The cyclists these days have terrible manners. Bicycle accidents could potentially hurt people's lives, but they're not very aware of this danger.
ご質問ありがとうございます。
"The cyclists these days have terrible manners."=「最近、自転車を乗る人達は酷いマナーである。」
"Bicycle accidents could potentially hurt people's lives,"=「自転車事故は人々の人生を傷つける可能性がある」
"but they're not very aware of this danger."=「でも、彼らはその危険についてあまり意識していない。」
ご参考までに。