Spain

What the record shows

Most countries in this atlas buy their smart-city software. Spain writes it, and then other countries run it. Barcelona's council built Decidim in 2016 and by 2022 it had passed four hundred active instances in more than twenty countries, among them Mexico City, Helsinki, New York and the French National Assembly. Madrid's Decide Madrid produced the CONSUL engine, reused by more than two hundred and fifty institutions and now carried by a foundation of its own. Barcelona's municipal IT institute also released Sentilo, the open-source layer between its sensors and its applications, under a free licence — and other Catalan administrations, including the regional water agency, took it up. None of these came from a vendor. All three came from a city hall.

The awkward half of that story is what happened to the tools at home. Decide Madrid was pared back after the 2019 change of administration, which discarded approved proposals and halved the participatory budget it steers, from its peak to roughly half that today; few citizen proposals ever clear the vote threshold. Barcelona still runs its participatory budget on Decidim and publishes its own execution rate for the approved projects, which is a quarter. The code escaped and thrived. The politics it was built to serve did not travel with it.

That pattern — the instrument survives, the mandate is contested — runs straight through Spain's best-evidenced policy, the low-emission zone, where the fight has been legal rather than technical from the beginning. Madrid Central launched in November 2018, was suspended by the incoming mayor in 2019 and reinstated by the courts within days, had its founding ordinance annulled by the Supreme Court in 2021, relaunched citywide, was annulled again in 2024 on procedural grounds, survived a Supreme Court refusal in 2026 and was re-approved that March. Barcelona's ring-road zone covers more than ninety-five square kilometres across five municipalities and had its enforcement suspended for two months in early 2026 during a regional rail crisis, then switched back on. Through all of it the measurement kept arriving: an independent study by ISGlobal with the city's public health agency and a national research council institute found nitrogen dioxide down by nearly sixteen per cent at traffic stations inside the Barcelona zone, using a synthetic control against a modelled no-zone scenario.

Spain also produced the cleanest documented retreat in the whole atlas, and it is worth reading as a success rather than a failure. From 2011 Barcelona embedded in-ground parking sensors — a hundred in the innovation district, five hundred more in Les Corts — and they became one of the most-cited smart-city showcases anywhere. The city never scaled them. It built a payment app instead, and from 2017 predicted where the free spaces were from the payment data itself, keeping physical sensors only for niche uses such as tourist-coach bays. An inference replaced an installation. Madrid took the same logic further in the other direction: its regulated parking reads the plate, queries the national vehicle registry and prices the space by the car's emissions label, with zero-emission vehicles parking free and rates climbing on high-nitrogen-dioxide days. The sensor there is the registry.

Underneath the software, Barcelona keeps a physical layer that predates all of it. Vacuum pipes have carried household waste out of several districts since the 1992 Olympic Village, and they are still district-scale rather than citywide more than thirty years on. The 22@ plan rezoned two hundred hectares of industrial Poblenou in 2000 and laid dark fibre, pneumatic collection and district heating under thirty-seven kilometres of street — the ground the later pilots were run on. It is also the entry that keeps the country honest about delivery: a peer-reviewed review of its first fifteen years found roughly a third of the promised social housing built and half the district's land still awaiting transformation.

Two more things are distinctive enough to name. Barcelona is the atlas's clearest case of residents measuring their own air and out-sampling the professional network while doing it: the 2018 xAire campaign put roughly sixteen hundred volunteers on seven hundred and twenty-five points across all ten districts, peer-reviewed, and found hotspots above the limit. And SmartSantander, a small northern city, hosted about twelve thousand sensors for an EU research testbed between 2010 and 2013 and became the reference other cities cited for years — an experiment that ended on schedule and left its reputation behind rather than its infrastructure.

Read together, the Spanish record is unusually generous. Its cities gave away the participation platform, the sensor middleware and the testbed methodology, and kept the harder problems: a court that keeps annulling the clean-air ordinance, a superblock programme that stopped expanding on cost and had part of one axis ordered reverted, and a fare system, T-mobilitat, that took roughly eight years and tens of millions in overruns to replace a cardboard ticket. What Spain exports is the easy part to copy. What it is still working on is the part nobody can install.

Sources beyond the atlas

Facts above that do not come from a linked entry rest on these:

• Consul Democracy Foundation — the body that now maintains the engine built for Decide Madrid
• Decidim — the project's own account of the platform Barcelona City Council released