There were lots of people ignoring the traffic light.
There were many people jaywalking.
There were many people running the red light.
「信号無視が多かった」は英語で「There were lots of people ignoring the traffic light.」と言います。歩行者が信号を無視したら「jaywalking」といい、運転している人なら「running a red light」と言います。
信号無視が多かったから危なかった。
There were many people running the red light which was dangerous.
My friend went through several red lights when we were driving around Tokyo.
I was standing at an intersection in a busy part of Tokyo, and I saw several cars go right through a red light.
詳しい状況がわかりませんが、次のような言い方をすると良いでしょう。
ーMy friend went through several red lights when we were driving around Tokyo.
「友達と東京周辺をドライブした時、友達は数回信号無視をした」
to go through several red lights で「幾つかの赤信号を通過する」＝「信号無視をする」と言えます。
ーI was standing at an intersection in a busy part of Tokyo, and I saw several cars go right through a red light.
「東京の混雑したエリアの交差点で立っていたら、信号無視をした車を何台も見た」
intersection で「交差点」
to see several cars go right through a red light で「信号無視をする車を何台も見かける」
ご参考まで！
カナダ 
