I disagree with the suggestions for a bright light with a throwy set-up. That Fenix -30 will aggravate drivers if you turn it on 'high' as the beam, while less powerful then a car headlight, is not shaped for on-road use. And even on its most obnoquious setting it may not stop you from being cut-off as drivers beside you won't necessarily see it. While I have an mc-e based light on my handlebars, it is on low for in traffic. The other modes come out when i'm path/trail riding, or in the rain. The main failure of these 'new' lights is that they do not offer a low/mid intensity blinking setting.
To be seen a bright enough blinking light that is visible from a wide angle is best. I highly recommend helmet mounted lights. A blinking red in rear, and a blinking white in front. Ideally these are visible + 180 degrees and at the sides both are visible (too keep you from being T-boned at intersections)
My personal favorite is the MEC turtle lights. They cost $3-$4 depending on single or double emitter. They provide constant on, but best is flashing. Powered by 2 cr2032's, they are bright for ~40hours, are listed as working for 50h but definately last longer just brightness declines. So a few weeks to months depending on how long you ride.
Helmet mount makes all the difference, it puts the light at eye level for SUV's and trucks, and above the taillight level for cars it really makes you stand out.
Each night we go for a ride my partner comments how much room vehicles leave for us. Well marked cyclists seem to be accorded full lane privileges. If you don't find something similar I'll gladly forward you a set, imho it is obligatory cyclist gear.
if you want more, adding a ~100lumen spot to the helmet is great for additon communication with drivers.
I have an MG PLI on my handlebars. I use it on dim usualy for traffic. But this is part of my 'so I can see' set up, and being on CPF that gets just ridiculous.
