[SystemSafety] Royal College of Paediatrics weighs in

From: Peter Bernard Ladkin < >
Date: Wed, 19 Nov 2014 07:19:03 +0100


Continuing our critically acclaimed series concerning Guardian outtakes on UK child road safety:

http://www.theguardian.com/uk-news/2014/nov/18/children-doctors-20mph-speed-limit

Some numbers jump out. 25 children died as pedestrians in urban areas in 2011, compared with 311 adults. So child-urban-pedestrian deaths are (were in 2011) less than 1% of road deaths overall in the UK. Some observations:

The dynamics of a typical collision are
1. Perception by one or more participants of a space conflict, an imminent collision (stages PA, Perception and Attention, of a PARDIA sequence. "Perception" refers to circumstances being presented to a sensory field; "Attention" to them being cognitively registered. Informal use of the word "perception" commonly refers to both stages, but we found it appropriate to separate them for accident analysis);
2. Latency between perception and action (representing RD: Reason and Decision; the cognitive formulation of a course of action). In an unanticipated situation, this commonly takes between 1 and 2 seconds. (German traffic law says "1 second". In keeping with Napoleanic law, it is normalised, and as so often the normalisation of the phenomenon is not bound well to the reality.) 3. The decision made on the action. For a more-than-two wheeled-vehicle operator, usually some combination of swerve; brake; do nothing. For a two-wheeler, including bicycles, add lay-down. 4. The executed action (here the IA parts together: Intention and Action. They are separated in PARDIA primarily to account for the phenomena in GLOC incidents, which don't occur in road traffic).

Relatively few collisions occur without a progression through these stages. The stage 4 events change the dynamics of the collision: the incidence of the trajectories and the relative velocity. And of course it is the dynamics of the collision which largely determine the damage, along with the 3D spatial configuration of the participant objects. These causal factors are constrained by the initial conditions (trajectories before the PA of PARDIA; 3D spatial configuration of participants) but I would propose that the initial constraints are not as determinant of outcome as traditional approaches to road safety suggest.

In 2011, I considered motorway Auffuhr accidents, which have been occurring regularly (but thankfully rarely) on motorways/freeways/autobahnen in Western Europe and the USA for at least 60 years, and are usually put down somehow to irresponsible driving behavior. They are in fact system phenomena and this is easy to show: they result from rational decision making on the part of multiple operator/participants with limited mutual communication - and a relatively rare property of the environment. Indeed, I imagine similar conditions, decision making and behavior occur far more regularly than the accidents. The crucial difference is the relatively rare environmental property.

Nevertheless, we may expect the accidents to carry on happening and the police and judicial authorities in some countries continuing to seek out participants to blame. Yet systems analysis shows this is a fundamentally mistaken approach. Systems analysis is a foreign discipline to professionals in road safety. We could change that.

In 2012, I performed a qualitative systems analysis of same-direction spatial conflicts. It took me at least a week just to derive an appropriate ontology. For example, it turns out that one doesn't need 2D-continual trajectories. It suffices for the decision-theoretic analysis to consider trajectories akin to specific configurations of railway tracks. The analysis gets quite complicated (I didn't spend enough time to make it simpler) and remains incomplete. I should really get around to finishing it.

Unlike some here, I regard road safety as the most pressing system safety issue most of us encounter. There are system-safety issues with living in buildings, but these at least in Germany are a tenth of the size - about 600 people die in building fires in Germany each year; 5000 or so die on the roads.

(Apropos indirect-electrical-safety: about a third of fatal building fires are solely caused by electrical faults. Let's say that's 600/3= 200 deaths. Whereas only 15 or so people die each year directly from electrocution. So the real electrical-safety issue lies in implementing effective arc-fault detection in building circuits. The detectors do exist, thanks to aerospace initiatives which I looked at a decade ago, but an arc-fault-detection/protection device costs upwards of ten times the price of the usual Class A residual-current + short-circuit + overcurrent protection, which costs a tenth of the price. Nevertheless, I am thinking of spending the thousand or couple thousand euros it would cost to equip all my building circuits with arc-fault detection/protection. I do have pervasive smoke detection, and a climbing rope and good anchor on the top floor with the bedrooms. I did check I can still rappel half a decade ago. But I don't insist that visitors can....... The social cost-benefit analysis doesn't yet work for regulation: VSL is way lower. But *my* life is worth way more to me than VSL.)

I should note, apropos some recent comments here, that many road safety issues are country-specific. For example, the single most prominent factor in rural bike-car collisions in Germany is a specific roadway configuration which doesn't exist in the UK. Also, there are many urban bicycle-pedestrian conflicts in Germany from the provision of cycle paths on the sidewalks. That doesn't occur in the UK either. Or in the Netherlands, where city cycle paths are separated from pedestrians, and often from the motorised-traffic roadway. Many pedestrians, even those who have grown up with the system, wander all over the German urban cycleways without looking. Some cities, such as Bielefeld, are coming slowly to realise the consequences of requiring cycle paths be used (namely, the city assumes some liability) and are relaxing the requirements.

Notice that those are all system-safety issues stemming from road design.

And none of any of that occurs anywhere in the USA as far as I am aware. A couple decades ago, I once walked from a colleague's house in Palo Alto to the California-Street downtown area, a couple miles of suburbs. I encountered *no one else* on the sidewalks the entire journey, until I was in the downtown area. And the walking was uncomfortable because of the configuration of the driveway ramps. Whereas here, people are continually using the sidewalk outside my house to get to and from the bus stop and their houses nearly a kilometer up the road. If I come out just after 6 in the morning to clear overnight snow, there are often already sets of footprints from people walking to the first bus. And I live in a semi-rural village!

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de



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