More data for better air in London

Leapcraft accentuates London’s air quality data with real time emissions data from mobile sensors

By: Priya Mani

07 May 2018

CPHSense-mounted buses in London on Route 25 and Route 58. The sensors were driven for 4 weeks between March 2017 and April 2017 generating thousands of data points on road traffic in London.

LONDON is very fortunate to have one of the most robust air quality monitoring networks in the world combined with the ingenious scientific knowledge to build tools and mathematical models to stay updated on that. But,that said, London is also dogged by one of the worst atmospheric air pollutions in the world. High intensity public transport that ferries a burgeoning population, traffic and congestion, construction and new developments all contribute to the cocktail in the air and a whimsical weather that doesn’t really help the situation.

To monitor this, London has been an early actor in establishing many air quality monitoring stations across the city. These networks are mainly expensive, high accuracy automatic air quality monitors, which are stationary, lab grade equipment and are distributed amongst the 33 boroughs of Greater London Area. The high costs and installation resources needed for these stations means that only so few have been deployed in Greater London Area with scientists having only one or two reference data points in each borough and leaving the rest of the pollution measurements and forecasting to sophisticated mathematical modelling.

Leapcraft leveraged an innovative deployment strategy with mobile sensors mounted on London’s city buses as an experiment to create a more complete and detailed observational baseline to complement London’s high accuracy automatic air quality monitors.

With a special deployment focus on high density public areas, schools, hospitals and heavily trafficked roads we can see the extent to which pollution hotspots, as identified by the local authorities, exist and change daily and seasonally.

The innovation Leapcraft brought was to couple existing open data along with general insights into pollution dynamics along with a critical dialogue with the authorities to deploy at a scale where key focus areas and their sources are targeted for generating useful information.

Keeping this in mind Leapcraft chose to mount the CPHSense instruments on 2 buses (Route 25 and Route 58). London Buses is a Transport for London contracted bus route in London, England operated by Tower Transit. Route 25 was chosen as it is the busiest bus route in London covering approximately 18.6 km. The second route selected was R 58, as this crosses over with the R 25 and runs in a less traffic intense area. Two Volvo B9 TL buses were fitted with CPHSense instruments and after evaluating the best fitment area the instruments were fitted vertically and a 24v power source. The power source was handled by connecting the Leapcraft sensors directly to the bus’s battery so that the devices were constantly powered when the bus was moving.

The bus routes were chosen in such a way that they intersected with the Oxford street automatic station regularly during their journey. This intersecting behaviour allowed the devices to calibrate against the stationary reference node. The CPHSense was programmed to collect pollutant data every 10s along with rapidly collecting GPS data at the same interval. There is a trove of open data from the London AQ Network and this was used to augment the data collected in order to verify the performance of the devices against the station.

The mounting position chosen on the bus was least likely to be affected in the event of a collision. They considered a nightly bus wash exemption for the trial vehicles to avoid unnecessary water ingress to the units although the units are heavy duty and weather proofed.

Bus Route 25 runs between Ilford and Oxford Circus and as of 2017, it is the busiest bus route in London covering approximately 18.6 km with 59 stops. Bus Route 58 runs between Walthamstow and East Ham covering approximately 12.5 km with about 48 stops. They intercept along the routes and this was used to continuously validate the data. The map also shows the co-location of the automatic monitoring stations.

The CPHSense, Leapcraft’s outdoor environment sensing device that was mounted onto the buses, is a high quality sensor for monitoring air quality at low costs combining electrochemical sensors, low noise signal processing and laser scattering of particles packaged in a unique and award winning design. This design enables the delivery of high accuracy in sensing gases and particles, maintaining a small footprint whilst being power efficient. The data was collected and sent to Leapcraft’s cloud servers to be processed for maintaining data quality and continuous benchmarking. The devices are designed to be mounted on moving vehicles creating the opportunity to have a mobile deployment strategy.

This London deployment is a key experiment in Leapcraft’s journey to map the state of the air. We have seen London’s air quality as a snapshot composed from mathematical models built on periodical data. It is not a map in real time. And that is a vital change. Having a chance to see the air change in real time will give scientists to ask new questions pertaining to exposure and health risks.

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