From the recently released CHP lane splitting "guidelines" ( http://www.chp.ca.gov/programs/lanesplitguide.html ):
- At just 20 mph, in the 1 or 2 seconds it takes a rider to identify a hazard, that rider will travel approximately 30 to 60 feet before even starting to take evasive action. Actual reaction (braking or swerving) will take additional time and distance.
I believe this is fairly accurate. Combine this with the amazing ability cars have to swerve in the worst possible direction at the last second and I think that does make lane splitting more dangerous than moving at the speed of traffic. In stopped traffic I also believe sitting behind a car is asking to be rear ended. These all fall into the dangers of riding a motorcycle in general, and I don't believe they are dramatically riskier than driving a car. I tend to ride just above the speed of traffic and I lane split and I commute approx 80 miles a day four days a week. So far in my mind this seems to be the safest way to ride, combined with choosing a route with the least traffic. Every time I lane split I recognize the possibility of a car jumping out directly in front of me in a situation where I have nowhere to go and no time to stop. I guess that's on par with being rear ended as it's usually from a driver who is paying no attention and not looking in their mirrors before they change lanes.
I agree that cellphones are a huge cause of distracted driving and accidents, but I think they are in a different class from seatbelts. While cellphones may cause more accidents, seatbelts are a limiter of damages in an accident, very similar to wearing a helmet on a motorcycle and the statistics really back it up. Just googling a random study (ironically one about the dangers of airbags) gave a 67% reduction in fatalities from seatbelt usage. Airbags generally seem to help, but also cause damage at low speeds and need refinement. The other big factor in modern cars are their crumple zones. Wearing seatbelts combined with the crumple zones has allowed people to walk away from accidents that in the past would have been guaranteed deadly. No seatbelt, and you typically get hurled out a window and thrown to the pavement at whatever speed you were travelling (imagine getting tossed out of a building from 50 yards up). I have been pulling people out of wrecked cars for about 10 years now and usually the dead ones were the ones with no seatbelt on.