Dear Editor, Bruce Todd tells us that "the economic impact of even one head injury is enormous, and it's a cost we can help curtail as a community if all cyclists wear helmets" [“Bicyclists Collide in Helmet Law Debate,” News, Aug. 4]. By this measure both motor-vehicle passengers and pedestrians should also wear helmets, since both these groups have considerably larger numbers of head injuries than bicyclists. According to the CDC, 20% of all head injuries are caused by motor-vehicle crashes, only 3% by bicycles (www.cdc.gov/ncipc/tbi/Causes.htm). Per hour, driving is almost twice as deadly as bicycling and at least as likely to cause a serious head injury (www.magma.ca/~ocbc/comparat.html). Last year there were more than 2.5 million injuries due to motor vehicles, and the cost of motor-vehicle accidents is around $10 billion per year in Texas alone. Given the extraordinary cost to society, I might reluctantly be willing to accept a mandatory helmet law for occupants of four-wheel passenger motor vehicles. Bicycle helmets are another matter entirely. Any manufacturer will tell you that bicycle helmets are only effective at very low speeds (less than 14mph) on flat surfaces. Any deviation from this, and a bicycle helmet can actually increase the severity of injury (www.cyclehelmets.org/papers/c2023.pdf). This would explain why head injuries have actually increased at the same time that more bicyclists are voluntarily wearing helmets (www.bicycleuniverse.info/eqp/helmets-nyt.html). The only purpose a bicycle-helmet law would serve would be to criminalize transportation bicycling for many bicyclists. I readily acknowledge that I'm a yellow rat bastard for choosing a form of transportation that doesn't pollute, doesn't add to congestion, doesn't endanger other roadway users, and doesn't help finance international terrorism. Asking City Council to pass an ordinance making me a criminal for riding a bicycle without a piece of Styrofoam strapped to my skull is, however, taking matters a bit too far.