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Mobility & Transport - Road Safety




What is kinetic energy?

Kinetic energy is the energy that is built up by movement of an object. The faster the movement and the heavier the object, the more energy is built up. The formula for kinetic energy (Ek) is:

Ek = 1/2* m* v2

with m is mass and v is speed.

Hence, a moving vehicle builds up kinetic energy. In case of a collision the energy must somehow flow away. The two objects involved in the collision will have to absorb it.

What is Sustainable Safety?

Sustainable safety is the road safety vision of the Netherlands. It was launched at the beginning of the 1990s and accepted as a formal part of Dutch policies in the mid 1990s. As summarised by Wegman et al. (2005, page 1)

"the Sustainable Safe vision is based on two leading ideas: how to prevent human errors as far as possible, and how to ensure that the crash conditions are such that the human tolerance is not exceeded and severe injury is practically excluded. The starting point of 'sustainable safety' was to drastically reduce the probability of crashes in advance through safety conscious planning and design. Where traffic crashes still occur, the process that determines the severity of these crashes should be influenced, so that serious injury is virtually excluded. Within sustainable safety, man is the reference standard (human error and human tolerance). A sustainable safe traffic system has an infrastructure that is adapted to the capabilities and limitations of humans through proper planning and road design, has vehicles that are equipped to simplify the driving task and offer protection to the vulnerable human being (crash protection), and finally, has road users that are properly educated and informed, and which driving behaviour is regularly controlled. The key-issue of 'sustainable safety' is that it has a preventative rather than a curative (reactive) nature."

What is a regression-to-the-mean effect?

"regression-to-the-mean denotes the tendency for an abnormally high number of accidents to return to values closer to the long term mean; conversely abnormally low numbers of accidents tend to be succeeded by higher numbers. Regression-to-the-mean occurs as a result of random fluctuation in the recorded number of accidents around the long-term expected number of accidents. Regression-to-the-mean threatens the validity of before-and-after studies, but is, at least in large samples, perhaps a less serious threat to validity in cross-sectional studies."

Regression-to-the-mean is particularly likely to occur if locations for safety measures, such as speed enforcement, are selected on the basis of their bad accident record, as is normally the case. This means that evaluation studies must take account of the likely regression-to-the-mean effect to get a reliable estimate of the effectiveness [20].

What is the SARTRE study?

SARTRE is an acronym for 'Social Attitudes to Road Traffic Risk in Europe'. The SARTRE study is funded by the EU and participating countries and aims to study the opinions and reported behaviours of car drivers throughout Europe. The study applies questionnaires that are presented to the respondents in face-to-face interviews. To date three surveys have been performed. The first one was in 1991-1992 (15 countries); the second one in 1996-1997 (19 countries); and the third one in 2002-2003 (23 countries). More information is available at