RT Journal Article SR Electronic T1 Safety in numbers? A new dimension to the bicycle helmet controversy JF Injury Prevention JO Inj Prev FD BMJ Publishing Group Ltd SP 343 OP 344 DO 10.1136/ip.7.4.343-a VO 7 IS 4 A1 C Komanoff YR 2001 UL http://injuryprevention.bmj.com/content/7/4/343.2.abstract AB