Handsets with touch screens, Wi-Fi and app stores are not only prolific, they’re primary traffic drivers, according to AdMob’s September Mobile Metrics Report. This month’s report marks the two-year anniversary of AdMob’s report.

According to September’s report, which is based on data from over 15,000 mobile Web sites and applications, over half of the top 10 devices were equipped with either touch screens, Wi-Fi or an app store. That’s a marked difference from last year, when the iPhone was the only touch screen device in the top 10.

According to AdMob, those specially equipped devices are “responsible for a much higher percentage of mobile usage than their share of handsets sold.” Essentially, smartphones are driving traffic.

The agency cites the worldwide growth of traffic over its network as evidence. Worldwide iPhone and iPod touch traffic increased 19 times from September 2008 to September 2009 in the AdMob network. In addition, 18 percent of requests in the United States were made from Wi-Fi capable devices in September 2009 versus 5 percent in September 2008.

AdMob also said Android-based devices posted a four percentage point increase from August, reaching 17 percent in September.

The AdMob Metrics report offers a monthly look inside the traffic flowing through the company’s network.