The largest US wireline operator, AT&T Inc, has said it is introducing data caps for its broadband internet customers, following on from a similar move by rival operator Comcast earlier this year. The monthly limits vary with the speed of the tariff, so a 768kbps service will have a 20GB monthly cap while the 10Mbps option includes 150GB of data use. The firm says it will begin trialling the new data caps with users in Nevada later this month, with a wider rollout to follow. Users who go over their data allowances will face a per-gigabyte charge. AT&T claims that 5% of its heavy-usage customers account for around 50% of the traffic on its internet networks and that this is unfair for other subscribers.