[I’ve had this sitting in draft for months, so I’ll publish as is, and maybe come back to edit later with anything else that comes to mind. It was drafted with Indipac top of mind, but most of it (bar the UHF radio) applies to all touring, and for that matter, pretty much any road riding. I would personally even put in a plug for even cyclepath/shared path riders to have a mirror, because people weaving all over the place with no clue what’s coming behind drive you crazy!]

Lights
We run rear red flashing lights, even during the day, and a white light on the front – flashing during daylight.
On Indipac we ran three rear lights.

Mirrors
We use the standard/original length Take A Look mirrors mounted on our glasses, and have done so for years now. We feel incredibly unsafe riding without them now – the feeling is akin to driving without a rearview or side mirror. Whenever we ride in a group it is very noticeable that those of us with these mirrors are the ones calling out about any traffic approaching from behind. Being able to turn your head side to side gives flexibility of vision, even being able to scan the road behind the opposite shoulder (very useful for being aware of merging traffic.)

They are available for left or right mounting depending on which country you are riding in. Don’t let any vendor tell you to just use it on the other side but in ‘portrait’ mode. (Yes, this happened to us once with an Australian online vendor, who sent us left mount mirrors and then argued the point with us.)

What about helmet mirrors? I lost my Take A Look in the middle of a tour once and picked up one at the nearest LBS that attaches to a helmet. I didn’t like it as much – and I bumped it out of adjustment every time I took my helmet off. And adhesive on a helmet is not great.
Stick to the ones that mount on the glasses. I carry a spare now.

They are dependent on good vision in the eye closest to the mirror. We bought left-side mount mirrors for our US tour and I was unable to use mine as I am short-sighted in my left eye. (Using my right-side mounted one was still waaaaay better than none at all.) It took Marc a little while to get used to it (much like getting used to driving on the other side of the road to what you normally do and having to change the habit

Here’s a good article about why mirrors are essential for safety.

Bright clothing
There’s a popular argument that fights back against the ‘blame the victim’ mentality in regard to putting the onus on cyclists to be seen. I take the point, but people – in cars – are fallible. They should be more aware of cyclists, but the reality is they’re not. And you can’t argue that they should have seen you if they were alert if you are dead. We have enough to deal with in car-driver attitude even when they can see you.
Bright helmet too. It can only help.

Reflective stuff
Anything you can. Reflective vest at night/early mornings. Our frame bags were made with reflective tape, and our tyres had a reflective strip on the wall.

UHF radio
Absolute essential for the first half of Indipac – across Great Eastern Hwy, the Nullarbor and Eyre Highway. (I’ve detailed during the Indipac blog posts the sort of stuff I settled on saying. )