Weekend before last, a CalTrans dumptruck...with a snowplow on the front, was trundling along the median where some contruction was underway, and I'll be damned, but it had some sort of rearward-facing Ka band emmitters. Surprised me, as we'd just been booking along nicely, though the dudes in the new S-class AMG and 5-series BMW were a good 3/8 of a mile ahead of me, so no worries. My wife's '02 AWD RX300 has a govenor @ 110, FWIW. Probably as fast as you'd want to travel in that machine, if not because of handling issues (or lack thereof), because of massive fuel ingestion. However, it is remarkably quiet, especially given it's frontal area.
Is this some kinda backup warning device which is always 'on'?