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Does increasing intrigue and uncertainty
compromise safety?
In this section I will explore three key propositions that form the
basis on a new understanding of the connections between unpredictability
and safety. At first glance it would appear that there is a paradox when it comes to safety: you can make an environment safer by making it more predictable or in some circumstances, you can make it safer by making it less predictable. The rubber-necking phenomena (where people looking at an accident, lose concentration and have an accident themselves) is largely a problem that happens on freeways or major roads that are designed for maximum through-put of vehicles. The design rationale for these kind of roads has been to remove all unpredictability and make them as predictable as possible. In many cases even the last elements of intrigue have been removed by segregating the road from the surroundings with noise barriers. Through the design we are making a covert promise to motorists: 'This is a predictable environment in which you are highly unlikely to encounter the unpredictable'. The motorists therefore drive according to these perceptions. On a whole, removing the unpredictable from this environment does make it safer. However, if the motorist is suddenly confronted with the unpredictable or an element of intrigue (such as an accident, or a stray animal), they are in the wrong head-space to deal with this. Their senses are not on high alert and they are travelling too fast to deal with this unexpected distraction. There is therefore a downside to this strategy of trying to improve safety by making an environment totally predictable. While ever there are humans involved, it is impossible to deliver the promise of total predictability. The designer has therefore created a false sense of security. By contrast, if a motorist is driving down a residential street and sees children's toys on the side of the street, or kids playing in the street, the visual clues say 'this is a space in which the unexpected should be expected'. The motorist immediately slows down to accommodate the possibility of the unexpected happening. This does not mean they adjust their speed to a level that eliminates all risk. (The same people who take unacceptable risks on the freeway will take unacceptable risks in a residential street full of children.) The truth is that we all add a certain 'risk factor' to what we perceive to be 'safe'. Make our vehicle or travel environment 'safer' and we will travel faster (we add the same amount of risk to the new safety level). But the opposite is also true. Make our travel environment feel less predictable and we will travel slower. We will still be taking the same amount of risk as before, but we will be going slower. Because we are adding the same amount of risk factor as before, we will have (on average) about the same number of 'accidents'. However, because the speed is slower the accidents are likely to be less severe. All motorists drive according to their perceptions about risk levels. For example, in places that have snow and ice in the winter, reported accident rates often go down because drivers modify their behavior in accordance to their perception that risk levels have risen dramatically. Proposition 2: Safety is maximized when perceived risk is equal to, or higher than actual risk. Clearly it is not the amount of predictability or unpredictability that makes an environment safe or unsafe. Any environment becomes unsafe if the actual risks are higher that the perceived risks - that is, when drivers are lulled into a false sense of security about the degree of danger present. This proposition is best illustrated with a story. Over the past few years I have conducted dozens of 'instant street reclaiming' events in neighborhoods around the world. In these events we demonstrate how neighborhood activity and neighborhood created devices can dramatically slow traffic. We never close the street to traffic, put up barricades, or use official warning signs for these events. The rationale is quite simple. We are demonstrating how neighborhood activity and car movement can coexist spontaneously in the same space (in the past, when kids played in the street, they did not have to put up official warning signs). One of the things I learned very early from these events was that having no official warning signs actually made these events safer. Motorists see some unexpected activity in the street up ahead and a million questions start running through their head. 'What is happening? Is there an accident or is it a party? Am I allowed to proceed?' They immediately slow down so they can take in as many visual clues as possible to decipher what is going on. Because there are no signs that spell out for the driver what is happening, they become absorbed in the task of working out what is happening. Usually by the time they get to the actual activity zone they are going at a snails pace and inevitably stop to ask what is happening. A sign that said 'Warning, Street Party Ahead' would preempt both the intrigue and uncertainty factors. Once the questions have been answered, they can get back to what they were doing before, going somewhere as fast as possible. In one city we had a dramatic illustration of why intrigue and uncertainty can help make an environment safer. The city engineer insisted that for the instant street reclaiming event we put 271 red traffic cones down the center of the street and erect half a dozen official warning signs. Traffic would use one half the street and the residents would do the street reclaiming on the other half. It was without doubt the most dangerous street event I have ever conducted. The traffic devices told the motorists they could be certain what was their space. It was a promise of predictability and certainty. So they speed down the corridor reserved as their exclusive space. Yet this promise of certainty and predictability was a totally false promise. Just a few meters from the speeding traffic were children playing with bikes and balls. What made the event unsafe was not that kids were playing with balls in a street. We had done that many times before in complete safety. What made the event so unsafe were the false messages about predictability conveyed by the cones and signs. The motorist was promised a level of predictability that did not match the actual risk levels. If the 'normative state' of a street is that the unexpected should be expected, then all of the visual clues must point in this direction. In establishing clear signals about the normative state of a street, what is not included is often more important that what is. If the normative state is that the unexpected should be expected, then traffic control devices such as line markings, official signage, concrete islands and even first-generation traffic calming devices create a mixed message. They promise certain levels of predictability. Ambiguity and lack of clear direction can be incredibly important visual clues as to the 'normative state' of a space. (More about this later.) To be a little technical, safety is determined, in part, by the Perceptual
Actual Differential (PAD) Factor, that is the actual risk minus the
perceived risk -- popularly called 'false sense of security.' Depending
on the design clues, the PAD factor may be higher in a highly predictable
environment than in a highly unpredictable environment, and vise versa.
