# How long before sunrise can one ride with adequate visibility?



## Gordon Gekko (Jan 24, 2008)

What is the earliest you would consider riding in the morning relative to sunlight? According to weather.com, the sun rises at 6:44 am in SoCal. But, I see riders already on the road before 6:44 am so I suspect there is adequate visibility well before sunrise. How early do you guys ride?


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## Pablo (Jul 7, 2004)

I commute year round, including part of the year where my entire hour-long commute is in the dark before the sun's up. From my experience, there's some fairly adequate visibility for you, the cyclist, about 20 minutes or so before the sun actually peaks (or is it "peeks") over the horizon. 

The issue, however, is not so much whether you can see during this period, but rather, is whether cars can see you. If you ride during this period, I'd suggest strongly getting a little flashing tail light for you and/or your bike.


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## Sprocket - Matt (Sep 13, 2005)

Depends on your town too....

http://news.bbc.co.uk/2/hi/europe/6189371.stm


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## Allez Rouge (Jan 1, 1970)

There is a period known as "civil twilight" which is, technically, when the sun is within 6deg of the horizon (whether rising or having already set), and during which it is considered light enough to conduct activities outdoors without artificial lighting. Check Wikipedia for a full explanation.

Then go here to compute when civil twilight begins and ends for your location on any given day. Although the length of time between CT's limits and sunrise/sunset will vary depending on the time of year, you'll see that it roughly conforms to the 20 minute period that Pablo mentions.

And he's right on about seeing vs being seen. Although you will be able to see adequately during civil twilight, you'll be virtually invisible to motorists until they're right on top of you.


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## AlexCad5 (Jan 2, 2005)

Lights work really well.


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## Pablo (Jul 7, 2004)

Allez Rouge said:


> And he's right on about seeing vs being seen. Although you will be able to see adequately during civil twilight, you'll be virtually invisible to motorists until they're right on top of you.


I only really noticed it when I occasionally drive. From a car, it's really hard to see anything during this window of time. 

I'm actually more nervous during this period than when it's fully dark out becasue, due to the sunlight still in the air, my tail lights are also relatively hard to see. It's best to avoid any busy streets, if possible, during this time.


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## slitespd (Nov 2, 2004)

All night long if you want to!


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## Dave Hickey (Jan 27, 2002)

Pablo said:


> The issue, however, is not so much whether you can see during this period, but rather, is whether cars can see you. If you ride during this period, I'd suggest strongly getting a little flashing tail light for you and/or your bike.


Just to add to Pablos comments. Also be very careful riding when the sun is low on the horizon. Drivers have a very hard time seeing you when they are driving in the direction of the sun...


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## Mr Wood (Feb 23, 2006)

Another site to check out the sunrise and sunset times. If you click on "custom sunrise and sunset calendar", you can print a calendar with civil twilight, nautical twilight and astronomical twilight. It also has definitions of each term.

http://www.sunrisesunset.com

Civil Twilight
Civil twilight is defined when the sun is 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.

Nautical Twilight
Nautical twilight is defined when the sun is 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.

Astronomical Twilight
Astronomical twilight is defined when the sun is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening the sun does not contribute to sky illumination; for a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible.


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## lot8con8 (May 17, 2006)

Another factor is the weather; cloudy days vs. sunny days. Overcast skies will affect the amount of visibility in the early morning hours. Add in fog or other weathe factors as well. Watch your weather forecast.


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## Creakyknees (Sep 21, 2003)

Just get good night gear - lights, reflective stuff, neon jacket, and run it. When the sun rises, turn off your lights.


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## California L33 (Jan 20, 2006)

I agree with Creakyknees. There's a lot of lighting info over on RBR's sister site, MTBR. There should be a link at the bottom of this page.


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## TheDon (Feb 3, 2006)

I would avoid riding in civil twilight. Lights aren't going to be too useful unless your lights are really bright and flashy.


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## thegock (May 16, 2006)

*Commuting sporadically for the past two years...*

+1 on the twenty minutes.

I use two blinkies-one on seat and one on helmet (in case one fails and to make a better case in the civil court where my estate might be the plantiff) and an HID for the commute.


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## tarwheel2 (Jul 7, 2005)

Get a good headlight and tail-light(s). No point guessing about whether visibility is good enough. With a decent headlight, you'll actually see better when it's dark than in twilight. It's dark when I leave for work about 6:30 am, and it's light enough to see without my headlight about halfway through the ride, but I keep my light burning the whole way for visibility. Coming home, it's light enough to see without my headlight the entire way, but I still burn my headlight. I run tail-lights all the time on my commutes until the days get long enough where it's bright outside the whole way -- that is, no twilight.

