UKH

I’m planning to start cycling to work soon, my journey home in the evening will be on an unlit A road, after 8pm (dusky - fully dark) or after 10pm ( definitely dark). 

What level of lighting can I get away with ( bearing in mind my budget is very limited)? The road takes in some steep hills so will pick up some speed at times. Is 400 lumens enough or should I be looking at 600 lumens as a minimum?

I used to have a light that was well sub 100 lumens but on dark night i would barely see people before i passed them. After a few near misses, i bought a light that gives 700 lumens on main beam.  It's far better, in fact it's too bright for street lit roads, or where pedestrians walk. The 300 lumen 'dipped beam' beam' is absolutely fine for those situations. But if you were bombing down an unlit road, i'd want at least 500.  And the dipped beam function is a must, otherwise you'll blind everyone else.

I have a Blackburn central 300 (supposedly 300 lumen) and find this is plenty to both see by on an unlit cycle path and be seen on a town road.

I also have a Chinese cheapo 1800 supposed lumen light which was good for racing through the woods on the MTB but totally overkill for road use and broke after about a year.

Yes 300-400 lumens is perfectly sufficient for unlit roads. 

How limited are we talking? I use this for going at speed on my roadie on country lanes:

http://www.magicshineuk.co.uk/bike-lights/front-bike-lights/mj-858-1000-lum...

1000 lumens for £60. I just have to make sure I dim it when I meet an oncoming car. 

To me more important than the light difference between 400 and 600 (it will be small - your perception of brightness is not linear) is the run time and the ease of re-charging.

https://www.sigmasports.com/item/Lezyne/Micro-500-Front-Light/GAN3

I have the 400 version

Has a few settings on it and one is the pulse mode, really good for not blinding drivers with flashing at night (which is actually illegal !!!)

The blinding bit or the flashing bit? I thought the law was changed a few years ago to accommodate the latter

Exposure Sirius for me - actually two, a mark 5 and a Mark 6 at 500 and 550 respectively.  the latter is on sale here.  I tend to have one flashing and one solid (two solid lights runs the risk of looking like a car a long way away, as opposed to a nearby bike).  

Flashing in town, solid beam when the street lights end.

On sale here:

https://www.tredz.co.uk/.Exposure-Sirius-Mk6-USB-Rechargeable-Front-Light-W...

Not had much luck with the batteries in Lezyne lights, so I've given up on them.

I originally had the Lezyne 400 and now have the Sirius Mk6 (which I only tend to run on half power).

Advantages of the Sirius (for me):  a sensible high/ low beam set up (i.e. yes, the lezyne has one but it is all or nothing); clean beam with good focus , not the widest but enough for road imo; quick release and sensible pocket size; no rear cap to get loose or lose; (manufacturer) replaceable battery.

My light has a mode where you can toggle between 150 lumen 'dipped' and 600 lumen 'full beam'. I like this as the 150 lumen is fine for street-lit areas and for riding on the flat / uphill. I only switch to full beam when bombing downhill, and to be honest any less than my full beam at 40mph would seem a little sketchy.

The spread of the beam will also affect how far ahead you can see too, so this is also worth looking at. One thing I've noticed is that oncoming traffic appreciates it when I dip my full beam for them (it is pretty bright)

Was thinking around the £30 mark. Guess I might just have to use the brakes more on the downhill stretches!

The only right answer is that you need ALL the lumens. Leave no one in any doubt that Apollo, the Sun God is on his way home as you pass them.

I'm afraid that at that price point you'll only really get lights to be seen rather than lights to see by.  It will be fine where there are street lights, but out where the buses don't run, it will just show you the object that you're about to hit. 

Of course, all of this is relative, and it will be far brighter than any incandescent bulb light that we coped with for years - more caution on the downhill and poor roads and you'll be fine.  If it's a regular trip, you'll soon learn where the big holes are.

Wiggle are doing the Lezyne Lite Drive 700 for £34.10. Should be bright enough for unlit descents and have less bright options for lit streets. Rear lights can be had for a couple of quid, I always think it is worth having a couple.

I have a knog arc blinder which I think is 640 lumens.  It has dimmer settings which I use if I am on longer rides in the dark as the brightest setting gives less than 90mins of light.  This would give you the option of brighter when you feel you need it or dimmer for most use.  I think they cost about £75.  My only complaint is that its poor offroad as the way it fastens doesn't cope with a bumpy ride and it doesn't give much warning when its running low.

yeh think you are right

https://www.bikeradar.com/road/gear/article/bike-light-laws-in-the-uk-what-...

I have one of the supposedly 1200 lumen Cree lights available from a well known on line seller, which gives more than enough light

There are well publicised instances of the battery packs catching fire when being recharged, I've had no problems with mine but don't leave it unattended and don't use it that regularly.

The other thing that you can do is have a look at the Road.cc 'beam comparison engine' which works really well

http://road.cc/content/buyers-guide/212914-best-20172018-front-lights-cycli...

I use a NiteRider MiNewt 600 - hase modes of 600, 400, 275 or 40 lumens. I mostly use the 400 setting.

Really good light, crap bracket!

There's also a 350 lumens version - available new on eBay for £45 posted.

Now replaced by the Lumina series, range of outputs, which has the same mount and a better bracket. I've upgraded to this bracket.

I use an exposure strada and joystick but that's over your budget.

You won't regret buying a good light, but you will regret buying a bad one, and it'll work out more expensive in the long run. 

Before the Exposure combo I used to run two lights on my bars, an Cateye Volt 300 and a B&M Ixon Core (they got nicked). The latter is a particularly good road riding light, not too expensive either, puts the light where you need it so doesn't dazzle cars, no flashing/pulsing mode. The pulsing mode on the Cateye volt is excellent too, flashing is difficult to gauge, pulsing is much easier

Interesting that it says "At night your cycle MUST have white front and red rear lights lit. It MUST also be fitted with a red rear reflector (and amber pedal reflectors, if manufactured after 1/10/85)."

How does the "amber pedal reflectors" bit cope with SPDs, not to mention the fact that most bikes come without pedals?

It also suggests not mounting your light on your helmet as you'll blind oncoming drivers. I find the opposite to be the case, giving you much more flexibility compared to bar mounting when it comes to pointing the beam away from oncoming traffic (and at it when it comes at you full beam).

A bike will have a reflector - it'll probably be in the little bag of instructions etc and no-one ever bothered to fit it, because everyone always takes them off anyway because they are just a few pennies of compliant plastic rubbish

The key word there is 'manufactured'.  If you buy a bike with pedals already fitted, it will come with amber reflectors.  Most road bikes don't come with pedals and so get around this silly bit of legislation as they don't have the pedals to which these reflectors must be fitted.  If a road bike does come with pedals, they will generally be the cheapest of cheap flats, with reflectors.