This is why pedestrians and cyclists disappear when it starts getting dark

Where did everybody go? Darkened London streets, 1929 vintage. Image: Getty.

Picture the scene: it is 5:30pm on a Tuesday at the end of October, and the streets are full of people walking and cycling home from work. The following week, at the same time, the number of walkers and cyclists has dropped by almost half. The only difference is the clocks have moved back one hour to mark the beginning of Daylight Saving Time.

Naturally, the number of people walking or cycling varies greatly at different times during the day. But twice every year, when the clocks change, researchers like myself get a rare opportunity to compare numbers of pedestrians and cyclists in the same hour of the day, but under different lighting conditions. This enables us to measure the impact that darkness has on how people choose to get around, while other influential factors such as the reason for travelling or the temperature remain largely unchanged.

Using open-source data from automated pedestrian and cyclist counters in a United States district, my colleagues and I analysed the number of pedestrians and cyclists in the same hour of the day, over a two-week period, both before and after the clocks changed.

Darkness effectively reduced the volume of pedestrians by 38 per cent and the volume of cyclists by 27 per cent, after taking into account any changes unrelated to light conditions.

Night and day

There are a number of reasons why people might prefer not to walk or cycle after dark. It’s more difficult to see the path when it’s dark and harder to spot potential trip hazards. Pedestrians have to spend more time looking down and are also less likely to be able to detect obstacles.

Darkness also makes it more difficult for walkers and cyclists to be seen by other road users. As a result, pedestrians are 1.7 times more likely to be hit by a vehicle while using a pedestrian crossing at night, compared with during the day.

Example pedestrian crossing in daylight (left) and after-dark (right). Image: author provided.

Another reason people may not choose to walk or cycle when it is dark is because they feel less safe. One theory suggests that people assess the safety of an environment based on three things: the ability to see clearly for a distance, the presence of features which could conceal a threat and the potential to escape from the area. Therefore, most places are likely to feel less safe at night, because we cannot see as well in the dark.

Fighting the darkness

Ideally, people should be encouraged to walk or cycle, even when it turns dark, because of the huge potential health and environmental benefits. Of course, networks of public street lights have been combating darkness in cities since the 19th century, following the discovery of coal-gas as an illuminant by Scottish engineer William Murdoch. Smoking his pipe beside a fire one night, Murdoch decided to put coal dust in the pipe and put it in the fire. The bright flame that emerged from the mouthpiece prompted the revelation of using gas as a light source.

William Murdoch, pioneer of street gas-lighting. Image: Wikimedia Commons.

But it’s increasingly important to use street lighting effectively to avoid wasting energy and creating needless light pollution, which can have negative effects on plants and animals. To that end, lots of research has been carried out to pinpoint the perfect level of lighting, which still enables pedestrians and cyclists to see effectively without wasting any energy.

Current guidelines for street lighting recommend average light levels of two to 15 lux, depending on the type of street. The evidence supporting these guidelines may be flawed however. The 2.5 GWh of energy used by street lighting every year may therefore be misplaced.

Laboratory research has been conducted to measure the impact of light spectrum and intensity on a pedestrian’s ability to detect a trip hazard. The study found that people are able to perceive a hazard with just two lux of illuminance. When the light was brighter than this, people did not get any better at detecting hazards.

The research also found that white light can be used at lower intensities, without affecting pedestrians’ visual performance. Similar results were found for cyclists’ ability to detect hazards.

Experimental apparatus to assess effect of lighting on cyclists’ detection of a hazard in the road (Fotios, Qasem, Cheal & Uttley, 2017).

Building on work carried out in the US at the end of the 1990s, our team at Sheffield University is also trying to identify lighting conditions which help people feel safe on the streets at night. The US research, carried out in parking lots, found that people felt safer when lights were brighter but that the benefits did not increase correspondingly as brightness increased. We are now verifying these findings on residential streets.

The change of the clocks every autumn – and the earlier onset of darkness – serves as a reminder of how significant daylight is to people’s everyday behaviour, particularly the way they choose to travel. Lighting can help us continue our day-to-day lives even when the sun goes down – and in this new age of highly controllable and efficient LED lighting it is tempting to assume “the more light the better”.


The ConversationIdentifying lighting conditions that meet our requirements without being excessive can help us save energy, reduce carbon emissions, reduce the ecological impact of our lighting and even make astronomers happier.

Jim Uttley is a postdoctoral researcher in lighting & environmental psychology at the University of Sheffield.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

What is to be done? Some modest suggestions on solving the NIMBY problem

Lovely, lovely houses. Image: Getty.

The thing about NIMBYism, right, is that there’s no downside to it. If you already own a decent size house, then the fact a city isn’t building enough homes to go round is probably no skin off your nose. Quite the opposite, in fact: you’ll actively benefit from higher house prices.

So it’s little wonder that campaigning against property development is a popular leisure activity among those looking forward to a long retirement (don’t Google it, it’ll only depress you). It’s sociable, it’s profitable, it only takes a few hours a week, and, best of all, it makes you feel righteous, like you’re doing something good. In those circumstances, who wouldn’t be a NIMBY?

To fight the scourge of NIMBYism, then, what we need to do is to rebalance the risks and rewards that its participants face. By increasing the costs of opposing new housebuilding, we can make sure that people only do it when said development is genuinely a horror worth fighting – rather than, say, something less than perfect that pops up a Tuesday afternoon when they don’t have much else on.

Here are some reasonable and sensible ideas for policies to make that happen.

A NIMBY licence, priced at, say, £150 a month. Anyone found practicing NIMBYism without a licence faces a fine of £5,000. Excellent revenue raiser for the Treasury.

Prison sentences for NIMBYs. Not all of them, obviously – we’re not barbarians – but if the planning process concludes that a development will be good for the community, then those who tried to prevent it should be seen as anti-social elements and treated accordingly.

A NIMBY lottery. All homeowners wishing to oppose a new development must enter their details into an official government lottery scheme. If their number comes up, then their house gets CPOed and redeveloped as flats. Turns NIMBYism into a form of Russian roulette, but with compulsory purchase orders instead of bullets.

This one is actually a huge range of different policies depending on what you make the odds. At one end of the scale, losing your house is pretty unlikely: you’d think twice, but you’re probably fine. At the other, basically everyone who opposes a scheme will lose their entire worldly wealth the moment it gets planning approval, so you’d have to be very, very sure it was bad before you even thought about sticking your head above the parapet. So the question is: do you feel lucky?


NIMBY shaming. There are tribal cultures where, when a member does something terrible, they never see them again. Never talk to them, never look at them, never acknowledge them in any way. To the tribe, this person is dead.

I’m just saying, it’s an option.

A NIMBY-specific bedroom tax. Oppose new housing development to your heart’s content, but be prepared to pay for any space you don’t need. I can’t think of any jokes here, now I’ve written it down I think this one’s genuinely quite sensible.

Capital punishment for NIMBYs. This one’s a bit on the extreme side, so to keep things reasonable it would only apply to those NIMBYs who believe in capital punishment for other sorts of crime. Fair’s far.

Pushing snails through their letter boxes. This probably won’t stop them, but it’d make me feel better. The snails, not so much.

Reformed property taxes, which tax increases in house prices, so discourage homeowners from treating them as effectively free money.

Sorry, I’m just being silly now, aren’t I?

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason.

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