This is the dry bit where the claims that are made by Wrongheaded are documented.
If you’re looking for further reading, we highly recommend the influential Bicycle Helmet Research Foundation, who have many excellent and approachable articles for readers of both a technical and non-technical background.
1. “There were no adult cyclist deaths in 2009 or 2010, and there have been no child cyclist deaths in Northern Ireland since 2005.” Mr Poots, Minister for the Environment, during the Cyclists (Protective Headgear) Bill: Second Stage
2. Almost 4000 annual cancer deaths, 3500 from cardiovascular disease and 2000 from respiratory disease – from Deaths in Northern Ireland (2009), NISRA.
3. “Surveys in Edmonton in 2000 (pre-law) and 2004 (post-law) suggest that cycling by children and teenagers has been significantly reduced compared with adults (59% children, 41% teenagers)” – from Helmet laws in Alberta, Bicycle Helmet Research Foundation.
4. “a survey to measure helmet use in 1999 suggested that the cyclist profile had changed, with around 30% fewer cyclists aged 16 to 30 years … and a smaller reduction in the proportion of females cycling.” – from Helmet laws: British Columbia, Bicycle Helmet Research Foundation.
5. “Post-law cycle use fell by 40% to 60%, with the largest decrease among teenagers.” – Chipman R. Hats off (or not?) to helmet legislation, Canadian Medical Association Journal, 2002;166(5): p602
6. “One bike hire company, which had recorded only 2 minor injuries in 100,000 hirings, reported the loss of 90% of its business overnight. Within 6 months of the law, 5 cycle shops went bankrupt and bike sales were down by 70%” – Oz helmet fiasco. Cycling Weekly. 11th December 1993.
7. “Bicycle use by children aged 5-17 decreased by 36% from May/June 1990 to May/June 1991 . There were further falls to May/June 1992 in Melbourne, with teenage cycling showing by then a 46% decrease from pre-law levels .” – from  Cameron, M, Heiman, L, Neiger, D. Evaluation of the bicycle helmet wearing law in Victoria during its first 12 months. Report No. 32, Monash University Accident Research Centre, Melbourne, July 1992 and  Finch, CF, Heiman, L, Neiger, D. Bicycle use and helmet wearing rates in Melbourne, 1987 to 1992: the influence of the helmet wearing law. Monash University, Accident Research Centre report no. 45, February 1993, pp. 35, 36, 43.
8. “A 1994 study by Harrison of school children … showed a 38% decline in cycling from September 1988 to March 1994. This is likely to under-estimate the decline due to the helmets law because cycling is more popular in March than September in southern Australia.” – from Helmet laws: South Australia, Bicycle Helmet Research Foundation.
9. “Cycle trips had fallen by 39% overall, but by 50% for young people aged 5 to 20 years.” – from Hammond L. Pedestrian and cyclist safety in New Zealand. Land Transport NZ.
10. “the current requirement that riders wear a helmet was frightening off many Israelis from commuting to and from work by bicycle, resulting in more people driving – and more traffic, pollution, and accidents” – from Law Would Exempt Adults from Wearing Bike Helmets. Israeli National News
11. The demise of Mexico City’s ill-fated bicycle helmet law – from Mexico City repeals bike helmet law. Copenhagenize.
12. Judge quashes helmet law in New South Wales – from Heady freedom as judge agrees helmet laws are unnecessary. Sydney Sunday Morning Herald.
13. “Clover Moore, Lord Mayor of Sydney, said that she thinks the time is right for a review of compulsory helmet legislation” – from Sydney polls support overturn of helmet law. Sydney Sunday Morning Herald via Bicycle Helmet Research Foundation.
14. “Pedestrians bear a higher fatality rate than cyclists, by a factor of almost 1.5… the belief that cycling is dangerous turns out to be a factoid; opinion based on long repetition, not evidence.” – from Assessing the Actual Risks Faced By Cyclists, Malcolm Wardlow BSc MBA – Traffic Engineering and Control (Dec 2002)
15. An average of 30 seriously injured cyclists per annum – from 2009/10 Reported Injury Road Traffic Collision Statistics, Police Service of Northern Ireland (table 6.9).
18. Half a million years for a cyclist to die – derived from figures in Assessing the Actual Risks Faced By Cyclists, Malcolm Wardlow BSc MBA – Traffic Engineering and Control (Dec 2002).
19. 59% of adults in Northern Ireland clinically overweight or obese, along with 22% of children – Inquiry into Obesity, Committee for Health, Social Services and Public Safety.
20. 69% of car journeys were less than 5 miles – Usage and Monitoring, Sustrans.
21. 10,000 road injury collisions – from 2009/10 Reported Injury Road Traffic Collision Statistics, Police Service of Northern Ireland.
22. “The law resulted in the number of head injuries falling by 11% … cycle use in Western Australia fell by 30%” – from Helmet laws: Western Australia, Bicycle Helmet Research Foundation.
23. Ten years after helmet legislation, the proportion of women cycling to work is still down by 50% – from Commuting trends in Australia, Bicycle Helmet Research Foundation.
24. Letter to Belfast Telegraph, Pat Armstrong, Chairperson, Headway Foyle .
26. Universal cycle helmet use leading to a 10-16% fall in fatal head injuries (a fall in deaths of 3-5%) – from The Potential for Cycle Helmets to Prevent Injury, Transport Research Laboratory.
27. “around two-thirds of [cyclists with fatal head injuries] would have also involved lethal injuries to other parts of the body” – from Cycle Safety Study, CTC.