Monday, September 7, 2009

Public Safety vs. Public Safety

"A minute is a long time to wait if you're not breathing."

I tried it out while researching this post, and concede that the fire chief who made this comment has a point.

It's a concern that comes up frequently in debates over installing traffic calming devices on streets where high speeds hinder pedestrian safety. Pedestrian advocates argue that slowing down traffic improves walkability and reduces pedestrian injury. Fire departments contend that in a life-threatening emergency every second matters, so it's counterproductive to introduce obstacles to vehicle travel.

So who's right? Good question.

Research on emergency response times has centered on cardiac arrests, as there's reasonable consensus that time is of the essence when your heart has decided to stop beating. In general this research shows that response times under five minutes produce the best results in terms of survival (not to depress you, but this does not necessarily mean the survival rates are high when a victim is reached within the five minute window--just better than they would be otherwise). Many fire departments set a goal of responding to 90 percent of life-threatening calls within five minutes, and the LAFD appeared to be achieving that goal--at least prior to its recent budget cuts.

While there hasn't been much investigation of how traffic calming measures impact emergency response times, the work that is available (summarized in this report by Reid Ewing) suggests that speed humps and traffic circles slow down emergency vehicles by 3-14 seconds per measure. The biggest delays are to the largest vehicles, so an ambulance won't be slowed as much as a ladder truck.

By these estimates, a series of traffic calming measures along an emergency route could conceivably delay responders enough to be problematic--at least for cardiac events. But only if emergency response times were right at the cusp of five minutes, or if vehicles were confronted with a whole slew of traffic calming measures in a row. Given this, it doesn't necessarily follow that all traffic calming is a bad idea; in areas with high pedestrian traffic the benefits of improved pedestrian safety might outweigh the costs of slower response times.

I don't mean to downplay the importance of timely emergency response, but it's important to recognize that rejecting traffic calming measures based simply on blanket assertions instead of case-by-case evaluation could actually harm public safety. I'm hoping decisionmakers are sophisticated enough to recognize this...but I won't hold my breath.

Saturday, August 29, 2009

Where the Sidewalk Really Started

London, in case you were wondering.

It all began with a 1764 survey of the local infrastructure by the Commission of Sewers and Pavements (one can only imagine the sins a bureaucrat had to commit to end up on the sewer commission). The commission found that London roads were “defective, even in the principal streets.”

Apparently 18th century Londoners hated walking on cracked pavement and muddy roadway shoulders as much as we do today, because a year later concerns over the commission's findings prompted the creation of the city's first curbed sidewalk. Other cities followed suit, and by 1823 Paris had even enacted a law requiring property owners to install sidewalks adjacent to their buildings. (No one paid much attention to it, as these were the days before binding developer agreements.)

Of course, pedestrians had been on the minds of city leaders long before the apperance of sidewalks. Heavy traffic congestion led Julius Caesar to ban the use of cars and chariots between sunrise and sunset on the roads of ancient Rome--though (no big surpise) he reneged on an earlier promise to grant pedestrians the right of way over other road users. Nor did other pledged improvements, such as road paving, ever materialize.

In fact, it wasn't until 1,000 years after Caesar's reign that paving began in earnest throughout Europe (Paris began the trend in the late 1100s). Paved roadways made walking easier for pedestrians in medieval cities...but it also made walking easier for horses, oxen, and other types of "heavy vehicle" traffic.

The increasing chaos on city streets got architects thinking about how to design city transportation networks that served everyone. Leonardo da Vinci recommended that the problem be addressed by separating pedestrians from other forms of traffic. Here is one of his drawings from the late 1400s, showing how the concept might look:



Although his designs weren’t adopted at the time, da Vinci's vision of pedestrian-only spaces was prescient-- today you can find "pedestrianized" streets everywhere from New York to Costa Rica.

Friday, August 28, 2009

Cool Pedestrian Stuff #3: "Divans"

A 1911 New York Times article describes this "novel auto invention" that was intended to prevent vehicles from knocking down and crushing pedestrians. As the article explains, the "scissorlike fender" attached to the front of private vehicles and streetcars and scooped up errant pedestrians, bearing them along in a "sort of divan" until they could be safely deposited elsewhere. The inventor claimed that the device had been proven effective at vehicle speeds up to 60 mph, though I'm skeptical that any encounter with an object traveling so fast--no matter how cushy--would be comfortable for a pedestrian. (Of note: the article blames these crashes on the "careless pedestrian" who steps thoughlessly in front of moving vehicles. Hmm, sounds familiar.)

Researchers today continue to investigate solutions for decreasing the impact (sorry, bad pun) of pedestrian crashes. One solution is to create vehicles that can sense when they are hitting pedestrians and implement appropriate safety mechanisms. In this example, designed by Bosch, the vehicle automatically raises its front hood when it hits a pedestrian to help decrease pedestrian injury.

Tuesday, August 25, 2009

Enough already. Seriously.

A 60-year-old woman and her dog were killed crossing Shoreline Drive in Ventura on Monday. Although there was a marked crosswalk nearby, the two were not using it when they were struck.

Here's hoping the rule of threes applies in this case, and we won't see any more pedestrian deaths for a while...

Sunday, August 23, 2009

A bad weekend for pedestrians

The LA Times reports that a 10-year-old boy was killed and several other members of his family were injured when a driver hit them as they were crossing Tweedy Boulevard in South Gate. The crash occurred when the driver made a left turn from San Vicente Boulevard (which has a stop sign) onto Tweedy Boulevard. The family was walking inside a marked crosswalk that has a brick-style treatment to distinguish it from the rest of the road.