Why Am I Biking in the Dark?

Daylight Savings ends on Sunday, and with it the light in the evening. Daylight savings, as many of you know, exists as part of an energy savings program and was last expanded as part of the 2005 Energy Bill. There is some debate as to whether it has led to less electricity use or not. A 2008 study by the Department of Energy said it decreased energy use by 0.03%, but others say it increases energy use by 1% or more. [I don't understand how, in the name of good energy policy, we can literally change time, but we can't get a carbon tax, but that's another issue].

So what does this change do to bike commuting. Next week, most bike commuters will ride home in the dark. And many will bike to work in the dark too. Winter is a more dangerous time to bike commute for this reason. Does daylight savings make it more dangerous? Does it dissuade bike commuters?

One study - based on data from Arlington's bike counters (hooray local government) - showed that changes in light resulted in changes in bike and walk commuting. And that the number of people actively commuting changed significantly near the clock change, with people doing less of it when it is dark. This change was lower for cyclists than pedestrians.

Odds ratios indicated the numbers of pedestrians and cyclists during the case period were significantly higher during daylight conditions than after-dark, resulting in a 62% increase in pedestrians and a 38% increase in cyclists.  

There are large peaks in cyclist frequencies at morning and evening commuter times, and whether the case hour is in daylight or darkness does not alter the timing of these peaks. This supports the suggestion that cyclists may be quite rigid in their travel times, producing a relatively limited spillover effect. 

They also believe that lighting plays a part in this because trail commuting goes down more than on-road commuting.

the transition between darkness and daylight during the case period had a greater effect on cyclist frequencies at trail locations, compared with cycle lane locations.

Meaning that one conclusion is that we need more lighting on bike commuter routes (recognizing that it should be environmentally appropriate) if we want more people to bike commute in the winter. 

Another conclusion the studies show is that it is darkness, more than the cold, that causes bike commuting to drop in the winter (which echoes my opinion that it's the dark that I find more unpleasant than the temperature). When non-cyclists argue that people won't bike all year, they talk about the cold, but this indicates that they're wrong, and may explain why biking commuting doesn't 1) go down when it gets really hot 2) go down more in colder climate cities than warmer ones.

The transition in ambient light condition alone can explain the increase in pedestrians and cyclists during the daylight periods independently from any influence of temperature. In fact, the clock changes that showed no change in temperature generally produced larger odds ratios than those clock changes where the temperature did change significantly. This would suggest the effect of the transition in light conditions was larger when there was no temperature change.

This means that the more that we can move the rush hours into daylight, the more we'll encourage active transportation. Next week, we'll lose light in the evening rush in exchange for an hour in the morning rush, but I feel like it's not a good trade. We give up 5-6pm for 6:30-7:30am and you can see from that bicycle counter data that this is a bad trade. We give up our 2nd (and nearly top) biking hour in the evening in exchange for a mid-level hour in the morning. We're also giving up a time that many kids are being picked up from daycare and aftercare and also more likely to be out and about, for a time when many are still asleep or at home. Like I said, I think it's a bad trade. 

So daylight savings has some impact on how many people commute, but what about safety? Unsurprisingly, this has been studied in the US and unsurprisingly, having light at the time when more people commute is expected to save lives.

Results show that full year daylight saving time would reduce pedestrian fatalities by 171 per year, or by 13% of all pedestrian fatalities in the 5:00–10.00 a.m. and in the 4:00–9:00 p.m. time periods. Motor vehicle occupant fatalities would be reduced by 195 per year, or 3%, during the same time periods.

Same in the UK

operating daylight saving year-round would have a small but tangible effect on the number of serious and fatal road traffic injuries in children in this area.

And of just pedestrians

there was a significantly greater risk of a pedestrian [road traffic collisions] at a crossing after-dark than during daylight.

Other studies indicate that this isn't due to changes in Circadian rhythm. The shift in sleep leads to an increase in accidents in the spring and a decrease in the fall.

The spring shift to daylight savings time, and the concomitant loss of one hour of sleep, resulted in an average increase in traffic accidents of approximately 8 percent, whereas the fall shift resulted in a decrease in accidents of approximately the same magnitude immediately after the time shift.

