Wear a helmet on a motorcycle or e-bike, and fasten the strap

High value
Evidence A
Buys life
Costs a little
Takes minutes
No willpower

In plain words

Wearing a helmet with the strap fastened lowers a motorcyclist's risk of dying in a crash by about 40%, and of a head injury by about 70%. The strap has to be snug — a helmet dangling loosely on your head doesn't count.

Cost: A helmet costs 100 to 300 CNY. 5 seconds to put it on each time.
What you get: Cochrane pooled several studies. For motorcycle riders, wearing a helmet lowered the risk of death by 42% (odds ratio OR 0.58; 95% CI 0.50 to 0.68, the plausible range). Head injuries fell by 69% (OR 0.31, 95% CI 0.25 to 0.38)
Notes: Fasten the strap; a helmet hanging on the handlebar doesn't count. The numbers above come from motorcycles. There are no direct studies on e-bikes; the figures are carried over because the head is hurt the same way in a crash.
Evidence grade: A : Specific numbers from meta-analyses, large cohorts or randomized trials; for law and policy, the statute or official text.
Sources: Liu BC 等 (2008). Helmets for preventing injury in motorcycle riders. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.CD004333.pub3

Translated from the Chinese original. Original book, section 1, tip 2. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer