"PBSF" means the Planet Bike SuperFlash.

I worry about my child when she's being driven in a hefty SUV, and in all honesty, I personally would not transport my children in a trailer. I can maneuver pretty quickly in an emergency, but I'm not so sure if I were towing a trailer. Best wishes.

Helmet light with flash/strobe, step up to LiIon rechargeables, beware of glare
 

As others have noted, a helmet light is useful both day and night; if I had to use just one headlight it would be a good helmet light. You can see ahead into turns, more likely to get the attention of cell-phone stupefied motorists, useful while doing repairs, etc.

To put out enough lumens for a daylight headlight/helmet light you probably want to take the jump to rechargeable LiIon cells, either (or both) 18650's and the AA sized (but almost 3x the voltage, so do not use in typical AA light) 14500's plus a good, safe charger.

The general consensus on the Electronics subforum is that LiIon flashlights are the best lumens/dollar. The best charger (short of hobby chargers) is Pila's, but not inexpensive (it will charge both 18650's and 14500's). There are lower cost ones (see the Electronics subforum). Helmet mount the light with the Zefal DooDad, TwoFish BikeBlock or TwoFish LockBlock, depending upon your helmet's vent configuration.

Current favorites of the day & night cyclists in our family are the UniqueFire G10 CREE XP-G R5 6-Mode 350-Lumen White LED Flashlight (no, its not really 350 lumens but it is bright and has both a fast ~10 Hz and slow ~1.6 Hz flash rate) on the helmet and the MG P-Rocket Cree XP-G R5 450+ Lumens Compact LED Flashlight "OP Reflector" on the handlebars (no flash mode, though). Perhaps even better (latest LED generation) would be the one of ShiningBeam's lights using the Cree XM-L T5 LED.

If you are experiencing more close calls now, as previous poster notes, the sun is now low on the horizon for more of the day in northern latitudes, so glare is much more of a hazard than in summer. Remember the direction you cast a long shadow is the direction approaching motor vehicles may not see you due to glare.

I on the other hand have no reservations about transporting my children in a trailer. Cars give me more room when I have a trailer, and I'm more visible. I have a slow moving vehicle triangle mounted about chest height on the trailer that adds daytime and nighttime visibility.

I have a tandem that my older son rides on with me or my wife, and the Trail-A-Bike that I use with my daughter, as she is almost too big for the carrier.

I'm fighting my protective instinct half the time, but my logical mind usually wins and I put the bubble wrap back on the shelf for another day. I try to remember everything I did as a kid and wonder if I would be a wuss if I hadn't done those things. That's usually what makes me let my kids do things, even though I want to protect them.

Helmet lights are really good at preventing drivers from pulling out or turning in front of you. I've got a Fenix LED flashlight mounted on my helmet, and it really helps visibility in traffic. When I see a car ahead in a sidestreet or parking lot, I just turn my head toward them briefly and they get a quick shot of 100+ lumens, which gets their attention. Haven't had anyone pull out in front of me since I put the light on my helmet.

Also, you say you wear visible clothes, but how visible? Screaming yellow, neon yellow-green is the most visible color -- far better than red, orange and other options. I usually wear neon yellow jerseys, vests or jackets when it's dark as well as some ankle bands in the same color.

My guess is that nothing works in daylight. Car with two bright "day running" headlights get involved in accidents during the day all the time.

If you look at the picture 10 Wheels posted, that headlight blends in pretty well. Unless you were focused on it, you'd never notice it.

Maybe some very bright flashing lights - as in "as bright as auto headlights" and flashing might work. But I don't know if there are any bike lights that are really as bright as auto headlights (despite somewhat optimistic manufacturers claims).

Utility trucks around here do use some kind of very bright strobe light mounted in/very close to turn signals. Those are bright enough to catch my attention in daylight - I assume that they use a whopping amount of power - but I don't know for sure.

Easy Peasy, I understand your concern. But I'd prefer the solution to not be that we encase our children in heavy SUVs, which threaten everyone. We've been using the trailer with our two kids for almost two years now and have never had a close call when towing it. Trailers and tagalongs are common in our neighborhood and are given wide berth by drivers who approach from the rear. My current concern is about side visibility when crossing intersections at twilight. And, as I noted upthread, I'm in the city (i.e., a traffic light or stop sign on *every corner*) and traffic is far more controlled than in the burbs. (All the close calls mentioned in this thread relate to my commute to work, after I've dropped the kids at preschool and ditched the trailer.)

Re bright clothes, I alternate between a bright (but not screaming) neon green and hot pink shirts. I think I really need to add a vest to get in the screaming neon tarwheel suggests. I don't see other cyclists round here wearing them but this has been a bad week (perhaps for the reasons Giro mentions).

I should have also specified in my original post that about 35% of my close calls lately are pedestrians who are watching just the car traffic and then step directly in front of me mid-block or cross against my green. There are not people busy texting, just people who apparently don't see me. Or misjudge my speed. If the latter, I'm not sure what to do about this.