Public transport has long been touted as a greener way of getting around major towns and cities, but this has largely lacked any empirical evidence to support the claim. New research from the University of Utah has attempted to plug that gap by quantifying just how much public transport reduces pollution.
The researchers collected data from the contactless payment systems installed on buses and commuter train services in Utah to not only provide a decent estimate of the emissions currently saved, but also how much could be saved with better coverage.
The data collected allows them to understand where riders enter and exit the public transport system, which even though not all passengers use the technology allows the team to provide a reasonable estimate of total usage patterns.
“Now we can truly quantify trips in both time and space,” they explain. “We accounted for all of the 2016 passenger miles by scaling the farecard data, and we know which trips farecard holders make on buses, light rail and commuter rail.”
They combined official data with data from the General Transit Feed Specification system that feeds places like Google Maps with transit information.
Greener transit
The researchers were able to quantify the emissions produced per mile traveled via public transport, before estimating the amount of car travel avoided via the public transport usage.
There were clear environmental gains during rush hours and in densely populated areas, with these gains then tapering off during evening and weekend hours and less populated parts of the city. For emissions to be positive for longer periods of time would require more riders per trip, cleaner vehicles or fewer journeys with minimal riders.
Of course, the transport network in Utah operates with a significant legacy fleet, with some buses around 20 years old, and many trains low down the emissions scale. The model developed by the team enabled them to test the impact of upgrading to a greener fleet, and therefore provide a cost/benefit analysis to planners and the Utah Transit Authority (UTA).
“Now, with this information, UTA can go to stakeholders and funding agencies and say, ‘Look, we’ve done this analysis,” the researchers explain. “This is how much less we can pollute.'”
