Do traffic lights make intersections safer?

Before-and-after studies show that intersections become safer after implementation of traffic lights [17] [18]. However, when the number of injury crashes at signalised intersections is compared to this number at other intersection types with similar traffic volumes, signalised intersections are the least safe intersection type. Unsignalised intersections and roundabouts have fewer injury crashes [9] [19]. So, after adjusting for traffic flow to determine risk, signalised intersections are still less safe.

In addition: traffic lights are often used when the number of passing motor vehicles is too high for other intersection types to cope with. They enhance traffic flow.