While I think of it:
http://dmses.dot.gov/docimages/p75/239101.pdf
Review of the evidence for motorcycle and motorcar
daytime lights
Antonio Perlot
FEMA general secretary
Federation of European Motorcyclists' Associations
Stephen Prower
BMF research officer
British Motorcyclists Federation
7 March 2003
Summary
The paper reveals the defects of method, conduct or findings of Janoff et al 1970, Andersson et al 1976 and the other main monitoring studies to date of the effect of motorcycle and motorcar daytime light laws. It weighs up the prima facie arguments for and against motorcycle and motorcar daytime lights, and predicts that on balance motorcar daytime lights may manifest a net safety disbenefit. It approves the method of Olson et al 1981's motorcycle gap acceptance experiment, but notes the limited import of the findings. It finally canvasses how ostensible motorcycle ‘conspicuity’ accidents that in fact have other causes can be prevented.
Longer, final, version:
8. Summary and conclusions
The purpose of this paper has been:
• To review the evidence in favour of both motorcycle and motorcar daytime lights
• To consider in the light of the evidence how far the use of daytime lights by motorcars as well as motorcycles is likely to enhance overall road safety
• To review some of the other remedies for motorcycle accidents that compete for attention with the use of daytime lights.
In conclusion the formal evidence of the monitoring studies of the effect of both motorcycle and motorcar daytime lights fails to establish satisfactorily that daytime lights have had any overall effect to reduce accidents. The methods that the studies have employed are inherently flawed: the odds-ratio method is not specific to the effect of daytime lights, and the fleet study method is incapable of distinguishing between the immediate ‘novelty’ effect of daytime lights, and their enduring true effect.
The prima facie arguments in favour of motorcar daytime lights in turn fail to ‘rescue’ the studies. On the positive side of the balance, the effect of daytime lights to reduce accidents is likely to be trivial. On the negative side there are important potential adverse side-effects.
The situation of motorcycle daytime lights is similar, save that there is more to be weighed in their favour on the positive side of the balance. Experimental field studies might assist to carry matters forward. The uthors know of only one important study: the motorcycle study Olson et al 1979a.
Encouragingly, Olson et al made findings that—although they were specific to the prevailing situation in Michigan in the late 1970s—suggested that motorcycle daytime lights might have a positive beneficial effect.
On the other hand Olson speaking informally to Despain 1981, and
later also Olson 1989 cautioned that ‘conspicuity treatments’ might not treat all of the causes of motorcycle accidents at intersections.
Against this background in 2001 the European motorcar manufacturers
and importers offered to the institutions of the European Union to hard-wire all of their production of motorcars for the European market from 2002 with the headlights permanently on.
At the same time the European motorcycle manufacturers and importers decided also to ‘hard-wire’ all of their production of motorcycles for the European market.
Given that, on the evidence of the study findings and arguments, it is unlikely that motorcar daytime lights confer any positive ‘net safety benefit’—indeed it is possible that they may even manifest a negative safety disbenefit—, the offer of the motorcar manufacturers is misguided. Further it is likely that motorcar daytime lights will diminish the positive safety benefit that, it is less controversially asserted, motorcycle daytime lights confer upon motorcycles. The offer of the European motorcar manufacturers should therefore be unequivocally rejected.
The authors pass over the unfortunate revival, by the decision of the motorcycle manufacturers, of the bitter controversy that has divided motorcyclists and motorcyclist's organisations in different countries over the past thirty years whether governments should override the objections of the section of motorcyclists who oppose daytime lights by legislating to make motorcycle daytime lights compulsory.
Instead the authors take up from the cautions against a blind belief in the efficacy of motorcycle daytime lights that were uttered by Olson 1989 — they list, drawing inter alia upon the suggestions of Olson's paper, a number of causes, or possible causes, of motorcycle accidents at intersections (or motorcycle accidents with a pedestrian) that motorcycle daytime lights do not, or will not, prevent — and in the spirit of moving forward they canvass research needs and the potential that also exists for devising new means of prevention.
The authors conclude by recommending the prompt conduct, in the interest of the safety of motorcyclists, of the research in question.
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