber crash, 10 pedestrians were killed in the Phoenix area. A recent report showed that Arizona had the highest pedestrian death rate, per capita, in the country.

The Uber death came just three days after the collapse of a pedestrian bridge in Miami killed six motorists. The Miami tragedy raised a different set of questions about pedestrian infrastructure, but with a similar underlying concern: Was the massive pedestrian bridge being built for the convenience of pedestrians, or for the motorists who traveled under it?

Florida International University chose a new technology, called accelerated bridge construction (ABC), to erect its $15 million, 289-foot-long pedestrian bridge. The chief benefit of that approach is that it limits the amount of time the road below needs to be closed to traffic. But the pedestrian bridge itself would have also benefited motorists, because it would have limited the time cars had to sit at red lights waiting for walkers to cross.

The pedestrian bridge, though, would not have addressed larger concerns about the safety of Eighth Street, the arterial road that passed beneath it. Seventeen people died on a four-mile stretch of the road between 2007 and 2012, and one FIU student died there just last fall. But local planners were looking for ways to ease congestion -- in other words, speed traffic up even more -- on the major thoroughfare.

For many safety advocates, both situations appeared to be the result of transportation officials prioritizing the quick movement of cars over the safety of pedestrians.

“An effective approach to traffic safety would consider the dangerous conditions for pedestrians that led to the construction of the [Miami] bridge in the first place,” writes Angie Schmitt of Streetsblog, a site that advocates for less car-centric infrastructure. “If we don’t think critically about these systemic risks, our transportation networks will keep on failing at public safety.”

Victor Dover, a Miami architect who promotes “livable communities” over sprawl, says pedestrian bridges show planners’ concerns about cars and motorists.

“The thing is, ‘pedestrian bridges’ are not really about providing safety and delight to pedestrians,” he writes. “The real purpose of the bridge was to reduce the pesky crosswalks and speed up traffic, to minimize signal phases when motorists would have to wait for people to cross on foot. Meanwhile, the effect of such bridges is to permanently surrender the at-grade pedestrian experience.”

Dover and Kenneth García, a town planner with the same firm, even designed an alternative to Eighth Street’s current configuration to illustrate how the road could become more pedestrian friendly. It includes transit, but not the pedestrian bridge.

“The Eighth Street of the future should have multiple places to cross at intersections where pedestrians are on an equal footing with cars, matched up with multiple walkways over the canal to Sweetwater and other neighborhoods. In our illustration, there are more traffic signals, not fewer, with broad high-visibility crosswalks. And yes, traffic will move more slowly.”

Linda Bailey, the executive director of the National Association of City Transportation Officials (NACTO), says the public’s initial reaction to the autonomous vehicle crash in Arizona said a lot about how the American public, and even local leaders, view pedestrian deaths.

“It brought out all the things that we hear when a pedestrian is killed, especially because the pedestrian is not around to tell the story. We hear about how it was dark, the pedestrian came out of nowhere, that she was not in the crosswalk,” Bailey says. “It’s really indicative of how we treat pedestrian deaths in general. We are still focused on idea that people who died in traffic in the United States did something wrong. It’s pervasive. Most people don’t know anything else.”

Indeed, Sylvia Moir, the Tempe police chief, remarked after watching video of the crash taken by the Uber car that “it’s very clear it would have been difficult to avoid this collision in any kind of mode [autonomous or human-driven] based on how she came from the shadows right into the roadway.”

But Bailey says the crash also shows design flaws in how many roads are built.

“It does point out that the roadways there are designed for unsafe speeds for pedestrians. It’s a remnant of the highway and mini-highway era, where engineers set speed limits as high as possible and pedestrian crossings are viewed as slowing down traffic,” she says.

But that type of engineering doesn’t reflect how non-motorists actually use the roads.

“We have to engineer for actual human behavior. There are no hardware or software upgrades for actual human beings.”

NACTO has long pushed for autonomous vehicles to be limited to 25 mph or less in areas where pedestrians are likely to be present -- not just in downtowns. At that speed, pedestrians are much more likely to survive a crash with a vehicle, which is a major reason why many cities that have adopted the Vision Zero safety strategy have lowered their speed limits to 25 mph.

“People want to be able to hit the gas between red lights,” Bailey says. “As transportation officials, we have to ask ourselves, are we designing a safe system or not?”

Of course, street design did not change overnight to suddenly imperil more pedestrians. And pedestrian deaths have not risen at the same rate on all roads.

Take Arizona, for example.

“Over the past five years, the total number of pedestrian-related crashes on the [Arizona] state highway system has remained consistent,” the Arizona Department of Transportation told Governing in a statement. “An increase in pedestrian-related crashes has occurred on other roadways, including city streets and county roads. In Arizona, more than 80 percent of pedestrian fatalities occur on these other roadways.” The Uber crash did not occur on a state road.

The state department will also fund projects to reduce fatal and serious-injury crashes as part of its highway safety improvement plan.

Alberto Gutier, the director of the Arizona Governor’s Highway Safety Office, says the biggest change he’s seen is just the sheer number of people on the road, whether they be drivers or pedestrians, as the state’s population has grown.

But he also sees lots of problems in people’s behavior.

“The problem is that people don’t cross in the crosswalk. People looking at their stupid phones. They’re crossing the tracks of the light rail [in the Phoenix area] after they get off, going between cars” in the middle of the block.

At the same time, though, drivers are often so eager to turn right when the light changes that they forget to look for pedestrians, Gutier says.

“We have dumb, stupid, idiot drivers."

Gutier’s office recently secured funding to start “selective enforcement” actions in more than 20 cities in Arizona’s major metropolitan areas. He wants cops on bikes, especially, to confront people who cross streets illegally, although motorists will also be included. The goal, he says, is to change people’s behavior, not to give them tickets.

“I’m not promoting ticket, ticket, ticket, but I’m sure somebody will get a ticket.”

But Gutier says he is also impressed by the work of New York City, where he once lived, to prevent pedestrian deaths. New York City is one of the most aggressive in rolling out Vision Zero. Like other safety campaigns, Vision Zero relies on public education and aggressive enforcement of certain traffic laws. But the biggest difference is its emphasis on building safer infrastructure, so human error doesn’t lead to human deaths.

Better infrastructure sounds good to Gutier, and he’s encouraged by the state transportation department’s work on a pedestrian plan. “But it’s millions of dollars we don’t have in the highway safety office, and I don’t know if ADOT can get it,” he says.

Gutier has hung up print-outs of the New York projects in his office. But he says he hasn’t yet talked with his boss, Gov. Doug Ducey, about implementing those sorts of changes in Arizona.