Archive for September 16th, 2008

From The Age newspaper in Australia, via Drive.com.au, comes this surprising, sobering “anatomy of a crash,” the car in question being the 5-star Ford Falcon (the one made in Australia, not the one your father had when he was young).

The article leads by noting: “Survivors of serious car crashes often say time appears to slow down in the moments around the impact and that they can recall the event in extraordinary detail.” (and somehow the images we always see of crash-test dummies in slow motion tends to reinforce that).

But an actual reconstruction of the events shows the sort of reshuffling of the deck the brain is playing with memory:

“This is a reconstruction of a crash involving a stationary Ford Falcon XT sedan being struck in the driver’s door by another vehicle travelling at 50 km/h.

One millisecond equals 1/1000th of a second.
0 milliseconds - An external object touches the driver’s door.
1 ms - The car’s door pressure sensor detects a pressure wave.
2 ms - An acceleration sensor in the C-pillar behind the rear door also detects a crash event.
2.5 ms - A sensor in the car’s centre detects crash vibrations.
5 ms - Car’s crash computer checks for insignificant crash events, such as a shopping trolley impact or incidental contact. It is still working out the severity of the crash. Door intrusion structure begins to absorb energy.
6.5 ms - Door pressure sensor registers peak pressures.
7 ms - Crash computer confirms a serious crash and calculates its actions.
8 ms - Computer sends a “fire” signal to side airbag. Meanwhile, B-pillar begins to crumple inwards and energy begins to transfer into cross-car load path beneath the occupant.
8.5 ms - Side airbag system fires.
15 ms - Roof begins to absorb part of the impact. Airbag bursts through seat foam and begins to fill.
17 ms - Cross-car load path and structure under rear seat reach maximum load.
Airbag covers occupant’s chest and begins to push the shoulder away from impact zone.
20 ms - Door and B-pillar begin to push on front seat. Airbag begins to push occupant’s chest away from the impact.
27 ms - Impact velocity has halved from 50 km/h to 23.5 km/h. A “pusher block” in the seat moves occupant’s pelvis away from impact zone. Airbag starts controlled deflation.
30 ms - The Falcon has absorbed all crash energy. Airbag remains in place. For a brief moment, occupant experiences maximum force equal to 12 times the force of gravity.
45 ms - Occupant and airbag move together with deforming side structure.
50 ms - Crash computer unlocks car’s doors. Passenger safety cell begins to rebound, pushing doors away from occupant.
70 ms - Airbag continues to deflate. Occupant moves back towards middle of car.
Engineers classify crash as “complete”.
150-300 ms - Occupant becomes aware of collision.”

What’s fascinating about all this is not simply the rapid fire technology at work (I’m still trying to deal with that computer deciding whether it was a shopping trolley or another car that has struck), but how much has gone on before we even register it — and this at 50 km (31 mph), so you can imagine what’s happening at higher speeds — even though in our subsequent reconstruction of events we may have imagined that time actually slowed down the during the event.

I couldn’t help but think of the work of David Eagleman, of the Baylor College of Medicine, in this regard. In his paper “Does Time Really Slow During a Frightening Event?”, Eagleman, through some clever techniques involving a (somewhat paradoxical) “controlled free-fall system,” found that rather than time actually slowing, a la the fight scenes in The Matrix, what seems to be going on, the researchers speculated, is “that the involvement of the amygdala in emotional memory may lead to dilated duration judgments retrospectively, due to a richer, and perhaps secondary encoding of the memories. Upon later readout, such highly salient events may be erroneously interpreted to have spanned a greater period of time.”

In other words, because of the nature of the event, people may have had, essentially, more of a memory of it, so when they later thought of it, it took longer to “replay.” But in the case of the Falcon, the event was essentially over before the driver would have realized what was happening.

An alert reader sends along some more coverage, this time by Isabelle de Pommereau in the Christian Science Monitor, of Bohmte, a German village that has become another waypoint in the evolving “Shared Space” movement (I was in the town a few years ago, for a Shared Space conference, but haven’t been back since things were changed). The town, like many, felt overwhelmed by the 13,000 vehicles per day coursing through its small center.

Readers of the book and blog by now may well know the drill:

“But this summer the town reworked its downtown thoroughfare, not only scrapping the traffic lights but also tearing down the curbs and erasing marked crosswalks. The busiest part of the main street turned into a “naked” square shared equally by bikes, pedestrians, cars, and trucks. Now, there is only one rule: Always give way to the person on the right.”

Bohmte is providing yet another surprising example of the types of environments in which this sort of thing can be done: “What’s revolutionary about Bohmte is that it took off its signs on a state highway with a lot of traffic,” says Heiner Monheim, a traffic management expert at the University of Trier, speaking at a recent European conference on sign-free towns convened here. Beyond that, Monheim says, the model’s real legacy is to have brought people closer to “rediscovering and appreciating cities not only as traffic places but also as human, social places.”

But I was also struck in particular by this passage:

“Two months into the experiment, ‘Instead of thinking, ‘It’s going to be red, I need to give gas, people have to slow down, to look to the right and the left, to be considerate,’ says Ms. Rubcic… The bonus? Town people recognize they have become a bit closer to one another. ‘The whole village has become more human. We look at each other, we greet each other,’ she says.”

From the new Harper’s Index:

“Percentage by which the average incidence of fires and traffic accidents on Fridays the 13th differs from that of other Fridays: —4.”

The index also features this curious entry: “Number of additional road deaths that would have been caused by a ‘gas-tax holiday’ this summer: 66.”

They give the enemy clear directions. This from the wonderful little book, The Original Highway Code, which reprints earlier editions of the perennial British bestseller.