Are LEDs in modern streetlights usually pulsed? If so, roughly what frequency?
LEDs used for street lighting usually employ a DC/DC converter of some kind, with tight current control at its output. So, providing a steady current isn't reducing efficiency nor does it add unnecessary components which could fail, nor does it reduce the lifetime of the LEDs.

It's the simplest and most efficient way to drive a high-power LED array. Steady current, provided from a "pulsed" source.