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UK Road Sense, Dorset Way / A3049 50 limit

Fleetsbridge Roundabout Traffic lights - a proper analysis - traffic lights probably INCREASED accidents



  1. There is not enough information to be certain about anything, other than one thing: to claim that the lights have reduced accidents from 7 to 2.68 (which seems to be the ONLY justification from Poole Council) is clearly complete nonsense:

-         Event rates are low, random variations high

-         Important factors such as traffic volumes / distributions, general trends, changes in reporting, have not been considered

-         Other changes at the roundabout (road markings, effects on journeys by changes at the many nearby large stores), etc have not been considered

  1. However, if we are to believe that the accident counts have been influenced predominantly by the traffic lights, one thing (only) sticks out like a sore thumb: if you include the few years of data PRIOR to the original installation of the lights, the original installation (full time) in June 93 saw an INCREASE and when the lights were switched to part time in Nov 95 accident counts increased again significantly. Obviously, comparing 2 periods with 7 years between them when many things have changed is a lot less reliable than comparing the 3 years directly before and after - and this shows an increase.
  2. When the lights were switched back to full time from Nov 2000, accidents did fall significantly – but ONLY back to levels that might have been expected anyway if the lights had never been there (as illustrated by the curve). And you can reduce accident counts in one area by reducing flow, but those accidents will probably just happen somewhere else.
  3. The minimal reductions seen could probably be achieved just by reducing flow by some other means, reducing number of  / widening lanes, etc, a bit of paint instead of expensive traffic lights that cost drivers and the environment 24 hours a day. This would not reduce flow at all when traffic is light and would limit flow, vehicle density, make it easier to join leave the roundabout etc thus reducing collisions when busy. 
  4. There are other ways to reduce accidents: proper policing would be the most effective way. Even if the lights have reduced accidents, it does not mean it is the most cost effective and efficient way of doing it. All options should be properly considered.
  5. So a proper analysis using all available data and looking at the wider picture can only conclude that the overall “experiment” to install traffic lights on this roundabout has caused more accidents than it has prevented, not to mention all of the congestion, pollution, wasted time and fuel for thousands of drivers every day.
  6. Even despite the uncertainties mentioned in 1 above, the accident increase during part time operation looks undeniable. This surprises even me, perhaps there is an explanation for this, maybe the presence of lights gives drivers a false sense of security, without the control if they are switched off. Perhaps speed limits / humps / loads of road signs etc. have the same effect. Perhaps it is better to allow drivers to think a bit more about their driving rather than blindly following increasing numbers of rules and control that seem to have no reason (but can of course generate revenue).
  7.  So, reassuringly, a proper analysis supports common sense: it’s a roundabout, it does not need traffic lights to improve safety OR help with traffic flow.
  8. It is truly worrying that our “experts” can get things so completely wrong, and draw the conclusions they want, to do what they want, by such naïve and simplistic interpretation of data. And these are the same “experts” presumably who are deciding on new town bridges, road safety, speed limit reductions, other road “improvements”, etc. No wonder we’re in such a mess. When are things going to change in Poole / Bournemouth / Dorset?
  9. The best course of action now at Fleetsbridge is to simply remove the new traffic lights and sell them for scrap, and to learn from the failure and to not repeat it. Please can Poole Council do this or provide a proper scientific justification for the lights.