My experience in London and NYC is the opposite.

In NYC there was rarely a time that I couldn't hear a siren. I figured it was because of the very long, straight roads with unbroken sight lines and the curious way American emergency vehicles seem to leave the siren on all the time.

In London I live on a main road but only hear them a few times a day, only for a second as they go past, and rarely at night. Quite a lot of emergency vehicles drive past, but they usually have the siren turned off for the small area where they're audible to me.

> In London I live on a main road but only hear them a few times a day

Couple of hundred yards off Old Kent Road and yeah, similar experience - although they do tend to come in bunches around here, it's generally over in a minute or two.

Also have a quite opposite experience. Lived in rural Germany for years and even seeing a police car on the road was something special. You could almost never hear police cars. In all major cities I have been you could hear sirens all day, which also makes sense considering population density etc.