They make people on the main road slow down, which is a feature, not a bug. What you mean is that they're the most efficient at what they do when the traffic is

They make people on the main road slow down, which is a feature, not a bug. What you mean is that they're the most efficient at what they do when the traffic is comparable. They only reduce accident at the expense of a slightly lowered throughput if the traffic is highly disparate.