The annual card, which costs €377, will contain an NFC chip, and was slated to be launched on March 1st.

However, the Wiener Linien transport provider told the Austrian Press Agency that the project has proved to be “challenging” and did not want to give a date when it might be released. “We want to focus on making sure that all the promised services are available for the launch and that it works properly,” a Wiener Linien spokesman said.

Michael Bauer, from the transport union, said that customer service employees would be faced with huge pressure if the card was introduced too early, as there would be many complaints if it didn’t function properly.

A standard yearly travel card for Vienna’s public transport network costs €365 – and will still be available for those who don’t want to upgrade to a mobility card.

When it is introduced, the mobility card will be available to order online, via the Wiener Linien website. It is designed to be used as a form of cashless payment in all Wipark garages, at Citybike stations and charging stations for electric cars, as well as for taxis. It will be linked to the customer’s bank account, and fees will be paid by direct debit.

The card will offer a discount of 14 percent on short-term parking tariffs and a ten percent discount for charging electric cars. People with a mobility card will be able to borrow Vienna rental bikes for an hour a day for free, and won’t have to pay the one-off registration fee.

Vienna has invested €2.5 million in the project.