When the Minnesota Bridge over the Mississippi river collapsed during an evening rush hour in August 2007, killing 13 people and injuring 145, the parlous state of America's civil infrastructure became headline news. Far from this being a rare event, apparently more than 130 American bridges collapsed between 1989 and 2000: that's about one a month. Europe's bridges seem more robust than those of the US, thanks to a more rigorous approach to inspection. Nevertheless, in August 2009 commuters using the BelfastDublin rail line had a lucky escape when part of a viaduct fell into the sea just after a train carrying 50 passengers had crossed it. Thankfully the train driver spotted subsidence and raised the alarm to halt any other trains on the line. Such catastrophic failures are boosting interest in embedding permanent sensors and communications links into all kinds of infrastructure to monitor it for structural deterioration. While safety is the main incentive, there is growing interest in how these techniques could extend the life of structures on the basis that the 'greenest' infrastructure is likely to be the infrastructure you repair rather than replace.