The ACCRA Project. Importance of accuracy in vehicle emissions estimation for urban dynamic geofencing.

Abstract

Five UK cities will implement clean air zones (CAZ) to improve air quality (AQ), specifically in relation to NO2
and 253 UK local authorities have declared Air Quality Management Areas for NO2. Vehicles which have an
internal combustion engine and an electric only range can offer zero emission (ZE) operation but cities lack the
ability to monitor and control the vehicles. Project ACCRA will address this problem.
The project is of 12 month duration aiming to develop and demonstrate a system that allows hybrid ICE/EV vehicles
to become part of a city’s urban traffic management control system; monitoring the vehicles’ location and operational
state, and able to control the ZE running strategy ensuring ZE through areas of poor AQ. Using a combination of
estimated emissions and air quality sensors the system’s decision-making engine will demonstrate the ability to
respond to pollution violations and modify (on-demand) the ZE strategy of the vehicle via active geo-fencing.
In order to support the decision on the dynamic geofencing, estimation of emissions represents an important and
fundamental step in the process, hence this paper focuses on the comparison of instantaneous vehicle emissions
modelling using traditional and low-cost GPS devices. A sensitivity test between the low-cost device (recording
frequency, typically 0.2Hz), and the more expensive recording at 1Hz has been performed. Results show that if
low-cost sensors were to be deployed in place of more expensive alternatives the emissions model underestimates
the total CO2 and NOx emission rates by a factor of between 5% and 20% depending on the vehicle and pollutant
type. The source of this divergence is identified as the sampling rate of the instrument rather than the low-cost
instrument. Hence, the deployment of low-cost, or specifically low resolution, sensors is only a suitable alternative
in situations where this margin of error is acceptable rather than a general solution.
This result will support further development of the dynamic geofencing within this project as well as will impact
vehicle tracking studies using methodologies other than GPS and CAN as it constrains the effective sampling rate
required by these methodologies to a minimum of 1Hz as well.

Original document

The different versions of the original document can be found in:

• https://zenodo.org/record/1491644 under the license http://creativecommons.org/licenses/by-nc-nd/4.0/legalcode

• http://dx.doi.org/10.5281/zenodo.1491644,

https://zenodo.org/record/1491644 under the license http://creativecommons.org/licenses/by-nc-nd/4.0/legalcode

• https://zenodo.org/record/1491644,

http://dx.doi.org/10.5281/zenodo.1491643 under the license http://creativecommons.org/licenses/by-nc-nd/4.0/legalcode

DOIS: 10.5281/zenodo.1491643 10.5281/zenodo.1491644