Hoping to stimulate some debate about how the findings might apply to British cities:
Since Estonias capital started providing free public transport for residents in 2013, it claims to have turned a 20m a year profit each year. But has the scheme achieved its ambitions of reducing traffic and saving people money?
In London a monthly travel card for the whole city costs almost £200. In Copenhagen, a city a fraction of the size, youll pay £160. A pass lasting only five days in Paris will cost you over £60. So when you ask the residents of Tallinn about the benefits of free travel across the city, its a surprise to be met with a roll of the eyes or a sarcastic smile.
The capital of Estonia introduced free public transport at the beginning of 2013 after their populist mayor Edgar Savisaar called a referendum on the decision, dismissed by critics at the time as a political stunt that the city couldnt afford.
Three years on Savisaar has been suspended amid allegations of corruption, but the city remains committed to the programme claiming that instead of it costing them money, they are turning a profit of 20m a year.
To enjoy Tallinns buses, trams, trolley buses and trains for free you must be registered as a resident, which means that the municipality gets a 1,000 share of your income tax every year, explains Dr Oded Cats, an expert who has conducted a year long study on the project. Residents only need to pay 2 for a green card and then all their trips are free.
Since the scheme launched, an additional 25,000 people have registered in the city that previously had a population of 416,000, but this is where the tension lies. The more money for the city of Tallinn, the less there is for the places they leave behind, explains Cats, so its not hard to see why the government and the mayors office might see things differently.
Allan Alakula, the official spokesperson for the project, admits boosting the popularity of the mayors office was one of the key motivations for rolling out the project but insists that it was primarily about easing the burden on peoples wallets, and the citys roads.
The project took a year from inception to reality in which time Alakula and his team struggled to find cities to learn from. The city of Hasselt in Belgium had free transport for 16 years but they had to reintroduce fares when it became financially unsustainable. It is also free in the town of Aubagne near Marseille in France, but neither were on the scale of Tallinns ambitions.
Three years later the project has been inundated with requests from the Chinese city of Chengdu, home to 14 million and desperate to ease traffic congestion, to Romanias capital Bucharest. We would be happy to hand over the title of the free public transport capital of the world, Alakula laughs.
Tallinn is not a crowded or a big city, most journeys dont take longer than 15 minutes, and transport feels like its part of the citys furniture rather than something to be braved.
Drivers wait patiently as passengers cross their path to board a tram near Vabadus square in the centre of the city. It is nearing rush hour but everyone who needs a seat gets one. The trams and trains are clean and Tallinners have been enthusiastic about using them for free, with early polls delivering a 90% approval rating for the scheme.
Dr Cats, who is based at Delft University of Technology in the Netherlands, found that the number of people in Tallinn using public transport instead of cars was up by 8%, but at the same time the average length of a car journey had gone up by 31%, which he said meant there were more, not fewer, cars on the road in the time they tested.
He puts the increase down to a change in shopping and leisure habits rather than limitations of the scheme itself, and suggests that making driving more expensive, through parking fees and other taxes, could be more effective at cutting back on traffic.
So could cycling, which Alakula admits the city hasnt done enough to promote: less than 1% of people make their journey by bike, which basically means that cycle commuting doesnt exist, he says.
Cats also found mixed evidence whether the scheme has improved mobility and accessibility of low-income and unemployed residents [and] no indication that employment opportunities improved as a result of this policy.
According to Cats, free public transport is not the no-brainer everyone might initially think it to be. The idea still faces political opposition and visitors who use public transport are less satisfied with having to pay more for it than locals. But in the case of Tallinn it is almost exclusively used by residents, not tourists who rely on private buses, taxis and most recently Uber.
There is also a risk, says Cats, that free public transport could lead to less investment in the service. In the event of an economic depression, investment in public transport will be more exposed to potential budget cuts if they are not earmarked, he says.
Tallinn also cant rely on increasing tax revenues by attracting new residents forever. Before the scheme started, 6,000 new residents registered annually. And while the numbers shot up to about 10,000 new registrations in the immediate years after the scheme launched, early figures Alakula has seen suggest that only 3,000 to 4,000 have registered in 2016 so far.
But Alakula is positive about its longevity and says they have also been able to funnel money back to improve their networks. We are also in the process of building a tramline in to the airport that will get you there in 15 minutes.