New CCTV cameras can track pedestrians around cities

The system assigns colours and numbers to pedestrians in order to track them across different cameras. Image: University of Washington.

After two pressure cooker bombs exploded during the Boston Marathon in April 2013, killing three and injuring around 300 more, it took police five days to track down the culprits. While thousands of officers scoured a 20-block area, transport systems were shut down and residents told to stay indoors.  

Now, just over a year later, an electrical engineer from the University of Washington says he has developed technology that would have shortened that manhunt to “hours, if not minutes”. 

That engineer is Jenq-Neng Hwang, who has created a system of cameras which use algorithms to track moving objects across large areas – even when they move out of sight of one camera and into the frame of another.

Before the cameras begin tracking, they record “training footage”, to understand how objects change in angles, texture and colour when viewed from the cameras’ respective locations. Once tracking, they assign moving objects colours and numbers, and use the information from the training footage to detect people already identified by another camera.

At the moment, the cameras can’t do this in real time - the technology operates as a faster version of officers searching footage frame-by-frame for suspects. But eventually, Hwang hopes these cameras could operate around cities, on drones and in robots to track suspects or create a kind of moving Google Earth, with maps populated by cars and people. You could, for example, see the traffic on a road you’re about to travel to, or use a tracking drone to find survivors after a natural disaster.   

In the video below, Hwang admits there are “privacy issues” surrounding this vision. But to him, it seems absurd that we collect millions of hours of CCTV footage in cities, only for it to “end up on servers, never to be viewed again”.

One idea that does seem a little excessive is the use of the cameras in shops, to collect what Hwang calls “valuable information about a specific shopper’s preferences”.  While he enticingly says this information would be used to send shoppers “special coupons”, we’d probably rather shop without a robot salesman breathing down our necks.

All images: University of Washington. 

 
 
 
 

Tackling toxic air in our cities is also a matter of social justice

Oh, lovely. Image: Getty.

Clean Air Zones are often dismissed by critics as socially unfair. The thinking goes that charging older and more polluting private cars will disproportionately impact lower income households who cannot afford expensive cleaner alternatives such as electric vehicles.

But this argument doesn’t consider who is most affected by polluted air. When comparing the latest deprivation data to nitrogen dioxide background concentration data, the relationship is clear: the most polluted areas are also disproportionately poorer.

In UK cities, 16 per cent of people living in the most polluted areas also live in one of the top 10 per cent most deprived neighbourhoods, against 2 per cent who live in the least deprived areas.

The graph below shows the average background concentration of NO2 compared against neighbourhoods ranked by deprivation. For all English cities in aggregate, pollution levels rise as neighbourhoods become more deprived (although interestingly this pattern doesn’t hold for more rural areas).

Average NO2 concentration and deprivation levels. Source: IMD, MHCLG (2019); background mapping for local authorities, Defra (2019).

The graph also shows the cities in which the gap in pollution concentration between the most and the least deprived areas is the highest, which includes some of the UK’s largest urban areas.  In Sheffield, Leeds and Birmingham, there is a respective 46, 42 and 33 per cent difference in NO2 concentration between the poorest and the wealthiest areas – almost double the national urban average gap, at around 26 per cent.

One possible explanation for these inequalities in exposure to toxic air is that low-income people are more likely to live near busy roads. Our data on roadside pollution suggests that, in London, 50 per cent of roads located in the most deprived areas are above legal limits, against 4 per cent in the least deprived. In a number of large cities (Birmingham, Manchester, Sheffield), none of the roads located in the least deprived areas are estimated to be breaching legal limits.

This has a knock-on impact on health. Poor quality air is known to cause health issues such as cardiovascular disease, lung cancer and asthma. Given the particularly poor quality of air in deprived areas, this is likely to contribute to the gap in health and life expectancy inequalities as well as economic ones between neighbourhoods.


The financial impact of policies such as clean air zones on poorer people is a valid concern. But it is not a justifiable reason for inaction. Mitigating policies such as scrappage schemes, which have been put in place in London, can deal with the former concern while still targeting an issue that disproportionately affects the poor.

As the Centre for Cities’ Cities Outlook report showed, people are dying across the country as a result of the air that they breathe. Clean air zones are one of a number of policies that cities can use to help reduce this, with benefits for their poorer residents in particular.

Valentine Quinio is a researcher at the Centre for Cities, on whose blog this post first appeared.