Traffic congestion charges could fail to cut emissions and congestion unless realistic alternatives to driving are in place, a University of Auckland academic says.
Dr Hyesop Shin, a lecturer in environmental science, says new legislation allowing councils to introduce congestion charging has the potential to reduce vehicle use, traffic jams, air pollution and greenhouse gas emissions, but only if supported by strong public and active transport options.
“Congestion has so many harmful impacts, because lots of emissions are produced while vehicles pile up,” Shin says.
“However, congestion charges could increase emissions if people take detours and end up driving longer distances to avoid toll points.”
Shin is providing research to Auckland and Wellington city councils on the potential impacts of different congestion charging schemes. His team has recently completed a study modelling Auckland traffic under a cordon-style charge around the central business district.
The modelling suggests some drivers would reroute to avoid paying, potentially creating new bottlenecks.
“If the charging system doesn’t anticipate drivers taking detours, it could create new congestion points, increase noise and emissions in local neighbourhoods, and push traffic onto roads not designed for heavy use,” Shin says.
He says councils would need to closely monitor areas near toll points to ensure diversion routes do not create health impacts through increased air pollution or noise, particularly in residential areas and near schools.
Auckland Council is considering six different congestion charging options, focused on the city centre, highways leading into the CBD, or a combination of both.
Shin says his team is using computer modelling to assess how different charging scenarios could affect people across income levels, ethnic groups, ages and neighbourhoods.
“We’re concerned about equity, and whether congestion charges place an extra burden on people living in areas with higher deprivation,” he says.
Shin says higher-income commuters may simply absorb the cost and continue driving into the CBD, while lower-income workers without access to public transport could be more heavily affected.
Some may change work hours, park outside the city and walk or bus in, or face higher commuting costs overall.
If implemented carefully, Shin says congestion charges could encourage greater use of public transport and active modes such as cycling, scootering and walking.
“If more people are exercising as part of their daily travel, that will have significant health benefits.”
The study found travel times into Auckland’s CBD were around 50% longer during peak periods from Tuesday to Thursday, with traffic flowing more freely on Mondays and Fridays as more people work from home.
Traffic volumes were higher on rainy winter days, while most morning peak congestion originated from suburbs close to the city centre, including Grey Lynn, Mount Eden and Remuera.
High volumes of traffic were also recorded from South Auckland on midweek days, while state highways from the west and north were busy but less intense.
Shin says international examples are being examined as part of the research, including New York’s congestion charge, which introduced a US$9 fee between 5am and 9pm and reduced traffic volumes by an average of 11% over six months.
