RESEARCH - Safer speeds: an evaluation of public education materials

Speed DemonChoosing the speed to drive at on our highways is a highly controversial and individual decision. I would dare to say that the posted speed limit is only a guide for many drivers. For those drivers, the choice ranges from total disregard to the point that you decide what is 10 over from. Even some police managers that I have worked for over the years tended to downplay the involvement of speed in our collision problem. Personally, I remain convinced that those who consciously decide not to follow the rules are a part of the problem and civil disobedience has no place on our highways.


How to we educate drivers so that they will choose to follow the speed rules? The Centre for Automotive Safety Research at the University of Adelaide, Australia asked that question in the publication Safer speeds: an evaluation of public education materials. Of particular interest to me was the section starting at page 19 that examines the rationalizations for speeding and how they might be countered.


Safer speeds: an evaluation of public education materials (PDF)

I read the paper you referenced and found that one of the sources given was to Nilsson's Power Model (2004).  This paper was evaluated and refined in a report by The Institute for Transport Economics, entitled: Speed and road accidents An evaluation of the power model, by Rune Elvik, Peter Christensen, and Asrid Amundsen.  They took the original formula given by Nilsson  I believe the original paper by Nilsson gave a general formula for all accidents, whereas the second paper broke down the data a gave a formula for each type of accident. The reduction in the number of accidents for even a slight reduction in speed is truly astounding.

I used the formulas give and calculated the difference in the number of accidents when speed is reduced from 50 kph to 40 kph and then to 30 kph.  For every 100 accidents at 50 kph the corresponding number is given at 40 and 30 kph.  I will try to copy those calculations here.  I hope it works:


Accident or Injury Severity Exponent 50 kph 40 kph 30 kph
Fatalities 4.5 100 37 10
Seriously injured road user 3.0 100 51 22
Slightly injured road user 1.5 100 72 46
All injured road users (severity not stated) 2.7 100 55 25
Fatal accidents 3.6 100 45 16
Serious injury accidents 2.4 100 59 29
Slight injury accidents 1.2 100 77 54
All injury accidents (severity not stated) 2.0 100 64 36
Property-damage-only accidents 1.0 100 80 60


Our safety group here in Saanich, Community Advocates for Reduced Speed is working hard to educate our local politicians about the need and indeed numerous benefits of lowering the speed limit on residential streets.  It is tedious work, mostly because they really don't want to know.