My main point is that during twilight or dark conditions, you need to lights to be seen as well as to see.


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## 99trek5200 (Jan 26, 2007)

It's more about others visabiltiy of you, not you of them. This is something that irks me about drivers.

I see so many drivers with no lights on when it is foggy or dusk cause they can see the road. What they don't seem to realize is that others can't see their silver car until they are right on top of them. What I totally don't get are those that recognize that it is dusk so they turn on their parking lights. It's like they made the effort, but just couldn't commit to turning on their lights. Parking lights are just that, lights so that you can be seen when you are parked. (i.e. not moving)

I am now off my soap box and return you to your regularly scheduled thread.

Get lights. Blinking rear light and a helmet and bar light for the front. A blinking front light draws more attention during dusk/daylight hours.


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## tarwheel2 (Jul 7, 2005)

*lights*



99trek5200 said:


> This is something that irks me about drivers. I see so many drivers with no lights on when it is foggy or dusk cause they can see the road.


Some drivers apparently must think it saves gas to not burn their headlights. Either that or they are just clueless. I saw a car yesterday with no headlights or parking lights on at 6:30 am and it was almost totally dark. I don't know how he could even see where to drive.


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## Pablo (Jul 7, 2004)

tarwheel2 said:


> Some drivers apparently must think it saves gas to not burn their headlights. Either that or they are just clueless. I saw a car yesterday with no headlights or parking lights on at 6:30 am and it was almost totally dark. I don't know how he could even see where to drive.


It's dumb, but people often don't turn their lights on in the mornings so that they don't accidentally leave them on and kill the battery.


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## AlexCad5 (Jan 2, 2005)

99trek5200 said:


> It's more about others visabiltiy of you, not you of them.


 A good light will give you a chance to avoid that dead dear or tree limb in the middle of the road before it's too late. Sometimes you can find yourself on a road with no moonlight and no streetlights and no cars and you can barely make out the white line on the side of the road. Pitch black is dangerous on a bike.


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## solorider (Aug 16, 2004)

Not to highjack the post, but why isn't there a good discussion of roadie friendly lights. It seems like the MTB guys like to have 1 Million Candle Power Laser Beams.

I on the other hand would like a light that covers me for the 45 minutes before sun up.

I've got young kids and if I'm going to ride on the weekends in a wife friendly manner I've got to be up and back before the kids are ready for breakfast.

I've been looking at the Light and Motion Vega 4 Watt LED for $179 or the Catevey HL-EL530 for $59.95. Their not lasers so they don't get reviewed.


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## Slim Again Soon (Oct 25, 2005)

*Cool site -- thanks*

"Then go here to compute when civil twilight begins...."


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## California L33 (Jan 20, 2006)

solorider said:


> Not to highjack the post, but why isn't there a good discussion of roadie friendly lights. It seems like the MTB guys like to have 1 Million Candle Power Laser Beams.
> 
> I on the other hand would like a light that covers me for the 45 minutes before sun up.
> 
> ...


It really depends on how fast you go, and whether you've want a light to see or be seen. I think the Cateye is going to be a 'be seen' light. A 4 watt LED will give you some usable light, but even with 10 watts of LED I find anything much over 20MPH a bit risky. I've told the story a few times, but when I first got my 30 watt halogen system (a little less usable light than the 10 watt LED system) I thought I could descend with impunity- I'd be able to see anything big enough to cause problems with the spill, and anything small would be in their beams and easy enough to steer around, and besides, I was riding familiar roads and knew where all the potholes were. I was doing about 35MPH when something I hadn't thought of popped into the beam. A piece of metal flashing about the dimensions of a 2x4 and 5 feet long appeared directly across my path- no way to stop and no way to steer around it. I tried to jump but still caught a bit of it with my front tire, then it bounced into my BB, then my rear tire. I got lucky- stayed upright, no real damage to me or the bike, but it did get the adrenaline pumping. 

Naturally you'll want a taillight, too. The big 10 LED Cateye is good, the Dinotte is in a class by itself, but pricey.

And as others have said, that period right after the sun rises is a bit risky when drivers are looking into the sun. Remember, if you've got a great view of the cars chances are they're almost blind and no light will help.


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## Becky (Jun 15, 2004)

Ditto on the 10-LED Cateye tail light. DH and I each have one on our commuters and, in flash mode, you can't help but see them. For a front light, we're running first-gen MiNewts, and they've been more than adequate for lit city streets at civil twilight or thereabouts. If I could have gotten a MiNewt.X2 at the time, I would have. The L&M Vega is supposed to be a sweet little light, and would be a good choice if you need to remove your lights when you leave the bike since the battery is self-contained.


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