Migration can kill


Since my wander around St Loyes with Rosie King, I’ve been continuing to think about migration patterns. On the walk, we reflected on migration into the area to live, as developers built wave after wave of suburbia. We also thought about the annual migration of holiday-makers to the SW through J30 services, and the daily migration of workers on Sowton Industrial Estate. This last became particular obvious to me during “The Birds of Sowton Industrial Estate”, as it emptied of cars at the end of the working day.

Is it possible to get hold of data that show these migratory patterns of traffic flows? I could find some annual traffic counts for road junctions in Devon from the Department of Transport, but nothing weekly, daily or hourly that showed the seasonal or daily patterns.

What of proxies? Under the Working with Gold umbrella in 2018, I also had the idea of going on random picnics and measuring air quality. The picnics didn’t happen during the year of the programme, but there are air quality monitoring stations by roadsides in Exeter that I thought should have hourly data.

Defra has responsibility for the national air quality monitoring network, and it is possible to request data across the network. However, it includes only one site in Exeter. The Exeter DataMill is easier to use, and it contains monthly NO2 concentrations for numerous sites around the city and hourly particulate matter (PM10) at two high-traffic sites: Exeter Roadside (at RAMM) and Alphington Street (at the traffic lights before the railway bridge).

Ideally, I’d like to visualise waves of traffic flowing and ebbing through Exeter. Given that I had air pollution data, and its dire effects on our health and quality of life, I chose a health-related visualisation.

And so back to Processing, and struggling to embed it in a website. This time, though, I have discovered p5.js, a Javascript library that interprets Processing for the web. (It turns out that there is also a p5.EasyCam library that is a derivative of the original PeasyCam library, and means I might be able to get the meteorites on the web.)

Here then are PM10 concentrations (μg/m3) at Exeter Roadside and Alphington Street, for 1 Jan 2016 – 19 Jan 2017, averaged across the hour of the day and the day of the week. They clearly show the morning rush hour on weekdays, when the school run and commute coincide, and the lower longer evening rush hour. You can also see the morning flow to the shops and evening ebb during the weekend.

The question that remains with me is: How do we make this migration pattern less harmful? How can we persuade people out of their cars and onto their bikes/feet?