On call across the river

According to UN forecasts, 70% of people will live in cities by 2050. However, these only occupy about three percent of the earth's surface. It doesn't take expert knowledge to realise that such an uneven distribution of space can cause problems - already, inner-city roads often move beyond their capacity limits at rush hour. A team from Stockholm is working to realise the potential of reclaiming waterways that already exist. At the same time, designers around the world are already presenting designs for what sustainable urban water transport could look like and what benefits it could bring.

According to a study published in 2021 by the International Transport Forum of the OECD , the volume of traffic will more than double by 2050. According to the study, passenger traffic will increase 2.3 times and freight traffic 2.6 times. An end to traffic congestion in metropolises thus does not seem to be in sight.

While for a long time attempts were made to counteract higher mobility needs by expanding the road network, transport planners are now in agreement: more roads do not reduce the risk of congestion, but actually increase it in the long term. A study by the US organisation T4A , among others, provides data on this. Rooted in economics, this phenomenon is called "induced traffic" in the technical literature. If the price of a good decreases, the demand for it increases; if the traffic situation of car drivers is improved, people will travel more often and further by car. Or, as citizens' initiatives and environmental associations have been saying for decades: "Those who sow roads will reap traffic.

Continuously expanding the road network and adapting it to the increasing mobility needs in urban areas does not seem to be a sustainable solution. This idea was the intention of Susanna Hall Kihl from Stockholm to found Vattenbussen in 2009, which translated means "the water bus". The NGO aims to raise awareness of water as an urban transport mode. In cooperation with the Royal Institute of Technology of Sweden, it has since been researching how the capital's numerous river connections can be integrated sustainably and efficiently into local transport by using ecological water buses or taxis. According to Karl Garme of the Department of Aeronautical and Automotive Engineering, five things need to be considered for such concepts to improve transport capacity in cities:

• Connection to land transport infrastructure both physically and via integrated booking options,
• year-round, reliable operation,
• fast and uncomplicated boarding and disembarking without waiting times
• energy efficiency, effectiveness, modularity and sustainability, and
• early planning.

The city where the use of water buses in everyday life is probably best known is Venice. The ferries, known as "vaporetti", which have an average capacity of around 200 passengers and operate in a comprehensive system of routes, connect the city districts day and night. Venice does not have a road network - at least in the centre - which is why the use of the canals is without alternative. Similar boats are also in operation in Hamburg, Vienna and Berlin, but there they are used more for tourist purposes than for everyday commuting. They do not appear in the modal split, i.e. the percentage distribution of passenger kilometres travelled among the means of transport used.

In Indonesia, an archipelago of more than 17,000 islands, sea routes are more likely to be part of the transport network - albeit less firmly anchored than might be expected given the island's geography. Current data is not available, but in 2002 the share of passenger kilometres travelled by water was less than one per cent. The number of ports open to the public was 111 in the same year, and according to Statista it was 294 in 2019, so it is possible that the share of water transport in the modal split has increased within the last two decades. Nevertheless, a large part of the potential remains unused: About two-thirds of the state's surface area consists of water.

Some designers have already presented innovative concepts to advance the development of urban water transport. The French company SeaBubbles , for example, has been producing so-called "hydrofoils" since 2016, boats the size of a small car that are powered exclusively by green energy and produce neither noise nor emissions. Digitally reservable via app, they take four passengers on-demand at around 30 km/h from A to B. They have already been tested on the Seine in Paris since 2017.

Only recently, Duffy London developed the " Hari Pontoon ", a bamboo boat powered by solar energy, which is to supplement the local water transport infrastructure in cooperation with an Indonesian company. It offers space for about 15 passengers and can also be used for smaller goods transports. According to the manufacturer, the electric motor, which is constantly charged during the journey, has an output of about 60 hp and reaches a maximum speed of about 20 km/h.

While the "Hari Pontoon" requires a workforce of two, Crosswater Technologies from Silicon Valley is trying its hand at an autonomous on-demand system that also holds about 15 passengers. 1,000 journeys should be possible with a single charge, the company announces - also noise- and emission-free.

Innovations like these make it clear that Susanna Hall Kihl struck a chord with her idea in 2009. The use of existing river and canal systems may well become a market: At the latest when the roads become even more crowded. The future will show whether SeaBubbles & Co. have the potential to become permanent components of the inner-city transport infrastructure.