Reduced traffic congestion, cleaner air, and accessible public transport - cities are employing a variety of measures to make their transport systems more sustainable. Doctoral research by transport economist Zhiyuan Liang reveals that there is no single ideal solution. Traffic information, pricing mechanisms, and tradable permits can all be effective, but a measure that alleviates one problem may inadvertently create new ones elsewhere.
Liang investigated how travelers respond to information and policy interventions that influence their choices regarding routes, travel times, or modes of transport. His analysis encompassed not only traffic congestion but also emissions, exposure to air pollution, crowding on public transport, and broader societal impacts.
A key conclusion is that different modes of transport cannot be viewed in isolation. For instance, encouraging car drivers to switch to the metro might reduce road congestion, but it could simultaneously lead to overcrowding on trains. Furthermore, vehicle exhaust emissions can make cycling less appealing, which may, in turn, perpetuate a high level of car usage.
Traffic information can make a difference
Liang also demonstrates that providing high-quality information can be impactful. Data from a navigation app in Beijing suggest that traffic alerts are associated with shorter travel times and reduced exposure to traffic congestion. Consequently, navigation apps can play a valuable role by clearly warning travelers about issues such as traffic jams or accidents.
Financial incentives, such as road tolls, can also help to manage the demand for transport. Liang also examined tradable permits, a system in which travel opportunities can be regulated through an allocation of rights. Determining which approach works best depends on factors such as uncertainties surrounding congestion-related and broader societal costs, including infection risks, as well as the flexibility of the policy itself.
Implications for livable cities
The findings offer valuable insights for municipalities, transport authorities, and providers of navigation services. For instance, efforts to encourage motorists to switch to public transport must also account for the available capacity on metro and train networks. Similarly, when promoting cycling, it is important to consider not only the reduction in car traffic but also the level of air pollution to which cyclists are exposed.
Liang’s research demonstrates that sustainable transport policy requires a broad perspective. It is not just the number of cars that matters, but also how people respond to specific measures and how cars, bicycles, and public transport interact with one another. By accounting for these interdependencies, cities can develop transport policies that not only reduce traffic congestion and emissions but also better align with the needs and health of travelers.