Though it's not a local issue, we should consider extending daylight savings year round. There's a question about what that does to energy consumption and that might require a trade off; but it does seem it would make the roads safer and encourage more bike commuting and walk commuting (which could offset any energy impacts).

Even if we don't change daylight savings, we need to install brighter and better lighting on bike routes, pedestrian commuter routes and at crosswalks.

Comments

[huskerdont]

Trail lighting. Even along the Custis, which has some lights, the debris in the dark can be a problem, though I use a 600 lumin headlamp and weaker handlebar lamp. I feel the lights there are placed more to deter crime than for seeing where you're going. The other morning I used some of the W&OD and noticed there were no lights at all on that portion. Last night coming back from DC United after 11:00, the MVT was pretty rough in the dark with the root heaves and overgrown edges (and going in against the car headlights was something I had not experienced before and would prefer not to again). Traffic engineers do all these things for motorist safety, but there's not a similar focus for trails, even in a place like Arlington; I suppose I wouldn't expect more for the mode share, but if they're interested in building it...

I'm early enough that I've been in the dark in the morning for more than a month now; with the change, I'll briefly see some sunrises again. The positive side is the afternoon commute, which I feel is more dangerous because there's more traffic, is never completely dark for me. Unless we shorten work days, there's no way not to commute in the dark. I'd love to shorten the work days.

[Purple Eagle]

I have noticed the root bumps and other pavement irregularities are getting really bad on the MVT between Roosevelt Island and 14th St. And no lighting on this section.

[Crickey]

I was following behind someone the other night on the CCT who had weak lights. He juked to avoid something on the trail, I didn't have time to react, and I was down before you can say "Class 1 E-bike".

[Jack’srup]

A big problem on the trails at night is bikers, joggers, and walkers without lights or even any reflective clothing. I can catch most of them with my headlight before it’s too late, but sometimes it’s a close call, especially with stealth bikers coming from the opposite direction. If you’re on the trails at night, GET SOME LIGHTS! Front and back. Same goes if you’re walking or running. And pls no front flashers while you’re on the trails—they are obnoxious and don’t help you see anything. Even better, get a front light with a European type light cutoff so you don’t blind all your fellow trail users.

[Michael]

What's the difference between "extending daylight savings year round" and never switching at all?

[Jeffb]

When I became a 3-season commuter the shift back to regular time was my signal to cease cycling for the year. The shock was too great.

If there was no time shift then losing a minute or 2 of daylight in the evening easy day might have been gradual enough to keep me cycling longer into the season.

Also, the earliest sunset occurs around Dec 6th so light for the evening commute starts improving well before the worst of Winter weather has set in.

[DE]

For the last 8 years I've seen this same ninja jogger on the Custis most mornings. She always wears all black and has a cap she pulls down over her eyes so that peoples' lights don't bother her. Thing is, without the bright light, I might not see her. (I do turn my headlight aside when it's safe to do so.) But I don't worry about it too much, and she was nice enough to check that I was okay when I wiped out on the ice once. People are going to do what they're going to do.

[mary stone]

If daylight savings time has ended, is it now daylight spending time? And how did 4 months out of 12 become 'standard' time?

[fongfong]

I'm indifferent to the change. Regardless, I will be biking in the am or pm in the dark, so for me it is an equivalent proposition.

Since I have a 9 year old kid, getting him to wake up with the dawn under standard time is helpful, so there's that.

Do I get to now be the grumpy guy complaining about folks with 800 lumen flashers I can see a mile away? My pet peeve. I will only crash into you once you get near me, so tone it down.

OTOH, I will not be one of those folks who first covers their headlight and then shouts at oncoming bikes on the paths "shield your light!" when they don't do likewise. This is passive/aggressive behavior and you can't make people follow your lead. The brightness of an oncoming headlight is no worse than car headlights on a two-lane road. Deal with it and stop being like that.

[washcycle]

What's the difference between "extending daylight savings year round" and never switching at all?

It's the same thing. But we'd be permanently shifted by an hour from other time zones.