Please, please - cycling in poor weather or in the dark without lights or reflective kit is an invitation to disaster. I've seen too many cyclists (mostly young men) with dark clothes and no reflectors or lights - drivers have to be particularly alert to see dark cyclists --- add in some rain and distraction from other traffic or a mobile phone :( --- and disaster awaits!
Items which move while cyclists are pedalling are excellent to attract attention - for instance hi-viz leg bands with velcro tabs that keep your trousers from getting stuck in the chain
Hi-viz vests offer 360 degree visibility - I use the make in the following link - have washed it several times and it still works well after three years.
The best safety measure is to mount front and rear lights. There is wide choice between self-generating dynamos, LED blinking attention grabbers and so-called ABS systems for 'Blair Witch' lighting on off-road paths. See the following link for more details:
My favs are dynamo-driven front and rear lights - good for commuting and night riding on well-lit urban roads, and the Niterider ABS system for jaunts on dark tow paths. The advanced systems are more expensive but the batteries can be recharged hundreds of times and these are the only lighting systems that provide safe see-and-be-seen lighting where there are no streetlights (or a new moon). See the following link: