Here’s a quick tip.
If you’ve got a Prius with radar cruise control then you may find under certain conditions that it will disengage and flash up an error saying “cruise control not available”. You could be forgiven for thinking that there may be a computer fault with the vehicle but there is another situation that causes this to occur.
The radar cruise control is tied in with the automatic windscreen wipers and when the windscreen sensors detect enough rain to necessitate the wipers to operate at their maximum speed this automatically disengages the radar cruise control. This is a safety feature as too much rain can impede the ability of the radar to reliably and accurately detect vehicles in front of you.
However, at your own peril, you can disengage the automatic wipers and change the setting to something other than the HI setting which will allow the use of the radar cruise control once again irrespective of the actual rain conditions. Probably not the best thing to do though.