The actual degree of predictability/unpredictability has nothing to
do with whether a motorist has a false sense of security. ( Let me take a slight diversion to address a very important issue about false sense of security (one which helps us understand the dynamics a little better). Many city officials have begun reducing the number of pedestrian crossings on the basis that they engender a false sense of security in the pedestrian, which leads to higher accident rates. While this is true to some extent, the same officials are not removing traffic control devices across the city because they engender a false sense of security in the motorist. The pedestrian crossing debate has been a classic case of blame the victim. No accident at a pedestrian crossing, where the pedestrian is obeying the law, should be blamed on the pedestrian, regardless of whether they are feeling a 'false sense of security' or not. It is the motorist who is not taking due care, and this is partly because the motorist has already been lulled into a false sense of security before they get to the pedestrian crossing. And the motorist's false sense of security has been engendered by the fact that there are not enough design signals that pedestrians are present. (We will show later that these design signals should probably be something other than a standardized crossing.) Simply removing the pedestrian crossing and forcing the pedestrian to increase their level of vigilance while doing nothing to increase the vigilance of the driver is a grossly unjust way to tackle pedestrian crossing deaths. In fact the current policy of removing crossings is totally counterproductive when you consider the big picture. It actually promises the driver greater levels of predictability by removing any visual clues about the presence of pedestrians (which are already too scant). While removing the crossing diminishes the pedestrians PAD or false sense of security it increases the drivers PAD even further. We will now expand the safety picture and explore a number of factors
that determine the overall risk of death or injury that a person exposes
themselves to when driving. Then we will see how all the factors work
in concert. The total danger that a particular person is exposed to is a combination
of all the above factors. For the mathematically minded, my hypothesis
is this: This means that in terms of safety, there are a number of things that an authority can do to make environments safer: — Reduce PAD (or false sense of security) by having the design of an environment signal to the driver that they are likely to encounter high levels of unpredictability. The greater the level of unpredictability likely to be encountered, the greater the ambiguity required in the design. — Promote such high levels of human activity that the intrigue and uncertainty generated by the activity 'swamp' contrary design signals. — Reduce the propensity to take risk through education and social programs. As we will describe later, behavior modification programs can reduce people's propensity to add risk. — Add new risk factors and increase perceptions of these 'risks' e.g. installing red light cameras and running a public education campaign about them adds a financial risk to the already existing safety risk of running red lights. — Teach people how to mitigate or compensate for the risk imposed by others (e.g. Defensive Driving Courses or cycling classes for students). — Bring speeds down by introducing new elements of intrigue and uncertainty and/or by reducing the design speed of the environment and vehicle. Proposition 3. Community vision, not design criterion, must determine the amount of intrigue and uncertainty built into a space It is true that under certain conditions it is possible to make an environment safer by making it more predictable. However, it is equally true that one can make other environments safer by increasing uncertainty. The key to safety is to reduce the differential between actual and perceived risk. There is no doubt that you make a freeway safer by reducing elements of uncertainty because this reduces the gap between the certainty promised and the certainty delivered. Theoretically it is also possible to make city residential streets safer by making them more predictable. However, unless we also reduce the number of spontaneous events that the motorists may be exposed to, all we have done is create a false sense of security which diminishes safety. The question therefore becomes whether it is socially acceptable to reduce the spontaneous events that the motorist is exposed to. For thousands of years, streets have not just been a place for moment, but also the stage for spontaneous neighborhood-building activity and the market place for commerce. In the book Street Reclaiming I explored how these spontaneous activities form the very essence of vibrant cities. The health of any city can be judged by the health of its 'spontaneous exchange realm' - the amount of 'good things' we get accidentally as we move through public space. By very definition, these spontaneous exchanges have high levels of intrigue and are totally unpredictable. So cities that are working to increase the vitality and health of their neighborhoods, at the same time as they are making the design of their streets more predictable are working at cross-purposes. They end up with the worst of both worlds: diminished neighborhood life and unsafe streets. Vibrant neighborhoods PLUS safe streets EQUALS high levels of ambiguity in the street design. Design of a traffic environment can be a self-fulfilling prophecy.
Create a traffic environment that encourages speed and domination by
cars by increasing predictability and community life will retreat from
this space which further increases predictability. On the other hand,
create a traffic environment with high levels of ambiguity and traffic
speeds will drop and community life will blossom in this space, resulting
in an increase in unpredictability. ( So should there be any spaces that are highly predictable and primarily for movement? (By very definition, spontaneous community life must be minimized in these spaces.) The ancient art of city building understood that to create an efficient city, they must minimize the amount of space devoted purely to movement. This lesson was learnt from how space is arranged in buildings. The more space dedicated purely to movement (corridors) the less efficient the building. The art of city building has not changed. |
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 Related articles: Street Reclaiming Introduction Street Reclaiming though activity Instant street reclaiming event Integrating 2nd Generation Traffic Calming into an existing traffic calming program
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