A congestion sensitive approach to modelling road networks for air quality management (Abstract, James O'Brien; Anil Namdeo; Margaret Bell; Paul Goodman, Int. J. of Environment and Pollution, Dec. 2014)
Also discussed here: Stop-start driving in city centres creates higher pollution levels (Phys Org, Dec. 12, 2014)
And here: New regional traffic model to combat urban road congestion (Phys Org, Jan. 9, 2014)
And here: Verkeersvoorspellingen met modellen: een voorspelling over modellen (in Dutch language) (3 page pdf, Victor L. Knoop and Serge P. Hoogendoorn, Nationaal verkeerskundecongres, 6 Nov. 2013)
Today we review research into improved modelling of emissions from congested traffic which takes into account instantaneous starts and stops instead of assuming a constant speed of vehicles. The results indicate that previous mobile transportation pollution models may underestimate emissions by as much as 60%.and this has large potential consequences for environmental impact assessments of large transportation projects, as well as for regulating or reducing emissions from currently congested cities.
“Traditional methods of modelling traffic pollution could be under-estimating emissions by as much as 60%”
“Previously, traffic emissions models have only looked at the average speed of traffic as a whole and assumed traffic was travelling at the same speed at the same time, ignoring the stop-start related vehicle emissions often associated with congestion.”
“The new technique, called PITHEM (Platform for Integrated Traffic, Health and Environmental Modelling), looks at congestion emissions based on individual vehicle type, its speed and acceleration and, crucially, takes into account meteorology and local terrain”
“Findings from microscale modelling have revealed that the use of an IEM [instantaneous emissions model ]to calculate emissions as an input for air quality dispersion modelling significantly improved the performance of the dispersion modelling when measured against monitored data. Findings from microscale modelling have revealed that the use of an IEM to calculate emissions as an input for air quality dispersion modelling significantly improved the performance of the dispersion modelling when measured against monitored data.”
"Whereas previous models looked at 'steady state' traffic conditions, in reality, during peak hours congestion vehicles often decelerate and accelerate and move at different speeds, especially when the road goes up or down hills.”
"By gaining a better understanding of how road networks are influencing emissions, councils can make more effective decisions about how to deal with congestion in our city centres and help reduce the 50,000 premature deaths in the UK each year that are associated with traffic emissions."
“The model currently only works with cars, but Knoop and his colleagues hope to be able to integrate pedestrians and cyclists into it in the future. He is also hoping to expand the tool in order to calculate emissions.”