Is there a real bike light with hi/lo-beam?

That 800 lumen spillbeam directed onto incoming traffic is really quite glaring. Is there an LED light that has proper cutoff like a car headlamp?

I know what you mean.

I am torn between needing to be seen by every driver at night, and not wanting to cause an accident by blinding said drivers.

Also, will you want to switch to high to warn an oncoming driver that you suspect hasn't seen you, or is likely to crash into you if he continues his current trajectory - That's what I would do in a car for instance. What will dazzle a car driver may be overlooked by a lorry or bus driver as their elevation is possibly out of the spill of your light.

Basically what I find works is a bright floody light pointed at the road - with only minimal spill going into oncoming traffic - this is to keep me safe from potholes (Loads of them where I come from, because of the lorries and buses as it happens. (I use a Klarus XT10 on medium for this - at 150 lumen)

Next to that I have a beacon style light - flashing or pulsing - this is aimed to be in the eyeline of oncoming traffic - but shouldn't dazzle - the briefness of the powerful flash merely secures direction and not blindness (lots of bike lights do this - I use a Jetbeam ST Cycler)

And finally for maximum visibility I have a light on my helmet - I use a Fenix HP 11 - which is a four level thrower with some spill - I use whatever level necessary to be seen and to light up problems ahead - When a car is about to come out of a side road in front of me (my right of way) I will look directly at the driver for a couple of 'flashes' - this normally gets them to stop and I can continue without incident. I find this more handy than reaching for a switch as you would have to do with a high beam control, as well as being able to keep it out of the eyes of oncoming traffic that isn't about to run you down. (generally use level 3 at night - 133 lumen in a tightish spot)

Taxi drivers seem very appreciative of this and I have received compliments on the efficacy of the headlamp (no, really - they like it)

I think 800 lumen is overkill for city or traffic driving, except for night off roading. Apart from anything else, you'll probably get loads of complaints from other cyclists too!

You should look into the bicycle subforum. The Philips Saferide LED bikelight might be what You are looking for. I use it and I'm very happy with it.

install Your "beam" as it is the one and only useful way:
pointing slightly down!

the upper end of the beam should be somewhere 30-50 meters in front of Your bike
(depending on Your speed, on the lights around, on Your imagination of "blinding" oncoming traffic, ...)

then noone gets the main beam and there is no problem at all


but stay serious:
any BIKE with a standard bike light (= non selfbuilt supersun model) that would "blind" me - when sitting in the car - gets a 110 Watt high beam flash. That will immediately inform the biker to please reduce the output, or point the beam more down, or whatever ... at least the effect of his/her light is neglectible then.
Whoever driver is "blinded" by an 800 Lumen led/halo portable light - even when it is mounted incorrectly - has to
1st: stop the damned car and
2nd: give back the license and go by food

You should also look at this forum - specially the light DIY. Lots of great ideas:
http://forums.mtbr.com/lights-diy-do-yourself/

Will