However, the penny farthing's popularity lasted only about 20 years, until the advent of the safetybicycle.
不过，随着安全自行车的出现，这种车子只流行了大约20年。
2
Mariah Nunes, a sophomore who is a team manager, said she researched an essay on bicyclesafety.
校队经理同时也是大二的玛丽亚·纽恩斯说她在研究一篇有关自行车安全的论文。
3
In some parts of the world, cyclists have been powering safety lights for years with devices called bicycle dynamos, which use a generator to create alternating current with every turn of the wheels.