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.

 
 
 
 

“Ministers are ignoring the people who’ll deal with the fallout from Brexit”: The case for a second referendum

Everything is fine: Prime minister Theresa May and Liverpool mayor Joe Anderson. Image: Getty.

We’ve come a long way from the days when Brexiteers promised a free trade utopia and an £350m a week to spend on our NHS. Now we have David Davis reduced to warning there will be no Mad Max-style scenario when we leave the European Union.

Anyway, how do we know? The Brexit Secretary refuses to publish his economic risk analysis so we can have an informed discussion about the effects on cities like mine. What evidence has trickled out of his department shows that the UK economy will take a hit – and the further you are away from Greater London, the harder that punch will feel.

At best, with retained access to the single market, we will take a 2 per cent hit to GDP over the next 15 years. At worst, with a so-called ‘Hard Brexit’, this increases to 8 per cent.

That’s hundreds of thousands of jobs taken out of the economy. Moreover, we know the impact will be felt unevenly. The further away you are from London and the South East, the deeper the effects.

This week, leaders of some of our major Core Cities met Michel Barnier, the EU’s chief negotiator, to explain our worries. Our cities are potential engines of growth and vital players as we insulate the country from Brexit-related shocks. We are trying to play a constructive role – whether or not we agree with Brexit – because we are on the ground and left dealing with the fallout.

So far, ministers have refused to meet us. We are apparently frozen out of the conversation because our reality-based concerns do not fit with the government’s celestial belief that things will be all right on the night.

As a local government leader, I deal in pragmatic solutions. (Having lost two-thirds of our Government funding since 2010, I have no choice.) But ministers need to come out of their bunker and talk to us about the support we need and the part we can play in preventing a recession when we leave the EU.


There is only one way to interpret their reluctance to do so. They know that we are on course to take an economic shellacking, and are preparing to leave us to it. They have done nothing to reassure us that a dystopian nightmare does not await – with Britain reduced a low-tax, low regulation fiefdom, with neo-liberal hardliners taking a red pen to the social and environmental protections currently guaranteed by EU law.

This is not acceptable. It is a total betrayal of those parts of the country already struggling with a decade of austerity and all the uncertainty generated by the Brexit process. But ministers should care because if we suffer, then Brexit will have demonstrably failed.

It will come as little surprise to Scousers. Liverpool voted 58 per cent to Remain back in June 2016. That’s because we felt the practical benefits of being in the EU. Europe was there for us – especially in the 1980s – when our own government wasn’t.

Objective One and other regional funding streams helped bring Liverpool back from the dark days when ministers in the Thatcher Government were seriously contemplating writing us off entirely. ‘Managed decline’ they called it. We were to be left to fend for ourselves.

But Europe allowed us to begin a ‘managed renaissance,’ becoming the modern, optimistic and dynamic city we are today. EU funding helped us to bounce back and catalysed many of the dramatic changes we’ve seen over the past few years.

If leaving the EU now results in a harsh economic winter, then the pendulum of public opinion will swing back the other way. So it’s actually in the interests of Brexiteers to have a second vote on the terms of our departure.  Asking the public if they approve of the deal ministers will have negotiated, is entirely justified. Call it a confirmatory ballot, or a cooling-off vote.

This is not about keeping asking the same question until the political elite get the answer they want. It is about giving the British people sign-off on how the country will be governed after 2019 and the effects that will have on their lives.

It’s ridiculous that we have more opportunity when it comes to cancelling our car insurance than have when it comes to reflecting on the biggest change to Britain’s economic and political fortunes in any of our lifetimes.

If – after knowing the full facts of what we face on the outside – the British public still voted to leave, then I would accept their decision with no further protest – and so should everyone else.

But it is right to ask them.

What is not acceptable – or credible – is to ignore reality and refuse to deal with the very people who will be left to pick up the pieces.

Joe Anderson is the Labour mayor of Liverpool.