AT&T reports wireless traffic has reached new records, but the greatest growth isn’t on the company’s mobile data network, it’s coming from Wi-Fi.

Through a combination of delivering faster service over Wi-Fi and AT&T’s Internet Overcharging usage caps, speed throttles and overlimit fees, AT&T customers are increasingly turning to Wi-Fi connections on their mobile devices.

In the last year, traffic has tripled.  In the third quarter, AT&T reports 301.9 million connections to AT&T Wi-Fi, more than five times the number of connections made during the whole year in 2008.

AT&T Wi-Fi is turning up in partner retail outlets, restaurants, coffee shops, and in gathering spots for large crowds, such as major metropolitan shopping areas, stadiums, and parks.

With the advent of AT&T Wi-Fi, customers can drop their 3G data connections and avoid traffic eating up their monthly usage allowance.  Wi-Fi can also deliver faster connections and more reliable service.

Wi-Fi can deliver benefits in urban congestion zones, where ordinary 3G/4G cell tower sites can become overwhelmed with traffic during peak usage times or during major events.  It’s also cheaper to deploy than upgrading traditional cell towers to handle larger amounts of congestion.

That’s a combination that works well for AT&T, who is the most aggressive carrier by far in pushing customers to use Wi-Fi.  Neither Sprint, Verizon Wireless, or T-Mobile come anywhere close to the number of mobile hotspots available.